Tag Archives: science

Doing SETI Better

One of the reasons SETI is hard is that we don’t know exactly what we are looking for, and part of that difficulty is that we still aren’t sure of who we are.  It seems counter-intuitive, but in order to be good at looking for aliens, we have to become experts at understanding ourselves.

Looking for the unknown

Not knowing what you’re looking for is common to many exciting fields in science.  For instance, another goal of astrobiology is to find biosignatures, but in order to know what those are, we have to make assumptions about how life works, based on life-as-we-know-it.  We must balance the need to define the observations that would constitute a successful detection against the fact that life out there might be as-we-don’t-know-it.

Or dark matter: it could be a common particle or a rare one, it could interact with itself or not, it could reveal itself in gamma rays or something else, it could be one of the hypothesized elementary particles or one we haven’t thought of, or it could even be a modification to the laws of gravity.  The best we can do is guess at its nature and look see if there are detectable observational consequences of that guess.

In the hunt for biosignatures, we can appeal to biology, chemistry, and other fields to follow the chain from the definition of life to observable consequences.  In dark matter detection we can appeal to fundamental physics. What do we have in SETI?

Well, we certainly have physics: there are physical laws we believe are fundamental and that we know pretty well, and we can think about energy use and how it would manifest itself. We also have ourselves: we are a technological species, so we can think about how we would detect a species like us.  This last point is analogous to the hunt for biosignatures: we have to balance the need to define technosignatures of intelligent life as we know it, while keeping in mind that perhaps the only technological life out there is as-we-don’t-know-it.

Cultural myopias

There are several consequences of this:

One is that we need to recognize when we are unnecessarily restricting our thinking to life like ours. It can be hard to “step out of brains” (as Nathalie Cabrol puts it) and imagine a truly alien civilization. In order to do it, we must understand what it is to be human, so we can imagine what we would and might not have in common with alien species. This is especially important if there are “beacons” out there: signposts of technological life designed to catch our attention. Finding these means finding Schelling points, which means understanding what it means to be intelligent and technological, and what we must have in common with other species in the Galaxy.

Even more than thinking like an alien, we need to be sure we are able to identify what it means to think like a human. A lot of the background and assumptions in SETI comes from stories we tell about how we got to be where we are now. For instance, when we discuss the “colonization” of the galaxy and the number of potential beacon transmission sites, we imagine an alien species—or humanity—traveling beyond their planet on ships, leaving the Shores of the Cosmic Ocean to settle distant shores, just as we have already done in our own modest ways on Earth’s oceans.

But what pictures come to mind when you think our history of this? Who are humanity’s quintessential colonists, the paragons of exploration?

The Mayflower colonists?

Christopher Columbus?

Landing of Columbus (12 October 1492), painting by John Vanderlyn


But, shouldn’t they be Ayla and Moana?

After all, humanity explored and settled nearly every habitable corner of our planet thousands of years before continental Europeans figured out how to navigate the open ocean.

The story of European history as human history—the story of the development of philosophy and science and technology and discovery as the progression from Ancient Greece to the Renaissance to the Space Shuttle—is a common one, but not representative of how technology on Earth as a whole actually developed.

In fact, this perspective is part of the theory of progressivist social evolutionism, now discarded by the social sciences that invented it, and one that justified a vision of European culture as the pinnacle of human civilization.

When we employ popularized and inaccurate accounts of human history like these to think about SETI, we are using partial and politicized stories to do science, and that’s sloppy, to SETI’s detriment.

And it’s not just history. A lot of our visions of human spaceflight and SETI come from science fiction, where many authors—including many influential scientists and engineers—have tried to broaden our minds to the possibility of what could be out there. But fiction is successful when it speaks to us—when the stories that are ostensibly about aliens have their real relevance to life on Earth.  The aliens in these stories are rarely really alien—they are usually allegories for “Others” on Earth, designed to explore humanity from an outsider’s perspective. That makes them fun to read, but it makes them guides of mixed utility, at best, for what might really be out there.

Doing SETI better

For all of these reasons, SETI needs to include the social sciences, especially anthropology, to help practitioners identify where they are stuck “inside their brains” and get out.  Anthropologists are trained to spot these sorts of cultural myopias and avoid them, from the books we read, to the language we use to describe our future and alien species.

That’s why anthropologist Michael Oman-Regan and I have written a paper about visions of SETI and human spaceflight.  We identify some of the tropes and language currently common in the fields, and trace some of them to their origins in science fiction and colonialist narratives (including an oft-cited (self-described) “white separatist”).

As we write in the paper:

Regardless of their personal politics, it behooves practitioners to know the origins of the terms they use and visions for the future they hold, and examine the biases they bring, both to avoid unacknowledged bias in a field that requires an open mind, and to ensure that the field itself is not excluding voices and perspectives that will also help it thrive.

Along the way, we recommend some science fiction to read, trace the “giggle factor” in SETI to camp in science fiction, provide over 60 footnotes of links, evidence, and asides (fun footnotes are a guilty pleasure of mine), and we cite a huge range of sources from Burtons (Tim, LeVar) to social science PhD theses to Avi Loeb.  We mention a lot of ideas that could be whole papers in themselves; we hope that it will inspire curiosity and more research into many of these topics.

I would do a big slow-blog introducing all the big points, but there are too many, and since the paper is very readable (I think so, anyway), instead I’ll leave you with the above teaser, and this link to the paper:



Parts of this post quote or paraphrase our paper, including parts written by Michael Oman-Reagan. Any inaccuracies are my own.

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!

Schelling Points in SETI

How do you find someone who is also looking for you if you can’t communicate with them?

I was reading the Wikipedia article on the water hole concept in SETI, and saw under “see also” the entry “Schelling point“. Investigating led me to a fascinating bit of history.

Thomas Schelling

Thomas Schelling is a heterodox economist and foreign policy expert who won the Nobel Prize for applications of game theory to conflict. His analysis of the game theory behind nuclear warfare led to the concept of “mutually assured destruction” (with the appropriate acronym MAD) which had great influence (for better or for worse) on the nuclear arms race. His demonstration of the power of being “credibly irrational” does a lot to explain North Korea’s foreign policy. His concept of “tipping” explained how racial segregation can arise from small preferences even in the absence of government-sponsored redlining, which continues to have strong influence on housing policy.

In his seminal 1960 work The Strategy of Conflict he described a game in which the players must cooperate but cannot communicate. In order to work together, they must guess at each others’ strategies, and make sure that their own strategies are guessable. This means they should not pick the objectively best strategy, necessarily, but they should pick the strategy that is most likely to be guessed by the other—assuming they think the same way, one ends up with an infinite recursion!  But all is not lost: if you have something in common with the other player some strategies are clearly superior to others.

For instance, suppose the game is to find the other player in New York City. They are also looking for you, but you two have no way to communicate with each other. Is it reasonable to wait in a restaurant at the corner of 3rd Ave and E 56th street until they show up? No—not only is that not a particularly meaningful place, if they similarly pick a (different) random spot in the city and wait for you, you will never find each other. But there are better strategies: if your partner in the game knows anything about New York (and since they are somewhere in New York, they could ask even if they don’t) then there are certain places and times they are more likely to guess.  Landmarks like Grand Central Station and the Empire State Building are more likely common guesses than random restaurants, and times like noon are more likely for meeting up than 3:12am.

In other words, by thinking about the sorts of common knowledge you share with your partner, you can narrow down the infinite range of possible strategies and have a fighting chance of finding your partner.  The point isn’t that you could win this particular game, it’s that even in the absence of coordination there is a hierarchy of strategies, and they have more to do with the players (what they know) than the game itself. It was a brilliant insight, and the concept today is called a “focal point”.  This already has an unrelated definition in astronomy, so I prefer the (also common) term “Schelling point”.

Incredibly, even though the book was published in 1960, it contains a footnote about SETI, which had its first paper published in 1959!  He writes:

[A good example] is meeting on the same radio frequency with whoever may be signaling us from outer space. “At what frequency shall we look? A long spectrum search for a weak signal of unknown frequency is difficult.  But, just in the most favored radio region there lies a unique, objective standard of frequency, which must be known to every observer in the universe: the outstanding radio emission line at 1420 megacycles of neutral hydrogen” (Giuseppe Cocconi and Philip Morrison, Nature, Sep. 19, 1959, pp. 844-846). The reasoning is amplified by John Lear: “Any astronomer on earth would say ‘Why, 1420 megacycles of course! That’s the characteristic radio emission line of neutral hydrogen.  Hydrogen being the most plentiful element beyond the earth, our neighbors would expect it to be looked for even by tyros in astronomy'” (“The Search for Intelligent Life on Other Planets,” Saturday Review, Jan. 2, 1960, pp. 39-43). What signal to look for? Cocconi and Morrison suggest a sequence of small prime numbers of pulses, or simple arithmetic sums.

This is amazing!  I’m guessing Schelling was reading his weekly Saturday Review when he came across the article, thought it was a great example of his point, and added the footnote to his manuscript for the book, which was published later that year.

This idea has been re-invented over and over in the SETI community. Filippova called it a “Convergent strategy of mutual searches” in 1991, and before that in 1980 Makovetskii called it a “mutual strategy of search,” and a “synchrosignal” in 1977.  Guessing the “magic frequencies” at which ET might be transmitting (it was “pi times hydrogen” in Contact), where they might be transmitting, and when they might be transmitting is an exercise that founds many SETI papers.

My favorite example is Kipping & Teachey’s suggestion in their “laser cloaking” paper.  The paper is mostly about how lasers could be used to sculpt transit light curves to hide or amplify the signs of biology or technology (or of the planet itself!), but it also points out that the best time to transmit is during the time your target would see your planet transit your star (so stars exactly 12h from the Sun; especially those on the ecliptic).  This is a great Schelling point: it is an obviously special time in a planet’s orbit, it doesn’t require the transmitter or receiver to know the precise distance to each other to account for light-travel time and synchronize their efforts, and has the bonus that one might catch the attention of astronomers observing the transit for purely natural scientific reasons.

But this all goes back to Schelling and brings us to the central insight: if there are alien civilizations out there trying to get our attention, we are more likely to find their signals if we can “think like them” and ask “what can we assume they know about us?” The logic that if we have radio telescopes we will know about the 1420 MHz line is pretty solid. Mathematics seems like something we must have in common if they are technologically advanced enough to send interstellar signals, but I’m skeptical that they would find find primes as fascinating as we do (and if we assume they like pi we miss out on them if they are actually tauists).

It’s a nice illustration of how SETI forces us to look inward, as well as out, and question what it means to be human, so we can imagine what it might mean to be an alien. Since these are questions of the social sciences, it shows that SETI is much more than a physical science or engineering challenge, and needs to include anthropologists, linguists, mathematicians, and others.

You can read more examples of people suggesting Schelling points in SETI in my review chapter on exoplanets and SETI here.

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.


Tabby doing a Q&A on the WTF star on Twitter

Tabby just did a 20-questions-and-answers thing on Twitter.  I found it hard to read the whole thread, so I’ve compiled it here.  Enjoy!



Two New Tabby’s Star Papers

Amidst the huge task of collating all of the data coming in from the May 20, 2017 dip, two papers have hit the arXiv.  I don’t have any updates on the data from the dip (we haven’t had time to do any detailed analyses yet), but the live chat I did on Friday is still mostly valid:

except to say that the dip has maybe ended:

Today there are two new papers on the arXiv on the subject.  I haven’t had time to do deep dives on them (and neither is refereed yet) but here are my hot takes:

The first is by Ballesteros et al. (MNRAS, submitted) and they try to model the dips with a gigantic planet with a huge ring system and huge swarms of trojan asteroids.  In other words, their model puts a lot of stuff in a 6 au orbit around the star, which is far enough away that it would be pretty cold.  They point out that the deep, asymmetric dip at Kepler day 793 occurs about half way in the middle of a pretty quiescent period for Tabby’s Star.  They associate the other dips with swarms of trojan asteroids—asteroids in the same orbit as the planet but leading or trailing the planet by 60 degrees.

Some strengths of the model:

  • They claim that they can model the deep D793 event as a giant (0.3 solar radii!) planet with a tilted ring system and that they will do this in a later paper
  • They get the overall pattern of the dips explained: Kepler just caught the back of the pack of leading trojan asteroids when it started observing, then the planet at day 793, then the trailing swarm at the end of its mission
  • In what must have been a hastily written addition, they attribute the May 20 event to a secondary eclipse of the planet behind the star. This comes with a prediction: the event will be no longer than the D793 event (which was actually very long), but they say no more than 2-4 days.  They say that the secondary eclipse depth could be as deep as 3% (about what we see).  I note it should also be pretty achromatic, unless the reflectivity of the planet is a strong function of wavelength.
  • They emphasize that their model appeals only to likely, conventional astrophysics (though when it comes to 0.3 solar radius planets and a Jupiter-mass of asteroids in a swarm, your mileage may vary on that one).
  • They have a really nice diagram!

Some drawbacks:

  • They need a lot of asteroids: they don’t actually say how much, but the number they do give is huge: over a Jupiter mass of them!  It’s not clear to me how stable such a swarm could be co-orbital to an actual planet.  Part of the reason Jupiter’s trojan asteroids work as they do is that they don’t really perturb Jupiter. Also, how do you keep a Jupiter mass of material from collapsing or falling into the planet?  Also, where would you get a Jupiter mass of rock?!
  • They cannot explain the secular dimming seen by Montet & Simon and Schaefer, which they say must have a different cause.
  • They do not confront the infrared and mm upper limits, especially those of Thompson et al. (whom they do not even cite) that put no more than a millionth of an Earth mass of dust hotter than 160K.  I would think that an asteroid swarm dense enough to have an optical depth near 1 along some lines of sight (22% dips!) would also generate some serious dust, as would those rings.
  • They will need a pretty strange sort of planet to have a detectable secondary eclipse out at 6AU.  They claim that a Bond albedo of 0.34 will do it, but my back-of-the-envelope calculation says no way this could work (a perfectly reflective 15 solar radius circle (for the ginormous rings of this planet) at 6 au intercepts about 1 ten thousandth of the stellar flux, not 3% of it).  If it’s really emitted light then it should be pretty red, so the May 20, 2017 dip should be hard to see in the blue.
  • I think the slopes of the dips are too steep; material at 6 au moves pretty slowly. They could easily calculate this.

But kudos to them for putting an idea out there with concrete predictions!

The second paper is by J. Katz.  I’m glad to see this one in principle—Steinn and I suggested an object in the outer solar system could be responsible and hoped someone would work that out, and here’s a paper working it out!  Weirdly, Katz cites us but don’t mention our suggestion.  Anyway glad to see it.

This is a strange paper, though. There is no comment that it has been submitted to any journal to be refereed—it’s possible this is all we get.  It’s called “Tabetha’s Rings”—I don’t think I’ve ever seen just a modern astronomer’s first name in a paper title before.  Katz refers to the star as “Tabetha’s Star” which is also strange (because the star needed another name, right?).

Katz suggests that a ringed object in the outer solar system could be responsible for the dips…and not much else.  Some of the implications are worked out, but some of the math seems wrong to me (he predicts that the dips will be visible every 365.25 days from earth, which ignores the orbital motion of that object).  I kept expecting Katz to bring up the rings of asteroids but it never came up.

Anyway, I hope Katz develops this model further and describes things like the spectral and photometric properties of the dips his model implies, and discusses, for instance, the mass of the object hosting the rings (at least!). I’d really like to see a fleshed out version of this paper in the refereed literature.

OK, the kids are off to school so time to get back to the disaster area that is my inbox…

Activity from calcium

The atmosphere of the Sun (and other stars) contains calcium. It contains most of the elements, actually, just like the Earth does. As light that emerges from the sun passes through this cooler atmospher, two specific colors of very blue light, corresponding to specific transitions of electrons in a calcium ion, have a hard time getting through because they get absorbed by the calcium. These colors are “missing” from the solar spectrum, and Fraunhofer, who established much of our notation for spectral features, labeled them “H.” Later astronomers gave the two wavelengths separate names, and today we call them the H and K lines.1

The sun is “dark” at these wavelengths (this light doesn’t get through the lower atmosphere), so the much hotter upper atmosphere of the sun (the chromosphere) stands in good contrast against it, especially because the chromosphere is bright at these wavelengths (this is not a coincidence—the same transitions that make calcium in the lower atmosphere a good absorber make the upper atmosphere an efficient emitter at the same wavelengths.)

National Solar Observatory image of the sun in the wavelength of the ionized calcium K line.

You cannot see the usual “surface” of the sun at these wavelengths; that light has all been absorbed by calcium ions. In this image you are looking at the upper atmosphere of the sun.  Here, the brighter regions are hotter, and they tend to cluster around sunspots.  This is because sunspots are caused by intense magnetic fields on the sun, and these fields reconnect and deposit energy high in the sun’s atmosphere, heating it and making it shine at this wavelength. The sun has an 11-year activity cycle, and if one makes measurements like in this image, one can clearly see this cycle as the total number of sunspots rises and falls over the course of a decade.

Now, in other stars we cannot see sunspots, but we can measure the amount of H and K line emission.  Imagine this image of the sun was taken from so far away, you could not make out the sun’s disk.  The five bright “active” regions (near the sunspots) would add up to make the point of light that is the sun look brighter at this color than it would if those regions weren’t there.  This means that you could tell how much magnetic activity—sunspots and related things—was going on on the sun by how bright it was at this color. Watch long enough, and you could tell that the sun had activity cycles!

This is the philosophy behind the pioneering Mount Wilson H & K project, undertaken by Art Vaughn, George Preston, Sallie Baliunas and many others from 1966-2002.  They measured the brightness of around 100 sun-like stars for decades to watch the rise and fall of their activity levels.  The technique is now used at many observatories.

One of the big things people look for is an analog to the solar Maunder Minimum, a period from just after the discovery of sunspots by Galileo lasting about 70 years during which there were almost no sunspots. No one knows why the sun apparently stopped its magnetic cycle for so long, but if we could catch another star doing it, then maybe we could figure it out. The Mount Wilson project identified several sun-like stars with no sunspot cycles—victory!

But in 2005 I published a paper as a graduate student showing that this was actually a mistake. All of these “Maunder-minimum-like” stars had had their distances measured since the Mount Wilson project made their discovery, and most or all of them all turned out to be much farther away than expected—which means they were much brighter than we thought.  Why? Because they’re not really much like the sun—they are subgiants, not ordinary main sequence stars, and we don’t expect subgiants to have strong magnetic fields.2  So it turned out the Maunder minimum was still sort of a mystery.

But wait!  In star clusters one knows the distance to all of the stars, so one won’t get fooled by subgiants.  Mark Giampapa and others have looked at truly sun-like stars in M67, an open cluster of stars a lot like the sun, and found that some of them have calcium H & K emission way below what the sun has even at solar minimum—there they are! Maunder-minimum-like stars!

Jason Curtis, now an NSF postdoctoral fellow a Columbia University

In an amusing symmetry, my former graduate student, Jason Curtis, has looked into this and discovered that because M67 is so far away, you have to worry about another source of absorption: the interstellar medium.  This gas between the stars is very sparse—the Mount Wilson stars are all too close to have their light affected by it.  But M67 is very far away, and there is a lot of this gas in the way. This gas is made of the same stuff everything else is—including calcium!

Maybe you can see where this is going.  The calcium in the interstellar medium absorbs calcium H & K light, making the stars appear dimmer at those wavelengths, and so our magnetic activity measurements end up giving erroneously low values. Once you correct for that absorption, it turns out that there aren’t really any anomalously inactive stars in M67.

So Jason’s new paper on this topic points out that, once again, stars that we thought were good Maunder minimum stars are, in fact, not—in this case, they’re just behind more interstellar calcium than we’re used to seeing in front of nearby stars.

You can read his (single author!) paper here on the arXiv now that it has been accepted to the Astronomical Journal.

1Jay Pasachoff pointed me to this history of notation for the H & K lines. Fraunhofer did not discover them, and the “K” line terminology came much later.  Jason Curtis points me to this amusing mistake, where the letters are misinterpreted as standing for “hydrogen” and “potassium”.

2More on this, including an amusing anecdote about a “Marshall McLuhan moment” at my first colloquium, here.

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.


On Outré Ideas

David Stevenson has a nice Commentary in Physics Today:

He argues in defense of “crazy” ideas in science. He categorized three kind of “crazy”:

The First Kind is simple crackpottery: people who don’t know enough science to articulate a real scientific idea, and do not understand its interconnectedness well enough to distinguish outré ideas from nonsense ones. He says this is the most common and least interesting (and he’s right, except as a study in sociology)

The Second Kind is when good scientists take a fresh, naïve look at a new field. He writes:

Inevitably, such excursions can look like the actions of a dilettante…One is then accused of speculation. I occasionally sense from colleagues some disdain for scientific speculation, perhaps because it is cheap: It seems to require relatively little effort and commitment.

He argues that hard, serious speculation is rare and important. This is certainly something I’ve tried to engage in. My excursions into lunar geology theory, the Faint Young Sun problem, and even SETI (at first) were certainly in this category. Indeed, the reactions I got to our lunar highlands work from the lunar science community ranged from the pleasant to the snide (Dave himself was polite, but dismissive—though, after reading this I wonder if I misread him.  Caltech GPS was certainly the most receptive audience I found.).

Physicists are prone to this sort of work (consider Richard Muller’s forays into climate science (and borderline denialism)) to the point of cliché (one of my favorite SMBC comics), and SETI seems to be a favorite destination for dilettantes from all fields.

The Third Kind are when established leaders in their fields upset the table with entirely new perspectives.  One occasionally sees cals for such ideas: Lindy Elkins-Tanton acknowledged the need for new ideas in lunar formation theory in Nature, and Michael Inzlicht in psychology has done serious soul searching, wondering if his career, indeed much of his field, is based on bad statistics. But these ideas are not always invited or even welcome; Stevenson’s examples are Hoyle’s Black Cloud and steady-state cosmology, and the idea of emergent gravity.  He finishes with a quote from Neils Bohr to Wolfgang Pauli: “We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct.”

Stevenson briefly mentions a “portfolio” of ideas, and this brings me to one of my favorite papers, Avi Loeb’s banquet lecture (here at Penn State!) about how young scientists should divide their research time. He argues for some fraction of time to be spent on “venture capital”, analogous to spending some of your financial portfolio on high-risk, high-reward investments. (Avi may have been inspired by Eric Weinstein’s lecture on the topic, h/t Michael Neilson for pointing me to it) Avi acknowledges that there is actually a lot of acceptance for work on outré topics, but argues that the natural conservatism of the Academy and science tends to favor no more than 5% of one’s efforts there.  He argues it should be more like 20%.

I think between 5-20% is right, in an average sense. So some scientists should spend 100% of their effort on safe “bonds”, others a lot more on venture capital (my last few years have involved much more SETI than I had planned for), but if as a whole we’re working between 5-20% of the time on Second and Third Kind speculation, I think we’ll do well.

I use “outré” above instead of “crazy” (and I put the latter in scare quotes) because the latter is a slur for people with mental health issues. I appreciate it’s often not meant that way, but I think society is slowly realizing how common mental illness is, how badly and unjustly it is stigmatized, and how casual uses of terms like “crazy” to mean “unexpected” or “weirdly different” reinforce that stigma.  Also, “crazy” isn’t even the right word here—by using it, Dave is facetiously implying that one would have to be mentally ill to have come up with the idea, but all he needs to make his point is to say that it’s nonobvious, very clever, and outside the normal thought process—outré.

Przybylski’s Star V: Origins of the Idea

Part V/III.  Part I is here.

The earliest reference I cited to the idea of artificial species in stars was from Howard Bond, who said he thought Shklovski & Sagan dealt with it in their book.  I finally got my hands on a an early edition.

It looks like Frank Drake and Iosif Shklovskii were first with this idea.  From the 1966 edition of Shklovskii & Sagan’s “Intelligent Life in the Universe”:

…we should mention independent suggestions by Drake and Shklovskii that, if not the communication of large amounts of information, at least the communication of the presence of a technical civilization, can be effected through the use of markers.  Drake and Shklovskii envision the dumping of a short-lived isotope—one which would not be ordinarily expected in the local stellar spectrum—into the atmosphere of the star. In any case, the material of the marker should be of a type that is difficult to explain, except as a result of intelligent activity.

They conclude with a sentiment I tried to articulate at the end of Part IV.

Remarkably enough, the spectral lines of one short-lived isotope, technetium, have in fact been found in stellar spectra. Its half-life is around 2×105 years.  However, technetium lines have not been found in stars of solar spectral type, but rather oly in peculiar stars known as S stars.  In fact, as we saw in Chapter 8, the discovery of technetium in the S stars have been used as an argument for contemporary stellar nucleosynthesis.  This example illustrates on of the difficulties with such a marker announcement of the presense of a technical civilization.  We must know a great deal more than we do about both normal and peculiar stellar spectra before we can reasonably conclude that the presence of an unusual atom in a stellar spectrum is a sign of extraterrestrial intelligence.

I see this as a feature of artifact SETI: anomalies are inherently interesting.

When to Violate Confidentiality of Peer Review

Peer-review is an important part of scientific communication. It is not a panacea and is quite fallible, but it serves several functions well:

  1. It gives journals a “filter” against unprofessional work (including crankery and its cousins)
  2. It gives authors and editors the opportunity to receive unfiltered feedback on how a paper will be received. The “unfiltered” part is ensured in part by the anonymity of the referee (which the referee can waive).
  3. It provides a fresh set of eyes from an expert who can help spot errors and mistakes
  4. Ideally, it gives authors constructive feedback to improve their work
  5. It does all of this confidentially, so when science is finally presented to the world it has already been vetted and mistakes have been fixed (this step is optional for authors—they can post preprints whenever they like).

Refereeing papers is an unpaid service to the community that scientists provide. I think of it like jury duty: I rely on good referees to fairly judge and improve my papers, and so I try to write at least as many referee reports as I receive, and be the sort of referee I hope I’ll get on my papers (I have to referee more than I am refereed because some scientists are very bad referees (slow, delinquent, unduly harsh, sloppy, etc.) and the rest of us need to pick up their slack.

The confidentiality of the process is important to the journals, and to some authors and referees. For the authors, this means they do not need to worry that their work will be scooped, that their mistakes have a chance to be fixed before they are made public, and that they have a chance to respond to any unfair criticisms in a report. For journals, this confidential review process is one of the primary values they add to papers (some of the others being editing, typesetting, publicity, and curation). For referees, it means they can frankly help improve the literature without being concerned about the reaction of the paper’s authors.

There are other ways to do this; there are good arguments for entirely open peer review, as well.

One interesting issue is whether the referee should be bound by confidentiality. There are good reasons why a referee might feel they should publish their review. This is especially true in instances where there is evidence of fraud, for instance. The case is made here:

The argument is that there can be good reasons to publish your report (as open peer review shows; read the article), and because the referee holds the copyright to the review.

But in the AAS astronomy journals, confidentiality of referees report is explicitly part of the journal ethics statement that binds referees and authors. Referees thus promise to keep the reports confidential.

Of course, this could lead to an ethical dilemma if publishing the referees report would improve science. But I think there are many perfectly ethical routes one can take to avoid that dilemma:

  1. Polish the relevant parts of your referee’s report, make sure it only refers to the published paper, and not the (strictly confidential) manuscript, and publish that on the arXiv as a “comment”.
  2. If the content of the manuscript needs to be mentioned, go directly to the editor. The purpose of confidentiality is to preserve scientific integrity; the editor has the authority to waive confidentiality, or take other actions to rectify the problem.

For instance, a climate science journal Environmental Science Letters rejected a paper by a climate skeptic, Lennart Bengtsson, on the basis of two very unfavorable referees reports that heavily criticized the science. The reports even offered suggestions for how to improve the paper and make it publishable.

Prof. Bengtsson cherry-picked a few words from one of the reports and (violating confidentiality) complained to the media that the paper had been rejected because of its conclusions for political reasons.

The journal, in this case published a rebuttal that included the entire referees reports, exposing the mendacity of Prof. Bengtsson’s accusations. Review confidentiality is at the discretion of the editors, so they can (and should) waive it when it is not serving its purpose (preserving scientific integrity).

If, for some reason, the editors were to enforce the confidentiality to the detriment of scientific integrity, then a referee may need to violate the rules and publish their review.  In this case, I recommend checking (confidentially) with others familiar with the issues, especially an ethicist, to make sure you are in the right.  After you post your report, the journals may complain, and you may face repercussions from your professional society, but if on balance you are behaving ethically you will have a good defense.

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.