Category Archives: Uncategorized

Primer on Precise Radial Velocities

Objects in space are specified by their Right Ascension, Declination, and distance.  The first two are easily measured, usually to better than a part in a million; the last is notoriously tricky to measure, sometimes uncertain to an order of magnitude.

The time derivatives of these quantities are the reverse: proper motions are unmeasured for most objects in the universe, but velocities can usually be measured to a part in a million rather easily.

I noticed this (I’m sure I’m not the first) when writing a review chapter on precise radial velocities as an exoplanet discovery method. I think it’s a good primer on the subject for students just getting started.  In it I briefly trace the origins of the method to the fundamental importance of radial velocities to astronomy in general and spectroscopic binary star work, then work through the high-mass-ratio limit of SB1s, the first exoplanet discoveries, and the future of the method.

There is also a quick section giving what I think is a fair overview of the problem of stellar RV jitter, including the roles of surface gravity, granulation, oscillations, and magnetic cycles.

You can find it here.  Enjoy!

Good Advising

Chanda Prescod-Weinstein wrote a valuable article for students on the warning signs of being psychologically abused by your professor.

Sadly, some advisers abuse their advisees in various ways: emotionally, physically, and sexually. This exists on a spectrum, of course: a few are serial predators, but there is a long tail up towards people who are just jerks, to people who are generally good but have some blind spots, and so on. I thought her list was a good way to help not only identify abusive professors, but to “score” professors on something like such a scale.

Reading this, I thought about which of my uncodified advising strategies encourage or discourage each of the warning signs. I then used Dr. Prescod-Weinstein’s article’s framework to try to write down what advisers should do instead—these rules both help avoid abuse of advisees, and also (I think) lend to good advising.

This list represents my own, aspirational opinion on good advising having now graduated my first “round” of students and postdocs. Some of these items are just “do the opposite of that item of Chanda’s list,” and others are inspired by my own experiences with advisees and their advice to me. I know I fail at many of these (some of those failures inspired some of these points, actually) and some I only really thought of while compiling this list, so they are new aspirations for me.

This list is meant as a complement to Chanda’s: a resource more for advisers who want to improve their advising (or, at least, strive for a style similar to the one I strive for) than for advisees to understand when they are being abused. 

Please leave your own ideas and thoughts on these ideas in the comments.

1) Praise your advisees

Say “good job” when they do a good job. Say “I like that” when they do some work you like. Say “good idea” when they have a good idea. Tell other people, in your advisees’ presence, what your advisees are doing and why you like it.

It can be hard to remember just how hard graduate school is. It is a huge amount of very slow work at a the highest intellectual level sustained for a long period of time. Encouragement is essential, and it’s easy as an adviser to forget that it needs to be explicit or it’s not there at all.

This comic resonates because this is how it feels to get any criticism about your work on a paper. Think about how you feel when you read an anonymous referee’s report: recall how it was way worse than that to get that sort of feedback from your adviser. Don’t make your advisees ask for the parts you liked; lead with that!

Note: I meant it when I wrote “good”; I did not mean to write “great”, ”outstanding”, or “genius”. Even ordinary, pedestrian steps in research are “good” because graduate students and postdocs are pre-selected to be good at research. Give your advisees a sense for what constitutes good work by telling them it’s good work. If you keep the carrot dangling in front of them in a vain effort to keep them striving for better, you’ll give them a twisted sense of what good research looks like. Give them the carrot.  

2) By default, set a positive tone with your advisees

Set a positive tone in personal and group meetings. Make smalltalk (real smalltalk; see points #10 #12 and #13). Don’t frown, scowl, or shake your head as a matter of course. Give criticism constructively and only after saying what you like about something (see point #1.)

3) Take real interest in your advisees’ projects and let them know their projects can succeed

Fist of all, remember what the project is, and where they are with it! Especially for very independent students or when things get very busy, it is surprisingly easy to lose track of what an advisee is working on. 

Even if you don’t know how their project will turn out, find the value in the results they have and state it. See point #1.

Tell others about your advisees’ work and how you’re excited about it. See point #2. If you are not excited about a student’s project, either they need a new project or they need a new adviser.

Show your interest by staying involved with the project. Meet with your advisees regularly (something like weekly, according to their level of independence and need) and monitor their progress. When they send you an email about their work, prioritize that email along with emails critical to your most important projects.

Jorge Cham’s PhD Comics can be a good way for students to commiserate and laugh about the difficulties of graduate school, but don’t let them normalize poor advising. Yes, we are supposed to recognize our advisers’ foibles in Prof. Smith (my PhD adviser once suggested a qual topic for me—months after I had passed my qual and was working on my thesis!) But remember his behavior is not supposed to be a normal part of graduate school.

4) Value your advisees’ opinions

Your advisees will disagree with you. Unless you’re sure they’re wrong for a simple reason (in which case be friendly and didactic about it) take these disagreements well and respect their opinions.

Think of it this way: either they are wrong or right. If they turn out to be right and you valued their opinion, then they will gain insight and confidence from the experience. If they turn out to be wrong and you valued their opinion, then they will gain insight and humility from the experience. Either way, you were a good adviser.

But if you belittle or ignore their opinions, then if they turn out to be right, they’ll be bitter, and if they turn out to be wrong, they’ll be demoralized. Either way, you could have handled it better.

5) Admit when you’re wrong.

“If you aren’t making mistakes, you’re not doing anything” Show your advisees by example how scientists make productive mistakes (and yes, even unproductive ones). This helps bust the “cult of smart” and teaches what science looks like.

This is especially important if an advisee was involved in the mistake. Make sure your advisees don’t feel blamed for your errors. Take responsibility for your share of being wrong, especially since you are responsible for your advisees’ research. If you screw up with something that makes their life harder, bite the bullet and make it right at your own expense—don’t make them deal with your mess. 

6) Tell your advisees to talk with other professors

Especially your undergraduates. One of the biggest confidence builders is to go to an expert and have a conversation with them about your research where you know more than them, they are interested in your work, and you have interacted as experts do. This also helps break down “cult of smart” myths by humanizing our heroes.

7) Encourage your advisees to start collaborations with other people

Science is a social endeavor. If you’re not sure where to start, start with collaborations within your group, then with other groups in the department, then beyond. Networking is an essential part of professional development. Introduce them to other groups and expect them to collaborate. Send them to meetings with a list of people to meet, and let those people know that your advisee will be there.

Also, many projects require expertise far beyond what you have—astronomy is very collaborative.  When such an item comes up, use it as an opportunity to get your advisee working with an expert on that topic. Introduce your advisee by email, make sure that expert has your advisee on their colloquium-day schedule, send your advisee to their institution for a day to learn that software, schedule a telecon to discuss the issue with your advisee sitting next to you.  Make your network their network.

8) Encourage your advisees to try things independently

Allow them to carve out a fraction of their work time to experiment without your close supervision. This is how they grow as advisees—they won’t be your advisees forever, and independence is something that should be taught and nurtured, not expected to magically appear once they graduate.

An important part of growth as a scientist is having ideas for new projects, so it’s important to encourage your advisees to identify new paths forward. Since most ideas are bad ideas, this means hearing ideas you know won’t work but encouraging the brainstorming exercise anyway. See point #5.

If their idea is too ambitious, keep it real without shooting it down. Aspirational projects are good projects, and students will often surprise you with how far they can take a project. Give them what you think they need to succeed, a realistic timescale for how long it will take, and let them shoot for the moon.

9) Let your advisees have lives outside of work/school, and let them know you don’t disapprove

Take a positive interest in your advisees’ extracurricular activities when they bring it up, but don’t pry. Mention your own extracurriculars to show your advisees that scientists can have outside interests. Be supportive of them having interests outside of work (even if you personally think they are making a mistake). This includes family matters— your job is to support their goals against the background of their family situation, not pass judgement on how to change their family situation in support of their goals.

Also, culture of science activities (communication, governance, inclusion efforts etc.) are not extracurricular. They are service to the profession (which, by the way, are part of the criteria on which faculty are judged for tenure). Support that as part of their professional development, even if it’s not the sort of service you would do yourself.

It is, of course, important to make sure advisees understand time management, have realistic timelines for completion of projects, and know what is needed from them for them to achieve their goals. But this does not mean you should disapprove that their timeline is longer than you would like it to be, and it certainly does not translate to micromanaging their personal time.

This means that except for coodinating while on observing runs or rapid follow up of transients or the like, it’s usually not even necessary to know your advisee’s cell phone number. Email, internet instant messaging, and group chats like Slack are perfectly fine ways for most advisers to stay in touch. A call on a cell phone carries an implication that they need to respond immediatey; especially outside of normal business hours, a student needs to be able to decide privately if and on what schedule they will respond to you.

10) Respect your advisee’s privacy

Unless they go missing for several days without notice or you are otherwise genuinely concerned for their personal well being, don’t snoop. Don’t cyberstalk, don’t contact their friends and ask where they are, don’t try to learn about or participate in their extracurriculars, don’t monitor when their “online” light turns green on social media, and don’t keep track of how often they email you at odd hours.  Your advisees are not your young children and you are not their guardian; they are adult colleagues in charge of managing their own time and personal lives.

That said, you are one of the first people in your advisees’ lives that will notice if something is wrong (and grad school is hard—things often go wrong). When this happens, you need to notice, you need to be there to support them in a professional way, and you need to ask how you can help. But don’t confuse that with snooping.

I used to think social media muddled this issue, but most platforms have privacy controls that let your advisees prevent you from seeing anything they’d like to keep from you. If you connect on social media (“friending”, “following”, etc.) make it clear that you expect that they will use those controls to maintain the level of privacy they want (i.e., you won’t snoop, and they shouldn’t feel bad having lives you don’t know about).

11) Accept your advisees’ judgements about what they need and how they feel

Make sure your goals for your advisee are consistent with their goals for themselves. Your advisees aren’t you. You are not printing out copies of yourself. Your advisees have their own priorities, values, and goals. Help them realize those, or else get out of the way.

This means that if your advisee tells you that they want you to change your advising style or stop behaving a certain way, don’t take it personally and don’t chastise them for it. If you really don’t want to accommodate them, think about why and whether they need a new adviser. Don’t tell them they’re wrong about how they feel and definitely don’t blame them for hurting your feelings.

This also means if an advisee is not working well with someone or has some personal reason for not pursing an opportunity you think is great, trust them. If they tell you they’ve been treated poorly by someone else, believe them.

This is especially true if they tell you they’ve been harassed or discriminated against in a way you haven’t been. They know better than you, and it is your job as their adviser to support them. If as soon as an advisee tells you they have been mistreated, you suddenly become an independent, objective trier of fact protecting the rights of the accused, you are not being a good adviser. Don’t interrogate them about whether they are sure or how they must have misinterpreted—guide your reactions by the premise that what they are saying is true. This can be especially hard if they have been mistreated by a colleague with whom you are on good personal terms. Do it anyway.

12) Keep the advisee-adviser relationship professional

Some advisers and advisees become lifelong friends. Others don’t (quite the opposite sometimes). That’s fine—it’s the same with any colleague. But no matter what, you have a professional obligation to support your advisees careers consistent with their goals.

This means keeping the relationship professional while they’re your advisee. Even if you’re becoming good friends (or the opposite) your advisee needs your objectivity, and the profession needs your professionalism as long as an advisee-adviser relationship exits.

Note that “professional” doesn’t mean “distant and unemotional.” It’s fine and good to have fun when with your advisees—group celebrations at your house or downtown etc.—and I consider it good practice to acknowledge the joy, pain, frustration, nervousness, and other emotions scientists feel as part of their jobs.

This all means different things to different people. Different advisers have different styles, and that’s fine. Rules on things like hugging, one-on-one lunch (or dinner) discussions, drinking together, leaving the office door open during meetings, and so on will vary from adviser to adviser and advisee to advisee, and will depend on factors like each person’s cultural background, comfort zones and personal space, familiarity with the other person, environment, and a lot more. It’s complicated because science is a social endeavor and social interactions among people are complicated, and hard or impossible to codify.

But no matter who you are, you should not lean on your advisees for emotional support (they may need yours, though), and certainly you should not discuss sexual topics. If you find that your advisees are the only place you have to go for such interactions, you need to remedy that situation or stop being an adviser.

Finally, some advisees will come to you with personal issues, from minor home-life matters to major life crises.  This rule should not be construed as saying that you should avoid helping them. The personal often becomes professional, and it is your professional obligation to help the students through it by supporting them, encouraging them, and giving them the tools they need to succeed (see #15). It is often a “last-chance encounter with a faculty member who [takes] the time to listen and give support [and] encourage[] them to hang in just long enough to surmount their immediate problems, and to persist” that keeps a student in the field.

But while it can help to open up here about your own experiences, this is not an opportunity to stop being professional. Indeed, it’s the time when your advisee needs your professionalism the most.

13) Respect your advisee’s personal characteristics

Unless you are very sure that you are on sufficiently familiar terms with the advisee that you will not give offense, avoid any comments about any personal characteristics, except perhaps for obvious platitudes (acknowledging a new haircut or injury, for instance). Especially avoid comments about uncontrollable aspects of their physical appearance, body parts, race, gender, sex, sexual orientation, pronouns, disability, mental health, religion, or family. Obviously negative comments are bad, but even positive comments can be gauche or misinterpreted.

It might be tempting to frame such advice as guidelines for professional behavior (“I don’t think you should give your dissertation talk with your hair dyed that color”; “people will find that tongue stud distracting”), but strongly resist such “advice” except when you really think it’s essential and the advisee genuinely does not appreciate the concern you have (“profane T-shirts are not appropriate at group meeting”).

This does not mean that you should not “see” race, gender, and other personal characteristics. You and your advisee need to be aware of how society’s perceptions of these identities will affect your advisee professionally, and this can and should be a topic of discussion. As an adviser you also need to be aware of and respect how your advisees are affected personally by these identities, especially those you do not share. But have these important conversations in a general way and let the advisee insert themselves into the topic, instead of presuming to know how they relate to their own identities.

14) Model professional behavior, even when it isn’t strictly necessary

Imagine that among your advisees are potential future bad advisers, and teach them by example every day not to be that way.

I had some downtime after the birth of one of my children in the hospital while the baby was asleep, so I opened up my laptop and started working. My wife very wisely suggested that I not send any emails to any of my group members lest I imply that I expected people to work even the day their kids are born.

So even if you’re buddies with a colleague, use a professional register when emailing them and your advisees are cc’d, give a proper not-embarrassing introduction before their colloquium, and save the not-for-the-office banter for when you’re not in the office.

Set a good example for all of your advisees in group meetings by being maximally professional. For instance, ask questions respectfully, disagree gently, don’t interrupt (especially don’t interrupt quiet people, women, or others that are often inappropriately interrupted), and don’t let others interrupt, even if you might have a more free-wheeling conversation with that person in a one-on-one setting. Don’t let your advisees behave rudely—model how you hope they will act when they see inappropriate behavior at, say, a conference.

Candid shot of a typical weekly meeting with one of my students as we deal with a referee’s report.

15) Be your advisees’ advocate…

Fight for your advisees’ future. Find out what they want, what (other than themselves) is stopping them from getting there, and how you can remove those obstacles. Ask what you can do, listen to what you’re told, and do it. Bring up their work with your colleagues. Introduce them to important contacts at meetings. Use your weight to help them win bureaucratic battles.

16) …and do it transparently (i.e. don’t be a puppetmaster).

Strive to only have conversations about your advisees you would be comfortable having them overhear. Make sure they know about and approve of any plans you have for them. If you are working behind the scenes, greasing wheels, or machinating for their benefit, keep your advisees fully apprised of your actions (except where you are bound by some sort of confidentiality). This includes mentioning them as job candidates, suggesting they work with a collaboration on a project, and getting funding to support them. Pulling back the curtain shows your advisees how science works and lets them know that you are working in their interest, and lets them give you feedback on your efforts.

16 points is a lot to remember, but Sharon Wang boiled them down to specific examples of the two indispensable, orthogonal qualities of a good adviser: respect and responsibility. If you are embodying these qualities in all of your interactions, you’re probably doing all right.

This list has benefitted from input from Fabienne Bastien, Sharon Wang, Angie Wolfgang, and Jason Curtis.

Star-Planet Interactions, and Jupiter Analogs

Waaaaay back in 2015 the International Astronomical Union held its General Assembly in Honolulu. I went and gave a review talk on star-planet interactions at a Focus Meeting.

One nice thing (in the long run) about these Focus Meetings is that they generate proceedings that get published. It’s sort of old-fashioned now, but it’s still nice to see these proceedings because they often contain things not in refereed papers: preliminary, unrefereed results that turn out to be important later, and overarching but concise syntheses of lots of work in a way that is useful for understanding but not really appropriate for a refereed article on novel research.

(I write “in the long run” above because having to actually write the proceedings can be a pain, and because they seem to take fooorrrreeevvvveeeerrrr to finally get published.)

Brendan Miller

Well, I was going through my CV for my end-of-sabbatical report (7 more days!) when I remembered that Brendan Miller and I put in a proceedings for the 2015 summer meeting!  Whatever happened to it?  Turns out it was published a while ago and somehow I missed it (which is weird because I have a copy of that book on my shelf…)

Anyway, our contribution is now belatedly on the arXiv.  Here’s what’s in it:

We really want to study the magnetic fields of exoplanets. It seems sort of hopeless—magnetic fields don’t have that much energy and it’s hard enough to figure out a planet’s mass, much less this little detail—but there is hope.

One hope is that close-in exoplanets will have their magnetic fields interact with their host star’s magnetic fields, causing magnetic activity on the star that we can detect in the calcium H&K lines. There had been suggestions in the literature that this was happening, as magnetic “hot-spots” beneath close-in planets rotated in and out of view, but follow up of those systems found the effect to be difficult to reproduce.  I think it was noise.

Another hope was that there was an overall increase in the level of activity in stars with close-in exoplanets.  If you took a sample of stars with and without close-in planets, were the ones with close-in planets more active?  Turns out that’s hard, because there are lots of biases in the way we detect close-in planets (via transit) that might make it more or less likely to find them around active stars in the first place.  Brendan and I wrote a paper where we looked at the evidence (and gathered some ourselves) and concluded there’s no signal to we can dig out of all of the noise.

But there are clear cases where there is star-planet interaction, just by another route: close-in, very massive planets seem to be able to spin up their stars, which makes them more magnetically active.  That probably drives the small amount of correlation we do see.

Then Brendan took a look at WASP-18, which should have one of the strongest planet-induced activity levels around if that’s a thing, and found it’s not elevated in X rays.  Bust there, too.

One thing we did not have time or space to touch on in the article was the one way that magnetic fields do seem to have been detected, via bow shocks., which is a shame but was fortunately covered later in the session.

There is one more bit in the paper that has been dribbling out slowly over the past few years, too. One of my earliest interesting papers was announcing the discovery of the first really good Jupiter analog HD 154345 b.  It’s around a G star, has about an 8 year circular orbit, and is around one Jupiter mass.

One gotcha is that the planet has the same orbital period (and phase!) as the star’s magnetic activity cycle. That’s not too surprising: stars’ cycles tend to be around 10 years, and so some will inevitably have planets at similar periods. The phase matchup is a further inevitable coincidence. After all, our stablest stars, like σ Draconis, have big strong magnetic activity cycles and those don’t create phantom planets in our radial velocity measurements.

Or so we argued in the paper. Well, since then, the coincidence between activity and RV has been getting better and better, and as early as seven years ago I had been conceding that this might be a rare, strong activity-RV coincidence.  I mentioned it in at the first EPRV Workshop (you can see it in the slides here) and again at the 20th anniversary of 51 Peg conference in Haute Provence.

Well, here it is again, in our review:

This is one of those cases where I really should get this into a refereed paper, but I’m busy, and more data will make the case stronger, and retractions are hard to get motivated to write.  Anyway, this has been out there for a while in unrefereed form (and actually disputed! though I still think the planet is probably wrong) but I hope to get it properly written up this fall.

Anyway, that’s the news from Lake Wobegon, where all the planets are Earth-like, all the objects are Rosetta Stones, and all the signals are significant.


Clickbait and Sensationalism

Journalism has been in trouble since… well maybe since forever but it certainly feels more precarious since the World Wide Web destroyed most print journalism as a viable stand-alone business. The New York Times and Washington Post have hung on with quality journalism, but not without moving to a heavy online presence and worrying a lot about generating “clicks” (at least on the business side).

One way to survive is to generate lots of those clicks, and that means “clickbait”—provocative headlines that dare you to ignore them. Whether you find this to be outrageous or just a fact of business probably depends on how exposed you have been to it.  I imagine most journalists take it as a given that headlines and ledes must generate clicks and scrolls in order for them to have jobs, but that what really matters is the meat of the article.

It would be nice if it weren’t so, especially when it’s your science being hyped. Yesterday I wrote about Sabine Hossenfelder’s Forbes article and along the way defended it against accusations that it was “sloppy journalism” and representative “the frenzied sensation-driven nature of mainstream publishing” mostly by linking to it, quoting it, and being incredulous at those descriptions. Some have disagreed with that assessment:

First of all let me sympathize: it is mortifying to see your research in print in a way that sensationalizes it.

Next, let me point out that this is not even close to yellow journalism. I know yellow journalism, and Forbes, senator, is no yellow journalism.1

So maybe it’s because I’ve seen a lot worse and I’ve written for popular outlets and my student Kimberly Cartier wrote a thesis about science communication that I’ve become inured to the way that headlines beg for clicks, even if they don’t represent the meat of the article well.

But I think in this case the Forbes article is actually not in that camp. With the benefit of hindsight or insider knowledge, it might look overblown, but consider:

  1. At the time it was written, there was no LIGO response to go on.
  2. Hossenfelder contacted LIGO and they had no formal response—and said they planned none!
  3. Hossenfelder then got a third party to comment, and they found “the results “quite disturbing” and hope[d] that the collaboration will take the criticism of the Danes to heart. ‘Until LIGO will provide clear scientific (!) explanation why these findings are wrong, I would say the result of the paper to some extent invalidates the reliability of the LIGO discovery.’”
  4. We all know that the scientific literature is often understated, especially when suggesting someone is wrong. An abstract that concludes “A clear distinction between signal and noise therefore remains to be established in order to determine the contribution of gravitational waves to the detected signals.” has a pretty clear meaning: the GW detections are in jeopardy.
  5. After all, the strongest signal was 5.1-sigma.  If there is any reason to think the noise is underestimated then the signal drops below the 5-sigma level.  Now I appreciate that the difference between “significant” and “not significant” is not Itself statistically significant,” but the “New York Times threshold” is actually the one place where which side of 5-sigma you are on absolutely matters!

Given all these items, I think the headline and fInal introductory sentence of the Forbes article is fine:

Was It All Just Noise? Independent Analysis Casts Doubt On LIGO’s Detections

…But what if there wasn’t a signal at all, but rather patterns and correlations in the noise that fooled us into believing we were seeing something that wasn’t real? A group of Danish researchers just submitted a paper arguing that the celebration might have been premature.

Especially given the 5.1 sigma issue, I think that’s totally fair. The paper did cast doubt, none of Hossenfelder’s followup investigations dispelled that doubt, and “celebration might have been premature” is an accurate description of the implications if the detection was actually only, say 2.5-sigma (and Creswell et al. implied it could be much lower than that, IMO).

Anyway, YMMV on this. We can agree that it would be nice if popular journalism were as sober as The New Yorker and as popular as cat memes, but I think we can also agree that that will not happen.

The only practical solutions I see to the larger problem are:

  • Get scientists better at science communication.
  • Appreciate those that are good at it and see them and the work they do as an important part of our profession (the aforementioned Kimberly Cartier included a chapter on this as part of her PhD thesis in Astronomy & Astrophysics—I hope in the future this will not seem novel).
  • Make sure that when our work pops up in the media we know how to manage it. Especially a large, high-profile project like LIGO should have1 team members (or access to professionals) that know how to quickly manage stories.

After all, if LIGO had told Hossenfelder that it was planning a response that completely addressed the Creswell et al. paper and showed it was based entirely on poor analysis, her article would have had a different conclusion and different tone (if it had been written at all!). They had an opportunity to get in front of it and shape the Forbes article, but they did not.

But it all turned out OK: their eventual (though unofficial) response is solid and succeeded because they put it on Sean Carrol’s popular and respected blog instead of waiting for the peer review process. Now the story can be “nothing to see here, move along” and, as a bonus, the referee of the Creswell et al. paper has a great template for their review. Double bonus: now the world understands LIGO better!

1For the kids: Bentsen-Quayle.

[Edit: Hannam responds (click to expand):


1I don’t mean to imply LIGO doesn’t have such people—on the contrary I mean that the (by all accounts very good) people it has are essential.

Outreach and Response

What good are blogs?

The LIGO collaboration recently made headlines, made an epoch, and earned itself an all-but-certain Nobel Prize, for the detection of gravitational waves.

Recently, an unrefereed paper appeared on the arXiv questioning the strength of the detections. In brief, LIGO uses two detectors separated by 2,000 miles to filter out noise by looking for coincident signals: real gravitational waves will affect both sites equally, but local sources of vibration should be uncorrelated between the sites.  The Danish authors, who include a scientist name Andrew Jackson, took some public LIGO data of the detection, did some analysis of it, and found that the noise appeared to be correlated between the two sites.  At the very least, they argue, this means that the LIGO collaboration has overestimated the strength of their signal.

It’s a provocative claim: that a major milestone in physics could be a mistake, revealed by a relatively straightforward analysis that any physicist could understand. When I heard about it, I thought “that’s probably wrong, but I’m curious why it is that the sites have correlated noise and how the LIGO team deals with that.”

Sabine Hossenfelder is a theoretical physicist, blogger, and freelance science journalist. She apparently had similar thoughts to mine, and used them as the basis for a column in Forbes on the topic. It’s a nice piece of science popularization, that explains the issue in an accessible way.  She, very responsibly, went to the LIGO team for a response:

Jackson is no unknown to the LIGO collaboration. Upon my inquiry with a member of the LIGO collaboration what to make of the paper, I got the annoyed reply that the collaboration’s management recommends to “respectfully respond that we have talked at some length with the group in the past and do not agree on the methods being used and thus with the conclusions.” Another let me know that a response is not planned.

She also walks the reader through some of the problems with the claim.  I found the column illuminating, but wished I had a better explanation of the issue. I was intrigued!  Hossenfelder concludes:

Making sense of somebody else’s data is tricky, as I can confirm from my own experience. Therefore, I think it is likely the Danish group made a mistake. Nevertheless, I would like to see a clear-cut explanation and “they did something wrong” is too vague for my comfort. This is a Nobel-worthy discovery and much is at stake. Even the smallest doubt that something is at odds should be erased.

Right! But even beyond the issue of how if they want their Nobel they should make sure there is no doubt, there’s also a general outreach angle: gravitational waves are a very popular topic, and this paper, however annoying, had the effect of raising interest in a particular aspect of the science. This paper provided the LIGO collaboration with an opportunity to cash in on that level of interest and explain this particular aspect of the science.

And they did. A member of the collaboration, with the blessing of the collaboration, wrote a guest post on Sean Carroll’s popular blog.  It was just what I hoped to read: an accessible (to me, anyway) discussion of why the Danish group’s analysis is almost certainly wrong and naive, along with a quick tutorial on how LIGO makes sure it doesn’t make similar mistakes.

The whole thing to me was a good example of how various levels of science communication can work: the arXiv (for better or for worse) provided a formal forum for a team to make a scientific claim of high visibility before peer review; the science column provided a way for a professional scientist to engage the public in the issue; the science blog provided a way for the team to make an informal but quick and almost definitive response to what was apparently a straightforward mistake by the Danish group (thus illustrating why one shouldn’t make provocative, unrefereed claims on the arXiv: you’ll usually end up being very publicly wrong).

Then there was a blog post by Mark Hannam on the whole episode.  Now, I get that the LIGO team is understandably frustrated by this sort of high profile sniping by a team that apparently didn’t know what they are doing, and annoyed that they have to spend time putting out these PR fires. The mature response is to turn it into a teaching moment, and they did with the Carroll guest blog post. Now the broader community understands better, the Danish team’s mistake is laid bare, and everyone knows more physics than they did before.

But Hannam doesn’t reserve his fire for the Danish group.  He actually says the thing that annoys him most about the whole thing is Hossenfelder writing it up in Forbes! He refers to her “sloppy journalism” and “the frenzied sensation-driven nature of mainstream publishing”. Did he read the same article the rest of us did?  Take a look for yourself.

Hannam is annoyed that the “controversy” played out it real time and not at the pace of peer reviewed paper. I expressed my eye-rolling at Hannam’s post on Twitter, and got some pushback, mostly because in the confines of 140 characters it looked like I was attacking the LIGO collaboration. It went over to Facebook, and a lot of people disagreed with me.  Some excerpts of rebuttals:

“the methods used for the discovery have been laid out in excruciating detail”

Well, yes, but saying that interested people could figure out the problem by reading your papers is terrible popular science communication; it’s much faster and more efficient for someone to take some time to explain it to everyone briefly than to expect everyone else to take a couple of days to digest the papers and figure out for themselves what the Danish team did wrong.

Of course, you don’t have to communicate your science well in general, but it’s sort of an obligation when your project is on the front page of the New York Times and in the running for a Nobel.

“Younger scientists may think it is cool to have open discussion with non-peer-reviewed arxiv-postings but that’s busy work that takes away from more important analysis and when I was a student/postdoc that’s what conferences were for”

The quick answer is that blogs are cheaper, more far-reaching, and faster than conferences, so why prefer conferences for this particular item?  And it is only “busy work that takes away from more important analysis” if you think communicating your science is not important. If you think it’s part of your job, then you know you have to do it anyway, so it makes sense to focus your efforts on items that already have the public’s attention, like the Danish team’s paper.

Ok, let’s consider an analogy. Recently, we did a press release for a paper that got picked up by a few people, and there were several articles, some with open online comments. And some of those comments (trying to think of a non-“scornful” way to say this) strongly disagreed with our work while exhibiting a lack of familiarity with the subject. Would Jason Wright and James Guillochon suggest that I “missed a teaching opportunity” by not engaging with the comments?

Well, yes, obviously, but not a very big one. Responding to every comment on every article is obviously inefficient and doesn’t scale. But when the whole world is watching your team and your results are influencing in billion-dollar space missions decisions and a Nobel Prize hangs in the balance, it doesn’t seem unreasonable to have some kind of public response to news stories on an accusation from your colleagues that you’ve made a huge mistake.

This is actually a great argument for science blogs: it’s a way to quickly, very publicly make an arbitrarily-detailed response to things like an unrefereed arXiv post. They let you balance the time you put into the response to the claim you’re responding to.

For instance, instead of putting out fires as they come up on Twitter and Facebook as a result of my off-the-cuff tweet, I can have a blanket response to all of them in one big post I can link to.  It’s the same reason that people hold press conferences instead of answering phone calls from reporters all day (but on a much smaller scale, of course).

As I said, if I were the LIGO team I would be annoyed by the episode, but the things that would annoy me the least are that the world showed an intense interest in my work, that I had to explain my science to that interested audience, and that I got to show up a gadfly on a big stage.

[Edit: More responses and details in my next post]

[Edit: Hannam responds (click to expand):



Who Should Be an Author on a Paper? V: Some Errata

It looks like my post was based on the old AAS Ethics Statement, not the more recent Code of Ethics.  That’s fine, but it means the language I quoted was not the latest.  The language on who should be an author is the same, so the heart of my posts are unchanged.

But now, the Code says:

As stated in the National Academy of Science document On Being a Scientist, “The list of authors establishes accountability as well as credit,” and “an author who is willing to take credit for a paper must also bear responsibility for its errors or explain why he or she had no professional responsibility for the material in question.”

So this directly addresses one of the most common objections I’m getting (which is not really an objection to my proposal per se, as I’ve said).  Right there, in black and white, it says that authors may: “explain why he or she had no professional responsibility for the material in question.”

So this part of my proposal really isn’t very radial at all; it’s right there in the new Code of Ethics!

Also present is this new bit:

Data provided by others must be cited appropriately, even if obtained from a public database.

Which I think everyone agrees on.  My entire premise was “what if there is no appropriate citation?” and I’m asking “what does appropriate mean?” I argue that if there is nothing to cite that “counts” today, then this clause can’t be followed, so it no longer overrides the earlier co-authorship requirement.

Finally, on the obligations of co-authors it says:

Every coauthor has an obligation to review a manuscript before its submission, and every coauthor should have the opportunity to do so.

Which is a stronger statement than was in the old policy, but doesn’t affect my argument at all.

The other strain of reaction I’ve gotten is suggestions for reforming our citation and credit system, including adding levels of contributions to papers below “authorship.”  I’m all for that; my proposal had to do with what to do with the system we have in the meantime.


Who Should Be an Author on a Paper? IV: Practical Ethics of Authorship

Part I is here.  You’ll need to read it and prior entries for context.

Let me start this final(?) part with a formal statement of my suggestion:

In general, researchers writing a paper that uses unpublished or otherwise unciteable data they did not produce should invite the proposers/observers/producers of that data to be co-authors.

Now, there are many situations where following my co-authorship suggestion isn’t practical. Maybe there are not well defined “proposers”. Maybe the data are 30 years old and widely used. Maybe there is a timeliness or competitive issue that precludes letting the proposer know what you’re working on. Maybe the proposing team didn’t actually do a lot of work to make the observations happen. Maybe the proposer is a social pariah or one of your more important co-authors refuses to be on a paper with them. Maybe you’re on a deadline and simply don’t have time. Maybe you’re in a collaboration whose authorship rules preclude adding these people to the paper. Depending on the specifics of a situation, those might be part of completely legitimate reasons to go ahead and publish without them.

Ethics is often a case-by-case subject; broadly written rules can become outdated, or fail to anticipate pathological cases, or obviously fail in corner cases, or just be too vague to apply to edge cases.  Personal ethics also come into play: we do not all share the same values, and do not all take the same approach to collaboration. Ethics also depend on expectations of the community, and those can change.

But I think our community’s expectation and standard that we never need to include the people who took otherwise unciteable data as co-authors is wrong and should change. 

I encourage my colleagues to consider adopting a presumption that the observers/proposers of public but unpublished data should be invited as co-authors, and even taken on as collaborators early in the project. If there are good reasons not to do so, that’s fine, but those reasons should be articulated and considered and weighed against the good reasons to the contrary before a decision is made.

So before rejecting this presumption, astronomers should ask themselves:

  • Why not include them?
  • What does it really cost me to include them?
  • Why not gain a collaborator?  Why not have a longer author list?
  • What would I want them to do if the roles were reversed?

In many cases, the answers to these questions might lead authors to conclude that the producers of the data should not be co-authors, and that’s fine.

But let’s ask these questions more often.

Finally, because Josh Peek got me off on this tangent on Twitter, inspired my particular example, and is working on the MAST data policy which will guide this sort of thing, let me suggest a concrete policy for MAST, consistent with my proposal and the AAS Ethics Policy:

  1. Propriety only concerns who can see and use data. It is silent on the issues of authorship. Public data are in the public domain and anyone may download them and use them as they see fit.
  2. STScI will provide guidance to users of its data products on how to properly credit STScI and its employees for their work. This is probably something like: include the boilerplate acknowledgement, and cite such and such papers describing the instrument and analysis methods.
  3. STScI should have an internal policy for how its many scientists accrue credit (citations and authorship) for their work on projects that produce data, especially for papers produced with public data they enabled. This policy should be consistent with community norms and (hopefully) the AAS Ethics Policy (which may need to change).

That’s it!  If authors want to scoop others and not give them co-authorship, that’s not MAST’s problem (indeed, it is part of MAST’s charter to enable such scooping!).  The AAS Committee on Ethics may be interested in that author list, of course, but I see no reason (or mechanism!) for MAST to be telling its users what they can do with public domain data except publish publish publish.

OK, that’s it.  Flame on!  I will probably update this thread with more entries as good ideas roll in.

[Edit: One more post!  I linked to the old Code of Ethics.  The new one actually further supports my position, I think.]

Who Should Be an Author on a Paper? III: A Proposal

In Part I I suggested a modest apparently radical proposal. In Part II I laid the groundwork for defending it. Now, let the games begin.

To recap my concrete example, Joe and his team took public data from the HST archive as soon as they landed (this is public DDT time) and have written a paper with it.  The proposing team includes PI Candice and departed members Amber and Brie, and Candice has also written (but not submitted) a paper on the data. Should Candice offer Amber and Brie authorship on her paper (yes, I think we all agree). Should Joe offer the proposing team members Amber, and Brie authorship on his paper?

I say “yes,” because they contributed to Joe’s paper just as much as to Candice’s! The whole proposing team should be offered co-authorship. This is not current practice.

The easiest way to defend my proposal is by responding to some objections I saw when I proposed this on Twitter. I won’t link to individual tweets because I’ve rephrased some of these to be easier to rebut (hey, it’s my blog!)

But the data are public!  That means I can use the data however I want and I don’t have to include the proposers.
Also: That’s what proprietary periods are for! Once it’s over I no longer owe the proposers co-authorship.

No, data propriety only has to do with who is allowed to look at and use the data. Once the data are public, anyone can look at the data, work on the data, and publish the data. 

But that does not absolve them from their duty to properly acknowledge and credit the producers of the data. This is obvious when the data are already published. Of course you cite the origin of data you use in a paper. So ask yourself: why does the lack of a paper to cite make the procurers of the data any less responsible for their production, or you any less responsible for acknowledging that contribution in a way they get credit for?

But if they never publish their data, that’s effectively an infinite proprietary period.

Again, no: you can use and publish the data. That’s a completely separate issue from whether you have to give credit where it is due.

Why should I give co-authorship to someone that didn’t work on the paper?

Because they effectively did work on the paper as soon as you used their data in it. Since you are using their work you have to give them credit they can use.

But I list the PI’s name and the proposal number in the acknowledgements. That’s credit!

It is credit in a literal sense, but not in any sense relevant to the ethical issue here. ADS will not track it, it won’t appear on their CV or h-index, etc. It would be nice if we had a better way to track this kind of credit than these ways, and I would be very open to an overhaul of how academics give and receive credit.  But until then we need to act ethically in the environment we do live in.

If they wanted co-authorship they should have published sooner.  The fear of getting scooped is what keeps us productive. This would provide a perverse incentive to collect data and never publish it.

These are not ethical arguments. They boil down to: “their sloth justifies my theft.”

But taking on potentially hostile co-authors is not a good idea. Forced collaboration is a terrible idea.

I absolutely agree!

(And let’s put aside the question of why this person would be hostile towards you, and how you’re sure you’re in the right.  After all, as I discussed in Part I, being allowed to do something doesn’t mean you’re not being a jerk for doing it. But let’s assume arguendo you’re in the clear and they’re hostile for some other reason than your misbehavior.)

Here’s what I think the radical part of my suggestion is based on:

co-authorship does not have to mean collaboration

The minimal rights of co-authors are actually set out in the AAS Ethics statement:

All collaborators share responsibility for any paper they coauthor, and every coauthor should have the opportunity to review a manuscript before its submission. It is the responsibility of the first author to ensure these.…All authors are responsible for providing prompt corrections or retractions if errors are found in published works with the first author bearing primary responsibility.

See? No real collaboration beyond the opportunity to review a manuscript. If Candice, Amber, or Brie (all of whom have been offered co-authorship) make demands on the paper that Joe’s team disagrees with, Joe has every right to say “no” and the proposers have every right to stay off of the paper.

But that’s not really a choice. If these teams don’t want to collaborate, then the proposing team shouldn’t be on a paper where they did not get a say in the methods and conclusions. They might even disagree with the conclusions! And if they make a principled stand and decline to be on a paper they disagree with, they don’t get the credit they deserve.

This is true, but this is not a problem with my proposal: it’s a problem with the concept of co-authorship in general, and it comes up all the time. Many co-authors do not agree with papers or in some cases do not even read papers they are on. Regardless of how severe a problem you think this is with our current model, it is not an excuse to keep proposing teams off of your paper.

But it’s also not a general solution: ethically people must refuse authorship if they disagree with a paper. As co-authors they would be “responsible” for it, after all.

Because this is a general problem, and not an objection to my proposal per se, I offer my general solution: I favor requesting that every author provide a one-sentence description of their contribution to the paper. If an author is only on the paper because they took the data, they should state exactly that.

So if an author disagrees with the content of the paper they can add that in, too (it would be reasonable to limit such qualifications to, say, 140 characters in most cases; a bit more if necessary). That way everyone’s contribution and responsibility for the result is clear and unambiguous, and credit lands where it is due. I have done this several times, even though there were no contentious issues to hash out.  In this way authors can state exactly what their responsibility for a paper is, if they like.

I still think it’s wrong to bring on co-authors from competing teams that didn’t even contribute to the text of a paper!

I don’t think this is really at the emotional core of objections to my proposal.

Many of us have had to deal with that that one senior team member that totally slacked off and didn’t even send in comments and may not have even read the manuscript. They probably don’t really deserve to be a co-author, but we still include them with little more than a tinge of annoyance because that’s the community norm: you invited them on at the beginning, and you should presume that they read the manuscript and were happy with it and had nothing to add, and it would be rude and awkward to take them off. Yes, sticklers should insist will that they contribute or take their name off, but this situation does not arouse the sort of reflexive opposition that my proposal does.

Whereas the thought of adding members of a competing team as similarly “silent” co-authors makes us uncomfortable, even tough they unequivocally contributed much more than the slacker to the science and an equal amount to the manuscript.

Why do we feel so differently about these situations? Not because the proposing team is less deserving of authorship than the slacker, clearly. It’s partly because they are “the competition” perhaps, but mostly, I think, because it’s the community norm that we don’t invite strangers onto our papers.

I assert that this norm is unethical and we should change it.

In the next part: some practical issues and final thoughts, including a skeleton data policy proposal for MAST (for Josh).

Who Should Be an Author on a Paper? II: Credit as Currency

In Part I I argued that if you use other peoples’ data in your own paper, you should offer them co-authorship on your paper.  In this part, let me make flesh out the theory behind my proposal, in particular why the policy exists, so that we can apply it where appropriate.

I had a math professor in college who made an analogy that has stuck with my all my career: the product of the Academy is ideas and research output and the currency we use to trade in this product is credit.  We cite, we co-author, we acknowledge. This is at the heart of the AAS Ethics Statement’s rule: if someone did work that made your paper possible, you pay them back with credit in the form of a co-authorship.

Now, the policy is clearly too broad. Sometimes the appropriate currency is a citation, not co-authorship.  In particular, if data have already been published then the norm in our profession is that you don’t need to include them as a co-author; you can just cite the publication.

In many cases, successful proposals are citable and appear on ADS. This provides another way to give credit for using other people’s data, although it is imperfect because proposals are rarely cited, so it’s not really a good way to accrue credit. It’s not a currency that is generally recognized by, say, promotion and tenure committees. If we could change that (make the citations worth more and make them common) it would solve the problem, but that seems more radical to me than my proposal.

Also, the AAS Policy does not define its scope. Which enablers of science deserve authorship?  The AAS guidelines are no help here.  What about the armies of PhD astronomers at STScI and IPAC that enable and reduce NASA space telescope data? The engineers who built the telescopes? The telescope operators? The staff that cleans the dorm rooms at the observatories?

There are professional norms here, but it’s surprisingly hard to articulate them. Note that I’m not defending those norms, just trying to figure out exactly what they are.

Going back to the currency analogy helps a bit here: in the norms of our profession, who needs and appreciates citations and co-authorship as professional currency that advances their careers? Not the cleaning and cooking staff at the dormitories. Many telescope operators do not, but many telescope staff astronomers do.  Many people who write data pipelines and archiving software do.  Certainly instrument designers and builders to, as do some members of the shops that construct the instruments. An imperfect shorthand for this might be “anyone eligible for membership in the AAS” (or their country’s equivalent).

Here I think there is an ethical obligation on observatories and science centers that produce data to offer guidance to users on how their staff that accrues and values citations to get them. This means that data pipelines and instruments need to have papers that can be cited, and staff astronomers that assist with observations in any way need a clear path to getting credit for the science they enable. These centers also need to communicate with their users about what these policies are and what appropriate citation and authorship practices for their employees entail.

OK, having laid the groundwork here, in Part III I’ll defend my proposal from Part I.

Who Should Be an Author on a Paper? I: AAS Ethics policy

I started a really long Twitter conversation by blurting out a radical-sounding assertion that I’ve been mulling over privately for a long time.  This series of posts is an attempt to justify my (apparently) rather unpopular position.

The AAS Ethics Policy States:

All persons who have made significant contributions to a work intended for publication should be offered the opportunity to be listed as authors. This includes all those who have contributed significantly to the inception, design, execution, or interpretation of the research to be reported.

Sounds reasonable! But—like a lot of ethical maxims—this apparently banal statement can be tricky to apply in practice. I actually like this rule a lot and think it should stand with only minor clarifications, but I assert that it is strongly inconsistent with the norms of our profession.  We could change the norms, or we could change the policy.  I think a compromise is in order.

Let’s look at a concrete example:

Consider a team of researchers that proposes for some Hubble Space Telescope time. After submitting the proposal but before analysis of the data begin, two of the co-I team members (let’s call them Amber and Brie) that worked hard on the proposal leave the group. Amber gets a job in industry, and Brie gets a faculty job elsewhere and has no time to work on the project any longer.

The PI (let’s call her Candice) and the rest of the team get the data and write a paper. Do they have an ethical obligation to include Amber and Brie on the paper? I think it’s clear that they do: they clearly “contributed significantly to the inception [and] design…of the research to be reported.”

OK, that’s an easy one. Now let’s make a minor tweak.  Let’s say this was a DDT proposal. That means that the data have no proprietary period, and go public as soon as they are ready. Simultaneous to the above events, another team (led by Joe) downloads the very interesting and useful data, analyzes it, and prepares their own paper.  Is Joe ethically obliged to offer Amber and Brie co-authorship on the paper?

Our professional norms say “no”: this is a different team using public data; why should Amber and Brie be involved?

But our professional society apparently says “yes”: by the book, this situation is no different than the first one.  Amber and Brie “contributed significantly to the inception [and] design…of the research to be reported.” Full stop. By this rule, the entire proposal team should be on Joe’s paper!

In fact, the AAS policy has things exactly backwards of our professional norms: many astronomers would, I think, consider Joe a bit of a jerk for scooping Candice. Even though he’s allowed by NASA to publish the data, there is a general etiquette that we don’t do that, or at least that we ask first, or at the very least an understanding that Candice is perfectly justified being upset about it. But there is also a broad consensus that Joe doesn’t owe Candice co-authorship.

So the AAS Policy is clearly out of step with our norms. Should we change the policy?

I actually think not. I agree that Joe’s act is poor form, but allowed; my (apparently radical) proposal is that Joe should seriously consider inviting Amber, Brie, Candice, and the entire proposing team to be co-authors on his team’s paper.

In Part II I’ll flesh this out.


There is zero evidence for ancient aliens in the Solar System.

OK, now that that’s out of the way…

Sooooo, I wrote a paper and it’s been accepted to the International Journal of Astrobiology. Yay!  Astrobiology refused to have it refereed, claiming it was out of scope, which I admit made me grumpy:

But that’s fine; if they don’t want solar system artifact SETI in their journal, that’s their loss. Perhaps they’ll come around as Breakthrough Listen starts its survey of Solar System objects for radio emission. Anyway, that’s all water under the bridge now.

Normally I would have done a big roll out, a 10-part slow blog of the whole saga, and describe the paper in detail but…

  • I was traveling from California to the Astrobiology Science Conference near Phoenix when I learned it was accepted, so I didn’t have time to blog it.
  • I wanted to get the preprint out right away, during AbSciCon, since it’s my first astrobiology paper, and I thought having it hit the arXiv during the conference would make for good conversations. Also, Breakthrough Discuss had just finished, so SETI was also on people’s minds.
  • A major family emergency had just struck (everyone’s fine now), and I had no time to blog, or even do much of anything at AbSciCon (I have a long draft of a blog post almost ready to go that I haven’t had time to even look at in two weeks).
  • I think the paper is very short and readable—an easy register, not too much jargon—so if you’re interested in what’s in it I recommend you just read it.  My blog would just quote from it, for the most part, anyway.
  • I thought I’d do a slow-blog later—I wasn’t really expecting much in the way of press to scoop me; it’s kind of a fluffy paper (to use Steinn’s term for it)
  • That said, I had shown the paper to the great folks at the Atlantic science desk (Ross Andersen asked what I had tweeted about above) and so I knew it would be treated well if it got any press at all.

Well, it certainly got some press! Not #TabbysStar #AlienMegastructures levels of press, but enough that I have a very busy week!

The Atlantic article was nice, and if that had been the main source of news stories, I think it allwould have gone much better.  But somehow, the yellow press found the paper on their own on the arXiv (do they read astro-ph daily?!) and ran away with it without asking me what it was about. The Daily Mail, that British rag of a tabloid, claimed that I “believe[] the aliens either lived on Earth, Venus or Mars billions of years ago.”

Wow. Things went downhill from there as the NY Post, repeated the article, and USA Today posted a video that was even worse. The only saving grace is that according to the worst of the articles, the irresponsible astronomer posting Ancient Aliens papers on the arXiv wasn’t me:

Gizmodo got to talk to me after the craziness began, and they were great and helping me to reframe things more appropriately.  Universe Today was really careful to get things right, too, as was NBC Mach.

For the record, the premise of my paper is the fact that we have no evidence for any prior technological species in the Solar System. My paper asks, is this a dispositive null result? That is, has our paleontology on Earth and mapping of the larger Solar System bodies basically proven that we are the first such species around?  After all, the idea that we are not is very old (read the paper—the earliest citation I got from folks contributing to my Twitter research was 1900 years ago!).  This was actually an area of active discussion in astronomy until the advent of robotic exploration showed no canals on Mars, no ruins of cities on Venus.

But is it too soon to rule out the possibility entirely? I thought the idea needed to be formalized, to have a name, because it seemed to me the literature had forgotten about it prematurely. Papers on searches for alien artifacts in the Solar System always seem to implicitly assume such artifacts would have come from an interstellar species—but if Venus was ever inhabited, couldn’t its inhabitants have something to find?

So, I ask, what’s left?  Ancient things are hard to find, because planetary surfaces erode and subduct things away. We have a pretty good understanding of life on Earth, and the window between “so old we wouldn’t know about it” and “so recent we couldn’t have missed it” might be very narrow. But is it really closed?

I don’t know, but it seems like the kind of question we have the ability to answer today. Someone should answer it! How long would free-floating artifacts in the Solar System last? How far beneath the surface of Mars would technology have to be to survive billions of years? And how deep can we probe with radar? How long ago could Mars have been inhabited?  Venus How wide is the window between technology we could never discover because it has been too long, and technology we know isn’t there because we’ve checked?

That’s the conversation I wanted to have.  That’s why I wrote a paper on Prior Indigenous Technological Species: not because I think they exist, but because we’re at the point where it should be possible to say for sure that certain types of them didn’t. The end of the paper is all about the things we can do to start drawing some conclusions.

And that’s a neat SETI (SPITS?) project someone should undertake.

At least I think it’s neat.  Your mileage may vary. In that vein, let me use this as an opportunity to address a weird misconception that the SETI grumps in astronomy have. Apparently, the only reason to do artifact SETI (or even mention it in a paper on another topic) is to get attention. Seriously, I’ve had good astronomers I respect make this claim and defend it when challenged. It’s a real attitude out there.

Well, the truth is exactly the opposite. When trying to do artifact SETI, I have inevitably caught all the wrong kind of attention from the yellow press and the ufologists.

And it is mortifying.

So why do I carry on? Certainly not for the attention. I carry on because it’s interesting, and because lots of other colleagues I respect tell me they find it fascinating and worth working on.

Now, I’m not claiming to be some sort of martyr for the cause, here. My point is that it’s a problem worth working on despite the attention, not because of it, and so the SETI grumps that think otherwise should seriously reconsider their assessment of the motives of SETI researchers.

Now excuse me while I answer all these emails from Coast to Coast and ufologists sending me pictures of clouds.


Ethics of Minor Rules

Following up on the ethics in basketball thing:

I was arguing with my neighbor about the poor aesthetics of a sport where breaking certain rules is encouraged and accepted (as I wrote, I think basketball is broken), and he argued that there aren’t any “rules” in sports, really, just tradeoffs: if the penalty is worth it (or the whole point of it) it’s not unethical to break the rule, it’s just part of the game.

The “don’t intentionally foul” article helped crystalize this for me. There, Lopez argues that there are regulatory rules and “constitutive” rules: that the latter define the sport, and the former are essentially arbitrary details specific to a particular variety of the game (pro vs. collegiate, pickup vs. formal, etc.)  I had sort of a similar feeling, but my argument last time helped define things better for me.

The constitutive-regulatory spectrum has no sharp boundary: enough regulatory rules and at some point it’s a new game (witness rugby, soccer, and the many versions of football; all of them evolved from the same sport).  The real distinction for ethical purposes is which rules the community expects to be followed—what’s “normal”.

Consider an analogy to law. Is it unethical to break the law? Remove for a moment the situational dependence involved in, say, civil disobedience or justified homocide, and just consider breaking a law because you want to or it’s convenient. In this case, it depends on how society views the law.

For instance, if it’s the middle of the night and there is zero traffic, is it ethical to jaywalk, or should you dutifully go to the corner and push the walk button and wait for the light? Clearly, jaywalking is no big deal; the ethical consequences of jaywalking in that situation are probably not worth the thought given to the problem in the first place.

If the law is that the speed limit is 65 and you’re doing 67, this is not a big deal and generally not unethical, per se.  If you’re doing 65 and you’re still the slowest one on the road (it happens!) there is a good argument that you should speed up.

Don’t buy it? Look at how outraged (and actually dangerous) people became when some students pranked a highway by driving the speed limit, in formation:

This is not the cleanest example—the law says you should leave the passing lane clear for faster traffic to move ahead—but it more than illustrates what every driver knows: the speed limit is not a hard limit, and no one expects it to be universally honored. Murder, of course, sits at another end of the spectrum, because laws against arbitrarily killing people are pretty fundamental to the functioning of society; jaywalking is more of an arbitrary detail that can often be ignored.

Back to sports: I think “constitutive” rules in sports aren’t more important because they’re foundational per se, but because being foundational they’re less likely to have a consensus that it’s OK to break them. The “Mano de Dios” soccer goal is notorious because the rule that was broken—don’t use your hands in soccer—is foundational (“constitutive”), which makes the violation seem especially flagrant. Compare this to the equally legendary 1999 World Cup shootout:

The US won in part because the US keeper, Scurry, left her line before the ball was kicked, which is a technical infraction (go to 0:43, and compare Scurry’s jump on the kick to the action of Chinese keeper, Gao, holding her line until the moment of the kick at 1:00).  This isn’t to minimize or question the validity of the US victory: this technical infraction is so minor and violated so routinely that even most soccer fans aren’t even aware it exists.  My point is that the difference in reaction to these two goals shows that Lopez’s “constitutive” vs. regulatory continuum maps pretty well to my “community norms” test.  And the latter is better connected to ethical reasoning.

Why is socially acceptable (even expected) to break some rules and not others outside of sports? That’s a deep topic, but my point isn’t to explain why, just to show that it clearly is, because it’s a key element in any ethical analysis of when it’s OK to break a rule, whether it’s a speed limit or a basketball foul or a high crime or misdemeanor. It’s not a dispositive test (society can condone evil law-breaking behavior, like lynching) but I think it’s the difference between my conclusion and Lopez’s.

Ethics in Baskeball

According to this Ask the Ethicist column, it’s unethical to follow a basketball coach’s order to strategically, intentionally foul?!

This is a neat, regular column written by Rock Ethics Fellows here at Penn State, and I normally find them instructive, but as a Rock Ethics Fellow myself I find this one to be totally wrong.

You can’t derive specific ethical rules purely from first principles, as this author tries to do. Ethics are normative, and the norms are set by the expectations of the community. That’s what “unwritten rules” are all about!  It is widely accepted in basketball that an intentional foul is a legitimate strategy in basketball. This analysis is otherwise good, but it comes to the wrong conclusion because it ignores this essential element of the problem.

Instead, the author here tries to draw a line between constitutive and regulatory rules to come to his conclusion, but this line is arbitrary and subjective, so it leads to a squishy answer. He argues that free-throws, for instance, are not intrinsic to the game of basketball, which would be news to most players! He also appeals to the NCAA’s stated core values (HA!) to argue that intentional fouls violate those values, because strategic fouling is only appropriate when “victory is regarded as the main goal”, but “victory is not mentioned as the main goal of college sports”.  That may be true for the endeavor as a whole (after all, there are just as many winners as losers!), but winning is certainly the main goal of an individual game. By definition! If that’s not in the NCAA rules, it may be because it’s so obvious, so fundamental to the definition of an athletic competition, that it doesn’t need stating.

This is not to say that following community expectations is a defense against immoral behavior—sometimes the community consensus is unethical. But there’s no great social ill in a sport having a too-lenient penalty for purely technical infractions like this (intentional fouls are almost always highly technical infractions, not attempts to injure or be unsportsmanlike).

And it’s true that cheating to win is unethical, especially in college sports where sportsmanship is supposed to be a core value.  But by this argument I could try to say that head fakes are unethical, because I am deceiving my opponent in an attempt to win the game. Of course, head fakes are obviously not unethical, and the reason isn’t that head fakes aren’t disallowed by the rules (lots of forms of cheating aren’t mentioned in the rules!), it’s because they are considered a legitimate strategy, just as intentional fouls are.  That is, the line is between what’s considered “fair play” and what’s not is set by community expectations, and we’re back to the unwritten rules that this author left out of his analysis.

Now, I happen to agree that the rules of basketball are broken, in that if it is regularly to your advantage to break the rules then the penalty for rules-breaking is too light. But that’s an aesthetic concern, not an ethical one.

I can think of lots of concerns that would make it ethical to not try your best to win a game. There are lots of heartwarming stories of athletes refusing victory in the name of good sportsmanship. But a quixotic devotion to avoiding fouls is not one of these higher values—your opponents will feel confused and robbed of a fair victory, not impressed by your ethics.

[Edit: John Gizis points out that the author could be referring not to end-of-game fouls to stop the clock, but to “Hack-a-Shaq” strategies.  In that case, the author is probably right. This strategy is not universally accepted, even in professional basketball, so in collegiate sports (with its higher emphasis on character building and sportsmanship) it is probably outside of community norms.

That said, it’s hard to really distinguish “Hack-a-Shaq” from the intentional walk in baseball.  I wonder if  Francisco Javier Lopez (the author of the ethicist column) would say that’s unethical too?  I presume so, although I think it’s fine (because collegiate baseball players expect it and they think it’s fine).

Second edit: Chris Palma points out that the intentional walk in baseball has a similar ethical ambiguity. A situationally strategic walk (to put someone on first to create a force-out situation when runners are already in scoring position, for instance, or pitching around the 8 spot to get to the pitcher with 2 outs) is, as far as I know, universally accepted strategy, and so (I would argue) not unethical.

But used as the baseball equivalent of “Hack-a-Shaq”—routinely pitching around dangerous hitters—was somewhat controversial when it happened to Bonds, Sosa, and McGuire. I could imagine that in collegiate sports a similar approach might be considered unsportsmanlike.

So it’s all a matter of degree.  For instance, is a defensive player with a “five fouls to give” mentality playing unethically? After all, anticipating that you’ll play so aggressively that you foul your opponents five times by the end of the game isn’t much different from Hack-a-Shaq in principle. Again, I think you’d have to ask the players and coaches, not try to deduce it from first principles.

Third edit: More here in part II.]

Changes to AAS Governance

The American Astronomical Society is about to change its governance structure for the first time in 50 years in response to a task force report on the topic. Here is the task force chair’s description of the process, and here are the executive officer’s thoughts.

Here is a summary of the changes (from the executive summary):

To improve responsiveness and assure timely action on important matters, and to move toward a model consistent with best practice, we replace the AAS Council with a Board of eleven members that meets monthly. To assure effective communication between this Board and the entities in which our members work to advance the interests of the Society and our profession — our Committees and Divisions — we provide a Board liaison for each. Most importantly, each Committee and Division Chair is scheduled to attend from two to four Board meetings per year in which their issues are pre-ordained agenda items.

To enhance inclusivity in the governance of the Society, Committee members and chairs will no longer be appointed by the Board (nee’ Council); members will be derived from volunteers and selected by the existing committees, and the committee members will, in most cases, elect their own Chairs.

To further involve a broader community in setting the strategic directions of the Society, the AAS Council will be reconstituted as a body — the Strategic Assembly — including the Board and the Committee Chairs of the eleven Standing Committees as well as Division representation. The Assembly will meet twice a year at the Society’s scientific meetings 1) to foster collaboration among committees and with the Board, 2) to improve communication, and 3) to guide the strategic thinking of the Society.

The many changes, large and small, outlined in the attached document have been carefully designed to promote inclusivity, foster communication, embrace creativity, and maximize transparency — in short, to enhance the functioning of the Society so that it will be the welcoming and natural home for the many people who, in a variety of different capacities throughout their careers, work to enhance and share humanity’s scientific understanding of the Universe.

Full details in the task force report.

The AAS would like feedback from its members specific to the drafting of the bylaws to be sent to the task force chair, David Helfand, and general comments can be emailed to AAS President Christine Jones.

Comments can also be sent anonymously here.  Comments will be appreciated before May 12.

There will be a town hall about these governance changes on 7 June at 12:45pm at the summer AAS meeting

Astronomy and “Meta-Astronomy”: An Allegory

My blog is about astronomy and “meta-astronomy.” By the latter I mean the stuff that isn’t strictly astronomy research but is necessary for, or relevant to, its practice. I think both astronomy and meta-astronomy are appropriate topics for journals, talks, conferences, blogs, and research, especially since the line between them is not sharp. Here is an allegory I thought of this morning to illustrate this point.

This story is pure fiction. The allegory is purposeful, but literal similarities to real people, events, and fields of study—while perhaps not entirely coincidental—are not intentional or relevant.

Joe is an exoplanet astronomer at Research Center. Like many exoplanetary astronomers, his PhD thesis was on planetary science, which gave him a firm foundation for studying exoplanets, their composition, internal structure, and their potential habitability.

He goes to an internal departmental lunch talk by Diamond. Diamond is another exoplanet astronomer at Research Center. Like many exoplanetary astronomers, Diamond’s PhD thesis was in stellar astronomy. Her talk is about the complications of deriving exoplanetary properties from observations: starspots, convection models, mixing length assumptions, and photometric errors.

On the way back to his office, Joe and another colleague with a planetary science background, Jack, banter about how it feels to attend these “stars” talks: they agree that they appreciate stellar astronomy is important for their work, and that they should know that stuff better than they do, but they’re glad to get back to their offices so they can focus on their part of the science.

Joe is organizing a conference on exoplanets focusing on exoplanets’ composition, internal structure, and habitability. It’s going to be an important meeting where exciting new results will be presented and discussed for the first time, and he wants the best exoplanet astronomers to attend so it will be maximally successful.

He heads over to Diamond’s office and asks if she will please attend, since she is one of the best exoplanet scientists. She points out that all of the planned sessions titles contain geology jargon, and there don’t seem to be any talks about stars. Perhaps she could recommend some speakers for a panel on that?

Joe explains that the success of the conference will depend on it staying focused on its primary topic, and he doesn’t want to “dilute” the science with “stars stuff.” She points out that “stars stuff” is actually very relevant to exoplanets. Joe hastily agrees, but reemphasizes that he wants *this* conference to stay focused on geophysical aspects of planets. Will she please attend?

Diamond points out that she has limited time and can’t accept every conference invitation. She says it looks like Joe is giving only lip service to the relevance of stellar astronomy to his work, and that his actions indicate he doesn’t really think it’s very important at all. She points out that the “focus” of his conference excludes much of what she spends much of her professional time thinking about. Disappointed, Joe says thanks and goes back to his office.

He is annoyed. He would like to work more closely with Diamond, since they are both exoplanet astronomers in the same department, and they generally get along well, but it seems like she wants to drag stars into every discussion. He wishes she could compartmentalize better.

Diamond is annoyed. Joe professes to want to work with her, but can’t seem to appreciate that stars are integral to her work. She finds many planetary scientists are like that: they seem to imagine that they can divorce planets from the stars they orbit. Of course, that’s true in a purely theoretical, pedantic sense: many planetary interiors are more-or-less insensitive to the most of the precise properties of the star they orbit. But in practice you can’t measure anything about those planets without observing the stars and knowing their properties. She finds Joe’s myopia on this point frustrating.

Back in his office, Joe is glad to be able to get back to work on his geophysics. He looks at his panels: his science organizing committee has done a good job of getting many of the best speakers and presenters, even though many people had to decline.

Diamond looks at the preliminary program of Joe’s conference. All of the panel speakers come from a planetary science background. She finds a single stellar astronomer on the registration list. She thinks about going to Joe’s office to point this out, but she’s had this conversation with him before. He’ll say that he tried to get stellar astronomers to attend—he even tried to get her to attend! But, he’ll say, they all declined, so what does she want him to do?

I hope my astronomer friends will not be like Joe. When a fellow astronomer tells you a subject you find to be “meta” is important to their work and needs to be part of your science, your conference, or your work, accept that, embrace that, and act on that. Don’t nod and then go on treating it as a tangent or a distraction to your work. And when you look at the composition of panels and find homogeneity, don’t let “they all declined” be an excuse. Ask “what is it about my panel that made only certain kinds of scientists end up on it?”

Przybylski’s Star IV: Or…

Part IV of III.  Part I is here.

A coda: Howard Bond correctly points out that my three explanations are only necessary if a very plausible and less interesting explanation is wrong (a caveat that I had in an early draft of my posts but edited out unintentionally.)

The identification of short-lived actinides could be a mistake! The Gopka et al. identification of these lines was made in a journal I had not heard of, Kinematics and Physics of Celestial Bodies, apparently originally in Russian. As far as I can tell, the paper has been cited exactly once, by the Dzuba et al. paper that proposed the metastable heavy isotope.

The journal and language of the Gopka et al. paper aren’t necessarily problems, of course, but they do raise eyebrows. The fact that it has not been cited could mean that the paper was simply not read (not surprising, given the journal), or that everyone who studies the star that saw the paper decided it was not worth citing, even to refute it.

[Edit: Steinn is much better at this than I am.  He points me to a 2003 AAS abstract by Crowley et al. supporting the existence of short-lived isotopes, a topic Howard Bond also mentioned on Facebook to me. Steinn also finds this paper and this one which I think I missed because I didn’t realize that promethium, a lanthanide, has no isotopes with half-lives longer than 20 years.

The Mkrtichian paper I linked to in the last post mentions Bidelman et al. PASPC, 336, 309, as supporting the short-lived isotope interpretation, and conference proceedings by Yushchenko, Gopka, & Goriely that ADS doesn’t know. Goriely discusses mechanisms here.

So the claim is stronger than I originally hedged in this post.  It’s put best in this followup paper by Crowley it al., originally shown to be by Brian Davis (but which I only just found again, now that I’m thinking of Pm): “The spectroscopic evidence is strong enough that we would declare promethium to be present without hesitation, if any of its isotopes were stable.”  In their other words, it’s only the strong prior against finding unstable isotopes that makes them hedge.]

The mystery of Przybylski’s Star is still a very good one if there are no short-lived actinides isotopes in the spectrum—the identification of the stable lanthanides seems quite secure and fascinating and it remains the most peculiar of the peculiar A stars—but it would mean that it is much more plausible that technical but mundane explanations for the star exist.

[P.P.S. There is now a part V/III about prior art by Drake and Shklovskii.]

Przybylski’s Star III: Neutron Stars, Unbinilium, and aliens

Part I is here.

Last time I promised three solutions to the problem of short-lived actinides in the atmosphere of Przybylski’s Star.  Here they are:

1) Neutron Stars

In 2008, shortly after identifying the “impossible” elements in Przybylski’s Star, Gopka et al. proposed a solution: the star has a neutron star companion.  Neutron stars have strong winds of positrons and electrons that bombard the heavy elements in the atmosphere of the star, transmuting them to the elements we see.

The big problem with this is that these are sharp lines, so we can measure radial velocities to Przybylski’s Star, and it does not have a short period neutron star companion.  Which is great, because the last two solutions are even more fun.

2) Flerovium, Unbinilium, Unbihexium

A few days ago I saw this from William Keel on Twitter:

Following his link, I found a delightful proposal for Przybylski’s Star.

Atomic physicists have long sought to fill out the periodic table of the elements.  Since the discovery of Francium in 1939, all additions to the periodic table have come from elements synthesized through nuclear reactions.  Every few years you’ll see a news item about one of the teams around the world that has finally proven that they have produced a tiny, fleeting sample of some heavy element, by detecting its presence before it decays away in seconds (or less!).

There is reason to believe, though, that there might be longer-lived elements higher up the table, in an “island of stability” that experimenters have yet to reach.  This is a region of the Table of the Isotopes that might have unusually stable members because they contain a “magic number” of neutrons and protons.  According to Wikipedia:

Many physicists think [these isotopes’ half-lives] are relatively short, on the order of minutes or days.[2] Some theoretical calculations indicate that their half-lives may be long, on the order of 109 years.[14]

Enter Dzuba, Flambaum, and Webb, who propose that the source of the short-lived actinides in Przybylski’s Star is one of these isotopes! As the isotope decays, its daughter products—all less massive than it but still actinides—are visible in the star before they decay away. There would be some steady-state concentration dictated by the lifetime of the isotope. They propose the parent isotope could be 298Fl, 304Ubn, or 310Ubh.

If this is right then it means that we can discover a new, important isotope the old fashioned way—in nature! It would not be a first element to be found first in a star, though—helium is so named because it was first discovered in the Sun.

But where would it come from?  Dzuba et al. suggest that it might be the product of a supernova explosion, like other neutron-heavy elements. Its half life could be short enough that it would be present in a young A star but very rare on the Earth—or perhaps you need a certain kind of supernova to make it, and one of those wasn’t in the mix that generated the elements that make the Earth.  If so, it could be common in other stars and planets, but just very hard to detect in anything other than an Ap star with levitation.

Very cool!

3) Aliens

The last of the three solutions I’m aware of, whispered but never published, is that it’s the product of artificial nuclear fusion.

Here on Earth, people sometimes propose to dispose of our nuclear waste by throwing it into the Sun (in one case, literally throwing it:)

(This is a terrible idea, by the way. I mean putting nuclear material on top of giant towers filled with rocket fuel and igniting them—but Superman IV too.)

In fact, 7 years before Superman thought of the idea, Whitmire & Wright (not me, I was only 3 in 1980) proposed that alien civilizations might use their stars as depositories for their fissile waste (because of course alien civilizations would use 20th century nuclear technology for their energy needs…but I digress). They even pointed out that the most likely stars we would find such pollution in would be… A stars! (And not just any A stars, late A stars, which is what Przybylski’s Star is). In fact, back in 1966, Sagan and Shklovskii in their book Intelligent Life in the Universe proposed aliens might “salt” their stars with obviously artificial elements to attract attention.

So short lived, obviously artificial elements in A stars are in fact a prediction of artifact SETI!

This just goes to show that artifact SETI is hard. When people stick their necks out and make bold, silly-sounding predictions about unambiguous technosignatures like this (or like megastructures), I suspect they usually don’t actually expect them to come true. And then when they do come true (as in Przybylski’s Star, KIC 12557548, or Boyajian’s Star) not only are their prediction papers rarely cited (which is, I think, inappropriate), but there’s always immediately a flurry of perfectly natural explanations that arrive to explain things without aliens (which is, I think, totally appropriate).

I think the answer to SETI will ultimately come, if it comes at all, from communication SETI because the signals it seeks are pretty unambiguous, but who knows? If that narrow band microwave carrier wave is ever found and we can’t decode it, maybe some plausible natural maser emission source will be hypothesized to explain it away, too?

We should keep trying though, because even when artifact SETI finds no aliens, it finds interesting things. After all, regardless of what the solution to Przybylski’s Star is, it’s bound to be fascinating!

Anyway, that’s the end of this series. I know that Tabby’s Star is supposed to be The Most Mysterious Star in Our Galaxy, but I think Przybylski’s Star gives it a run for its money.

Edit: One more part: a caveat I had meant to include earlier but inadvertently edited out.

Przybylski’s Star II: Abundance Anomalies

Last time we talked about Ap stars in general. Now, let’s get to the really weird part.

In cool stars (hotter than type M), most of the lines by number are from the element iron. This is because of two “accidents”. The first is that due to the rules of quantum mechanics, iron’s six(!) outer (“active”) electrons have a lot of ways they can be excited. In fact, the 3d shell alone has 120 substates that form 25 distinct spectroscopic states, each with its own energy level. The second is that due to the rules of nuclear physics, iron is the end product of runaway fusion in stars, and so gets spewed out in great quantities in supernova explosions. The result is a large number of lines with relatively large strengths. In fact, until Cecilia Payne’s PhD thesis showed otherwise (Best. Thesis. Ever, by the way) this was sometimes taken as evidence that the Sun was mostly iron (it’s mostly hydrogen in fact, no matter what “iron sun guy” tells you.  Stellar astronomers know who I mean.)

We might expect, then, that most of the lines in Ap stars would also be iron, though perhaps of the ionized variety (since they’re too hot for neutral iron).  Not so; in fact for a long time Antoni Przybylski wondered if his eponymous star even had any iron; its abundance is down by a factor of at least an order of magnitude from the Sun’s.

Instead, Przybylski found lots of other elements in his weird star: strontium, lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium… stuff you rarely hear mentioned outside of a Tom Lehrer song.

Now, these things should be only present in the tiniest of abundances, not the most easily seen lines in the atmosphere! What’s going on?

The answer seems to be levitation, although it appears we still don’t have a great model for it.

Here’s the idea, as I roughly understand it: The strong fields, high temperatures, and still atmospheres of Ap stars combine to create a situation where the atoms in the atmosphere, being mostly ionized, get stuck to the field lines and sort themselves out by element. This is because they can only move in one direction, along the field lines, and the strong radiation from the hot star provides a sort of upward force on the atoms, depending on the specifics of how they absorb photons (which depends on how many electrons and protons they have—that is to say, what element they are). I’m fuzzy on the details (I think maybe everyone is), but the bottom line is that the ions of a certain element get concentrated in a thin (or at least high) layer in the atmosphere.  If this layer is high enough, we see it in absorption and the element looks much more abundant than it really is (because we usually assume the atmosphere is well mixed, not stratified). And if this layer is low enough, we might not see the element at all!

So that’s apparently what puts the “p” in “Ap,” the bulk star does not have weird abundances, but its upper atmosphere does because the upper layers of the star are differentiated and stratified!

But that’s not what’s so weird about Przybylski’s star.  No, that star doesn’t just have weird abundance patterns; it has apparently impossible abundance patterns.  In 2008 Gopka et al. reported the identification of short-lived actinides in the spectrum. This means radioactive elements with half-lives of order thousands of years (or in the case of actinim, decades) are in the atmosphere. 

What?! The only way that could be true is if these products of nuclear reactions are being replenished on that timescale, which means… what exactly?  What sorts of nuclear reactions could be going on near the surface of this star?

There are three proposed solutions I’m aware of.  The first is about 8 years old; the second is brand new and a “huge if true” sort of exciting idea. The last is quite fanciful and has never, so far as I can tell, gotten past a journal referee (if anyone’s even tried to publish it), but sort of dials the “huge if true” up to 11.

More on these next time.

Przybylski’s Star I: What’s that?

OK, a new slow blogging.  This one in three parts.

Przybylski’s Star is my favorite astrophysical enigma (this coming from the guy notorious for making Tabby’s Star famous!)  It is occasionally mentioned as a SETI target, but usually in private conversations or irreverent asides on social media. I’m not sure when I first heard about it, but it may have been when looking at the Wikipedia page for stars named after people while doing research for that other star.

Przybylski’s Star is famous for having bizarre abundance patterns.  Not like: “oh look, the carbon-to-oxygen ratio is greater than one”; more like this star has more praseodymium than iron. Yeah.  How could that be?!

First off, let’s start with the basics.  Przybylski’s star is an Ap star.  That’s not “app”, that’s “Ay-Pee”, as in spectral type “A”, with a note “p” meaning “peculiar” (which is an astrophysical understatement.)

Normally, A stars are pretty boring, spectrally.  Cool stars, like the sun, a G star, have convecting envelopes (and atmospheres) like a boiling pot of water; this drives a magnetic dynamo that gives the Sun and other cool stars their magnetic fields. Hot stars (spectral types mid-F and hotter, including A stars) have radiative envelopes, meaning that most of the outer layers are very still, like the water in a bathtub left untouched for days. This means no dynamo.

Apparently, this figure from the Wikipedia page for magnetic braking of stars is supposed to illustrate how it works.

As stars form from collapsing clouds of gas, they spin up, going faster and faster.  When they finally “turn on” they can be spinning so fast they they are near break-up speed: the centrifugal force of the spinning is enough to make them oblate.  Cool stars have magnetic fields, and as the star’s ionized outer atmosphere escapes in a wind, the wind particles get stuck on these field lines and fly down them like beads on a spinning wire.  The fields, being anchored to the star’s surface, impart some of the star’s angular momentum onto the particles, and the star slows down ever so slowly. Over billions of years, the star spins down to rotation speeds of more like once per month.

But hot stars lack this field! As a result, they never spin down. The rapid rotation greatly Doppler broadens the lines: the light from the approaching limb is moving towards us very fast, so its light is blueshifted (just as the receding limb is redshifted). The result is that the “missing colors” that characterize the elements in the star’s atmosphere (the absorption lines) get smeared out a lot.  In fact, the only lines broad enough not to be smeared out beyond recognition are usually the hydrogen lines (the Balmer lines), which are particularly strong in A stars which are hot enough to excite hydrogen but not hot enough to completely ionize it.  (In fact, A stars are so named because in Williamina Fleming’s stellar classification scheme they came first, having the strongest Balmer lines.)

But Ap stars break all the rules.  They have intensely strong magnetic fields, and as a result they don’t rotate fast (presumably having slowed down long ago), and as a result they have very narrow lines, and as a result you can see all of the spectral features of the elements in their atmosphere.  Why?

I’ve never seen a good answer as to why Ap stars have strong fields.  They could be primordial or generated from a dynamo, says Wikipedia, which is fine but misses the weird part: regardless of where the field comes from, why do only a minority of A stars have such fields? What’s different about them?

And here’s the even weirder thing: the abundances of the elements that we get to see thanks to the slow rotation are way off of the abundance patterns we see elsewhere in the universe.  Why?

Next time, I’ll discuss likely answers, and then get to the weirdest member of this already weird class: Przybylski’s Star.

Oh, two last notes before moving on.  First, that name. It’s Polish, and despite what a phonetic Polish pronunciation guide might imply, it’s apparently pronounced “shi-BILL-skee”.1  Not as hard as it looks. (And not as hard as some Polish words are to say. Incidentally, first-exoplanet-discover and Penn State Professor Alexander Wolszczan’s name is pronounced “VOLSH-chan”.  Mentally replace the z’s with h’s and you’ll be fine.)

Secondly, the seminal paper on Przybylski’s star gets fewer citations than it should because, as far as I can tell, Nature misspelled his name!  You can find it here in ADS, but not if you search by author! [Edit: The folks at ADS noticed my Tweet about this, and they have fixed it! It is still wrong on Nature’s website, though.]

1Apparently the initial “P” is not completely silent, but it’s so subtle that to untrained US/UK ears it might as well be. I think it’s roughly approximated by having your lips closed when you start the “sh”: the slight plosive as your lips pop open is all it takes, as in the interjection “pshaw“. It’s not “puh-shi-BILL-skee”. Thanks Andrew Przybylski‏ (@ShuhBillSkee) and Jackie Monkiewicz (@jmonkiew) for setting me straight.

Trump and Fascism

To my friends and followers who disagree with or don’t understand the strong reactions Trump gets from across the political spectrum, I offer this:

After WWII, there emerged a liberal consensus in America that has dominated politics and journalism. By “liberal” I don’t mean “Democratic”, I mean the broader understanding that tolerance of differences among Americans was an essential component of the American fabric. Until recently, even the most conservative Republicans understood that speaking out in explicit contradiction of this consensus was political suicide. When liberals warn of the dangers of “normalizing Trump”, they aren’t just talking about his behavior and tone; they also mean his regular, even gleeful violations of this consensus.

These values were imparted to me and many of my generation (and the next) by my parents’ generation, and onto them by the American reaction to the rise and fall of fascism, especially its most evil and visible manifestation in Europe. Certainly some of this came from the inevitable vilification of our wartime enemies, but it was largely justified by the horrors revealed by the post-war occupation of Germany. Family lore is that my maternal grandfather was one of the officers that led American forces through Germany after VE day, and gave ordinary Germans tours of the concentration camps.

This video has been making the rounds, and I encourage you to watch it with this mindset. It is a propaganda video produced by the US government in 1943 in an attempt to inoculate America against the tactics the Nazis used to take control of Germany. Its parallels to recent events are eerie (so eerie I at first suspected that it was an elaborate hoax, but it appears to be genuine, having been used as part of the effort to desegregate the armed forces.)

Today’s left will find much to fault in the video (it is, after all, almost 75 years old) but I’m not offering it as a guide to how you should think. I’m offering it as a good example for the foundational values that many Americans find violated by Trump, and why the analogies to fascist Europe are not made hyperbolically. Trump’s rhetoric and actions are literally, exactly what we were raised to be on guard against.