Giant Planets Transiting Subgiants

It’s been a while since I’ve discussed the subgiant mass issue, but there’s a nifty new paper out that gives me occasion to revisit it (original controversy, our response, another mention here). The basic outline is that there is a mild controversy over the masses of subgiant stars — stars transitioning between their long Main Sequence lives and their final, giant phase before they run out of nuclear fuel. John Johnson studied subgiants that were between 1.5-2 solar masses back when they were on the Main Sequence (“Retired A Stars”) to show that they are more likely to have giant planets detected around them than stars of the Sun’s mass or lower. Jamie Lloyd at Cornell thinks these are really mostly just solar-mass stars, because there shouldn’t be very many retired A stars (it’s a short phase of a rare kind of star). After refereeing the discussion between my friends for a while, I finally sided with John.

Since then, Luan Ghezzi and John have a nice paper where they look at all of the subgiants with known masses and find that there is no reason to doubt their mass estimates.

But what we’ve really wanted to have is a transiting planet around a subgiant. Transiting planets provide a way to estimate the density of a star completely independently of other methods, which, combined with even a rough radius estimate, would allow a subgiant’s mass to be independently estimated.

The problems are many: subgiants don’t have a lot of close-in planets, they’re big, so the transiting planets have very small depths, and they’re big, so the transits are looooooong.

Prof. Josh Pepper of Lehigh University.

Prof. Josh Pepper of Lehigh University.

Well, the KELT team has found one, and around a bright subgiant!  Josh Pepper leads the team that just announced KELT-11 b, an inflated  0.2 Jupiter mass giant orbiting a V=8 star.   KELT is the “Kilodegree Extremely Little Telescope” array, designed to scan huge swaths of sky for transiting planets. Its architects include Thomas Beatty of Penn State, Jason Eastman now at Harvard, and Scott Gaudi at Ohio State, to name a few of those I’ve worked closely with.

KELT-11 is brightest star known to host a transiting planet in the southern hemisphere!  The paper has a ton of authors because a big team of people worked really hard to get this star characterized. I’m involved because MINERVA contributed some photometry (fourth curve in figure 2) to try to nail this thing down.

Screen Shot 2016-07-07 at 9.09.19 AMBecause it’s a subgiant, the signal is very weak, and very long.  The transit is eight hours long, which means that virtually no single telescope on Earth can get the whole transit in one night (we don’t have any south pole photometers!).  As a result, it’s challenging to remove systematics from ground-based observing: you never see both ingress and egress with the same data set.

A precise mass from the transit alone will still need to wait for space-based data that can get the entire transit in one go, but in the paper the team uses several independent methods to estimate the mass, including their best estimate from the light curve.  In section 3.8, four different estimates are used and all four find a mass > 1.3 solar masses, with the right answer probably around 1.4. This further confirms the methodologies John uses to estimate masses, giving more evidence to the assertion that the subgiants in his sample really are “Retired A Stars”.

It’s a great paper about a superlative planetary system ripe for extensive followup.  You can find it on the arXiv now here:

KELT-11b: A Highly Inflated Sub-Saturn Exoplanet Transiting the V=8 Subgiant HD 93396

We report the discovery of a transiting exoplanet, KELT-11b, orbiting the bright (V=8.0) subgiant HD 93396. A global analysis of the system shows that the host star is an evolved subgiant star with Teff=5370±51 K, M=1.438+0.0610.052M, R=2.72+0.210.17R, log g=3.727+0.0400.046, and [Fe/H]=0.180±0.075. The planet is a low-mass gas giant in a P=4.736529±0.00006 day orbit, with MP=0.195±0.018MJ, RP=1.37+0.150.12RJ, ρP=0.093+0.0280.024 g cm3, surface gravity log gP=2.407+0.0800.086, and equilibrium temperature Teq=1712+5146 K. KELT-11 is the brightest known transiting exoplanet host in the southern hemisphere by more than a magnitude, and is the 6th brightest transit host to date. The planet is one of the most inflated planets known, with an exceptionally large atmospheric scale height (2763 km), and an associated size of the expected atmospheric transmission signal of 5.6%. These attributes make the KELT-11 system a valuable target for follow-up and atmospheric characterization, and it promises to become one of the benchmark systems for the study of inflated exoplanets.

Comments: 15 pages, Submitted to AAS Journals
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1607.01755 [astro-ph.EP]
(or arXiv:1607.01755v1 [astro-ph.EP] for this version)
B.J. Fulton, University of Hawaii graduate student

Three New Neptunes

One of my looooooooooooong term projects is monitoring the bright stars in the sky for yet more exoplanets.

These bright stars are some of the very closest Sun-like stars in the sky, and primary targets for next-generation efforts like MINERVA and NEID.  Because of their proximity, their planets are the most easily imaged cold planets, the most easily weighed by astrometric measurement (someday), and (even further in the future) the only ones humanity can plausibly target with interstellar probes. We will study these systems for as long as we pursue astronomy.

PSU Professor Eric Ford (but I knew him before he was famous, back in our Berkeley days)

PSU Professor Eric Ford (but I knew him before he was famous, back in our Berkeley days)

For a few years Eric Ford and I routinely submitted proposals to NExScI to continue monitoring these stars at Keck, and for a while we were successful. It’s a hard sell to a competitive TAC, though, and once Kepler targets started (deservedly) getting lots of NASA Keck RV time, it didn’t make sense to keep proposing.

While it’s not as quick and flashy as Kepler science can be, there are three big ways this sort of patient astronomy pays off: finally getting orbits for long period planets (as in this paper by my student Katherina Feng), monitoring planet-planet interactions among known exoplanets (as in this paper by Ben Nelson), and getting enough data to find new low-mass planets orbiting these stars.  

B.J. Fulton, University of Hawaii graduate student

BJ Fulton, University of Hawaii graduate student and author of a nice new paper on some familiar systems.

Well, a lot of that Keck time we invested (combined with a lot of UC and Hawaii Keck time, plus APF time) has paid off yet again. BJ Fulton, a graduate student at Hawaii with Andrew Howard, has just posted his latest paper announcing three Neptune-massed planets orbiting bright, nearby stars.  There’s a lot in here!

First, HD 42618: it’s a solar analog (1.05 solar masses) at 24 pc that undergoes a magnetic activity cycle (something we can detect when we monitor stars for decades!  It also helps to have Greg Henry’s photometry for this.) There’s CoRoT photometry, so the team was able to extract asteroseismic information to confirm the stellar parameters. The new planet orbits near 0.5 AU, and receives 3x Earth’s insolation from its star.  Interestingly, BJ had to remove the stellar activity cycle from the RV time series to get to the planet: the amplitude of the effect is 3 m/s.  That’s not abnormally high, but high enough to be annoying.  There is also a signal at 2 m/s and P=388 days: this is close enough to 365 days to be both suspicious and difficult to check; if due to another planet, that one is at least 22 Earth masses.

Next up: HD 164922, a G9 star a 22 pc.  Here, interferometrists were able to actually determine the radius of the star directly, greatly improving our stellar parameter estimates. Back when I published the Catalog of Nearby Exoplanets, we included in that paper the announcement of HD 164922 b, a P=3-year giant planet. In 2007, as part of my thesis I published a paper in which we noted that we saw a hint of a low amplitude second planet:

— HD 164922 has a known planet with a 3.1 y orbital period. For this star, the FAP
for a second planet is <1%. The best fit for this second planet has P = 75.8 d and
m sin i = 0.06 MJup. The amplitude of this signal is extremely low — only K = 3 m/s —
making this an intriguing but marginal detection.

As luck would have it, this signal was real! BJ finds P=75.8d and K=2.2 m/s — no wonder we had such a hard time picking it out back in 2007!  What a difference 9 years of concentrated RV work makes.

The last one is ρ CrB (HD 143761), a V=5 G0 star only 17 pc away.  The first planet around this star was detected back in almost 20 years ago (Noyes et al. 1997!) — one of the very first exoplanets.  This was back when there was a lot of discussion (too much, in fact) about some or all of the detected exoplanets being face-on stellar binaries.  More than once, astronomers pointed to astrometric data suggesting that the signal Noyes et al. saw was from a face-on brown dwarf or stellar companion. Now, this in itself was really interesting, because brown dwarfs were only known for about 2 years when ρ CrB b was discovered!  But not as interesting as exoplanets.

Well, not only do we not see any evidence of a stellar companion in interferometry or speckle imaging, but BJ has found a second planet in the system, and he shows that stability constraints make it very unlikely that there is a big old brown dwarf down there — ρ CrB b is almost certainly a planet.

Seeing these planets published is so rewarding—an example of literally decades of work coming to fruition. Seeing these old systems again is sometimes like seeing old friends after a long time and meeting their young families.

You can find the full paper on the arXiv here.  You can email BJ with questions or complements about the paper here.


Right on Red

A traffic issue has vexed me for years, and we finally got to the bottom of it.

There are two signs in Pennsylvania that have always made me nervous to turn right at a red light: “stop here on red” and “right turn signal”.


Here they both are at the corner of East Branch Road and South Atherton street near my house:

Screen Shot 2016-06-22 at 1.44.52 PM

This is the Google Streetview view from the right-turn only lane.  The sign on the right is pretty clear: on a red light you stop there, at that line.  BUT… is there an implication that you must stay stopped until the light turns green? I always assumed no, but couldn’t be sure.  Is the sign merely telling motorists where they must stop when they do for a red light, or is it an imperative to remain stopped? A case could be made either way, and presumably traffic law settled the question long ago.

Then there’s the second sign by the lights.  Here’s a better view of it:

Screen Shot 2016-06-22 at 1.43.52 PM

This one also seems pretty clear: the two lights on the right of this five-light signal are for people turning right. Indeed, in states where lights are shaped like arrows instead of circles, there is no need for such a sign.

BUT…does that mean that if I want to make a right turn, I have to obey that signal, thus negating the usual right-on-red rule? After all, in states with arrow-shaped lights for right turners, there is also a red arrow. If this sign thus turns circles into arrows, then right turners must remain stopped until the right green light is activated. Or does the sign only refer to the yellow and green light, not the shared red?  In that case, there is no red light for right turners!  The case for no right on red here is actually pretty strong, but still ambiguous.

Either sign alone, and I would take the right turn without too much worry.  But together, these two signs always made me worry that a police car would catch me turning right on red and ticket me.  Friends had told stories about how other friends had gotten tickets for rights on red when one of these signs was present, but I assumed that was somehow from some more complex or distinguished case.

Well, a discussion with friends finally got me to do some research online, while my wife Julia just did the right thing, calling the police to ask.

I found this, which reads authoritatively on the subject:

Also, the PA drivers’ manual says nothing about such a sign that would prohibit right on red:

Less authoritatively, every forum I can find online agrees that right on red with the “right turn signal” sign is allowed. For instance:

To top it off, Julia reports that the State College police department gets these questions all the time.  The bottom line:

Neither sign implies that you cannot turn right on red.  The only sign that prohibits otherwise legal rights on red is this one:


You’re welcome.

Next time on AstroWright: Traffic Detective: at how many intersections will one person have the opportunity to legally execute a left-on-red in a lifetime?



Screen Shot 2016-06-16 at 9.08.00 AM

Citizen Science

Can citizen science include Kickstarter-like campaigns for certain projects?

It’s a fascinating proposition. Success rates for NSF and NASA grants are below 20% (and in some cases, below 10%), meaning that even outstanding, high-impact, low-lisk research has a low chance of getting funded. Sites like have offered scientists ways to fund their research using a Kickstarter model: ask the public to pitch in.

For this to work, a project needs to capture the public’s attention. KIC 8462852 certainly has, and after a lot f recommendations on the topic, Tabetha Boyajian decided to start a Kickstarter campaign to fund follow-up observations of it.

Things started slowly, but the effort has really picked up steam in the past 48 hours.  We have a Cool Worlds video about it, courtesy of David Kipping:

and I was asked to mention it at my recent panel discussion on SETI at the New York Academy of Sciences:

Screen Shot 2016-06-16 at 9.08.00 AM

and APOD gave us a boost on Monday.

I think it would be fascinating to see if $100,000 projects could be funded this way—in this era of incredibly tight funding landscapes, it’s clear that there’s an appetite for more (and different) science than the government funds. I would not advocate that we move over to such a model entirely of course—peer reviewed proposal are still the best way to move science ahead, especially in directions with merits that are difficult to explain in lay terms—but it’s something that seems to be getting more popular.

Will get get to $100,000?  Well, as I write this we’re at $92,000 and there’s 24 hours to go.  We’re achingly close.

Give us a hand, will you?

The logo for Tabetha Boyajian's Kickstarter campaign.

The logo for Tabetha Boyajian’s Kickstarter campaign.


Effects of a Young Sun on a Young Earth

I’m pleased to announce three out-of-cycle opportunities to work with Penn State astronomers — including me! — through the NASA Nexus for Exoplanet System Science.  This cross-disciplinary research network is soliciting applications due July 1 for Nasa Postdoctoral Program fellows to come to Penn State to work on projects that cross disciplines and NExSS teams. I’ll describe the two with me in these blog posts; the third is to work with Eric Ford on the statistical properties of exoplanets (read the ad!)

Before you apply, please contact us so that we can help you craft a winning proposal.


The first opportunity is at this link.  Here is the second opportunity to work with me:

Effects of a Young Sun on a Young Earth

There is a huge controversy in heliophysics/stellar astrophysics over the composition of the Sun.  This might be surprising, given how well we (think) we understand the patterns of abundances in the Solar System, and how well we can study the Sun’s photosphere, but it turns out there’s a fly in the ointment.

The Standard Solar Model has been a high point in stellar astrophysics for decades.  Helioseismology provides data that confirms the model to very high precision, with a tiny disagreement at the base of the convective zone, where the physics gets tricky and uncertain.  This model includes a detailed map of the abundances of the elements as a function of depth in the Sun.

Martin Asplund, scourge of the Standard Solar Model.

Martin Asplund, scourge of the Standard Solar Model.

Then, along comes Martin Asplund who carefully measures the abundance of elements in the Solar atmosphere with unprecedented care and detail, and he finds that some elements, in particular oxygen, have had their abundances overestimated by a lot.  This created, as the physicists like to say “tension” between the models and the data.

One solution to this problem is that the new abundances are wrong.  Another is that the Standard Solar Model has been wrong for decades, with offsetting errors that gave us a false sense of precision. The problem with this solution is: what’s the other offsetting error?

Steinn Sigurdsson pointed me to an intriguing possibility: maybe the Sun was more massive when it was young? This would have had many effects, including a larger buildup of helium in its core that would be inconsistent with helioseismic measurements.  But now that Asplund has “broken” helioseismology, maybe there’s some room to play here?

There’s not a lot of room to play with this: Brian Wood has been measuring mass loss in young stars and finds it’s too small to have much effect.  But those measurements are pretty uncertain, and the payoff here is big: the insolation of the planets goes as the fifth power (!) of the Sun’s mass (two powers from holding the planets closer and three from higher rates of fusion) so even a 1.01 solar mass young sun would have an important effect (5%) on their received flux when they were young.  In particular, a major problem in planetary science is the “Faint Young Sun paradox”: the young sun was 25% fainter than today, so how could early Mars and Earth have had liquid water?!  Perhaps this is part of the problem?

This is not a new idea; Sackmann and Boothroyd discussed it 13 years ago. But with the new Asplund abundances (and Bailey opacities) it’s time to revisit the problem.

Even if the young sun was faint, it was very active.  The repurposed Kepler mission K2 has been observing stars across a range of ages, seeing how their flare rates and energies vary with stellar age and mass. These are important inputs for models of the young Earth and Mars: high energy particles can have a big effect on young planets’ atmospheres.  Indeed, NExSS PI Vladimir Airapetian had a nice result on this recently with respect to the Faint Young Sun paradox.

Anthony Del Genio of the Goddard Institute for Space Studies

Anthony Del Genio of the Goddard Institute for Space Studies

Anthony Del Genio of the Goddard Institute for Space Studies is interested in extending the GISS ROCKE-3D global climate model to early (Archaean) Earth, and the inputs for that model include the spectrum of the Sun at early times—a spectrum K2 will help us understand, and that depends on the mass of the Sun at that time.

Are you a recent heliophysics or astrophysics PhD that would like to help is with this problem?  Please consider applying to our NPP opportunity by July 1. The arrangement we have in mind is that you will work at Penn State with me primarily, co-advised by Tony (including trips to GISS to work on the climate modeling side).

If you are going to do this, please get in touch with us directly so that we can help you craft a competitive proposal to NASA.

I hope to see you at Penn State!

Evaporating Planets and Exoplanet Interiors with JWST

I’m pleased to announce three out-of-cycle opportunities to work with Penn State astronomers — including me! — through the NASA Nexus for Exoplanet System Science.  This cross-disciplinary research network is soliciting applications due July 1 for Nasa Postdoctoral Program fellows to come to Penn State to work on projects that cross disciplines and NExSS teams.  I’ll describe the two with me in these blog posts; the third is to work with Eric Ford on the statistical properties of exoplanets (read the ad!)

Before you apply, please contact us so that we can help you craft a winning proposal.


Below is the first opportunity.  I blogged about the second one here.

Evaporating Planets and Exoplanet Interiors with JWST.

We don’t really know what the interior of rocky planets are like. Even the Earth’s interior is mysterious: we can’t really go down and sample it, and there are big arguments about whether the samples we get from volcanoes are representative.  As a result, we don’t really know whether the mantle well-mixed, and we don’t know the water content of the Earth’s interior to an order of magnitude!

But these questions matter: the origin of Earth’s volatile budget and its plate tectonics are both highly uncertain and key components of the story of its habitability.  We need to know answers to these questions about exoplanets, but that seems pretty unlikely considering we can’t even agree on the answer for Earth, for which we will always have much more information than distant exoplanets.

Artist’s impression of a planet helpfully preparing a representative, backlit sample of its interior for study by astronomers.

Enter Kepler.

Among the new classes of exoplanets discovered by Kepler, KIC 12557548 represents the prototype of one that has particularly caught my eye: “evaporating” planets, a subset of “ultra-short period” planets (with periods less that 1 day).

These planets show highly asymmetric light curves, typically orbit M or K dwarfs, and are apparently rocky planets (or their leftover metallic cores) being ablated or evaporated by the intense instellation of their host star.  This process is, in some cases, stochastic, giving rise not just to asymmetric transits but extremely variable depths:

Transits of KIC 12557548, from Fig. 2 of Rappaport et al. 2012

Transits of KIC 12557548 b, from Fig. 2 of Rappaport et al. 2012

KIC 12557548 is not alone.  At least three other similar planets have been detected, including K2-22 which is in many ways much easier to study.  Here, we have what appears to be representative samples of the interiors of exoplanet being spewed into space right where we can study them with spectrographs.

Can we do mineralogy of these materials? Can we study the hydration levels of the rock? Can we compute the volatile inventory of these planets’ mantles? Were these planets once habitable? Are these in fact the metallic cores of once-rocky planets, meaning that they likely once had magnetic fields?

Steve Desch introduces us to lots of exoplanets

Steve Desch introduces us to lots of exoplanets

I don’t know, but I’m dying to find out. Before he left for industry, PSU research associate Ming Zhao laid the groundwork for this study in coordination with Steve Desch’s NExSS group at ASU.  Steve’s group has been thinking hard about the infrared spectroscopic signatures of the minerals of these planets, and what they can tell us about the planet formation process, these planets’ past potential for habitability, and planet formation generally.

Neal Turner, another NExSS PI, has also been thinking about these effluents’ properties, their interaciton with their host star’s magnetic fields and winds, and, very importantly, how they might be affected by the intense instellation they receive.

Are you an emerging researcher in astrophysics or planetary science interested by this problem? Please consider applying to our NPP opportunity by July 1.  The arrangement we have in mind is that you will work at Penn State with me primarily, co-advised by Steve (including trips to ASU to work on the planetary science side) and Neal (ditto for JPL and the stellar effects side).

If you are going to do this, please get in touch with us directly so that we can help you craft a competitive proposal to NASA.

I hope to see you soon at Penn State!



Updates on Boyajian’s Star

It’s been a busy few weeks for studies of the fascinating star announced by Tabetha Boyajian’s team, KIC 8462852.


It’s official!  Tabetha Boyajian is leading a Kickstarter effort to fund long-term monitoring of KIC 8462852 (I’m on the team!).  The idea is to purchase time on LCOGT, a private network of small telescopes around the world.  These professional instruments can provide regular brightness measurements of bright stars like KIC 8462, and will be able to provide us with an alert if it starts doing one of its mysterious dimming events again.  It’s an important effort, and exactly the sort of expensive, unknown-probability, uncertain-payoff science that is very hard for conservative time allocation committees and grant proposal panels to approve.

The logo for Tabetha Boyajian's Kickstarter campaign.

The logo for Tabetha Boyajian’s Kickstarter campaign.

But it’s also the sort of fun and fascinating science that plenty of people would be willing to kick a few bucks towards, and if “plenty” times “few” turns out to be enough, we’ll be able to ensure that we don’t miss the next event.  Please go to the site and help us out!

An Atlantic Article

Ross Andersen from the Atlantic, who wrote the article that made Boyajian’s star famous, saw the recent back-and-forth by Schaefer and Hippke.  First, Schaefer showed that Boyajian’s star seems to have undergone a “century-long-fade.”  Hippke wrote a rebuttal, Schaefer wrote an acid response, and Hippke came back with a more careful rebuttal.

Kim Cartier

Kimberly M. S. Cartier a.k.a. @AstroKimCartier

Rather than write his own summary for The Atlantic, would I like to write it myself, he wondered?  As luck would have it, my PhD student Kimberly Cartier, who is starting her final year in graduate school, is pursuing a career in science journalism.  Would Ross be interested in a piece co-written by the two of us?  Sure, he said.

So Kim and I quickly whipped up a Google Doc and pounded out a story.  After some back-and-forth with Ross for style and content, it went up on The Atlantic’s website.  I think it came out really well!

You can find more of Kim’s science outreach and journalism at Universe Today’s weekly space hangout, at her blog, occasionally on Monday mornings at 98.7 the Freq, on on twitter at @AstroKimCartier.

Green Bank Time!

The Green bank 100m telescope, the largest steerable telescope in the world.

The Green Bank 100m telescope, the largest steerable telescope in the world.

The event that started Boyajian’s Star’s fame was when Ross Andersen met with Andrew Siemion in Washington after Andrew’s testimony to Congress about the search for life in the universe. At the time, Andrew, Tabby, and I had just recently submitted a proposal to NRAO to use the Green Bank 100 m telescope to “listen” to Boyajian’s Star for alien transmissions.  Ross wrote a nice article on the Congressional event based on an interview with Andrew.

That “fun talk”, included Andrew mentioning our Green Bank proposal, and the rest is history.

But whatever happened to the Green Bank proposal? Well, the TAC met before Ross’s story broke, so all they had to go on was our short proposal explaining why the star was weird.  Our proposal was not as compelling as Ross’s article, and they turned us down, “with prejudice” as the lawyers say.

NRAO has a scale for ranking proposals, prioritized ‘A’ through ‘C’ for proposals that are awarded time, to ‘N’ for those for which there’s just not enough time.  It turns out, there’s also a sub-basement on the scale: N*, meaning something like “rejected not for lack of time, but because the proposal is not worthy, even if time were available.”

N* is what we got.  We got the feedback shortly after the news broke, and we decided to try again the next semester.  With a lot of astronomers’ eyes on the star, we could argue that if there were a simple exaplanation, it would have been forthcoming by now.  We also got to mention the Schaefer/Hippke flap, and address some of the TAC comments from the first round.

Well, apparently it worked!  We were just awarded 25 hours of ‘C’ time for 2016B, and Andrew tells me that this means we will almost certainly be able to observe.  I’m looking forward to the trip to West Virginia with Tabby and Andrew to do some radio astronomy!

That’s all for now.  Stay tuned…

Lodén 1 Part IV: Clusters in the Era of Gaia

So last time we established that the putative middle-aged, nearby cluster Lodén1 is neither middle-aged, nor nearby, nor a cluster.

(That, by the way, was basically the title of our paper, but the referee really disliked it (they thought it was confusing to call it a cluster then say it isn’t a cluster). Then the copyeditor went and changed all of our “amongst”s to “among”s.  Ah, well.)

We still need to take a look at NGC 2240 just in case, but frankly it’s pretty obviously not a real cluster, so it’s a low priority.  Also, Gaia is coming, and it will make this whole endeavor much easier.

The rest of this post is some thoughts by Jason Curtis on the topic:

While Lodén 1 does not appear to be a real cluster, the existence and recent realization that Ruprecht 147 is the oldest nearby cluster suggests that similar clusters might have also gone overlooked. As we say in our paper, “the utility of such clusters for stellar astrophysics demands that we find them.” This fall, the European Space Agency will begin releasing high-precision position and velocity data produced by its Gaia mission, starting with the brightest 2 million stars that were observed by the Hipparcos satellite in the early 1990s.

This first catalog will reach stars like the Sun at distances of up to 1000 light years, including the majority of the proposed candidates of Lodén 1 and the membership of Ruprecht 147. We expect that the improved proper motion precision will enhance our ability to determine the nature of unproven clusters like Lodén 1 and improve the membership identification of established clusters like Ruprecht 147.

Artist's impression of Gaia

Artist’s impression of Gaia

The stars that make up a cluster travel together through the galaxy, with little spread in position (e.g., clusters can span 10—20 light years) and velocity (typically 500 m/s, whereas the cluster itself can travel at tens of km/s relative to neighboring stars). Within a few years, Gaia will release 3D positions (coordinates and parallaxes) and 3D space motions (proper motions and radial velocities) for some 150 million stars, while fainter stars will still receive 3D positions and 2D proper motions. Even sparse star clusters like Ruprecht 147 are 2—3 times denser than the Solar neighborhood. This is not a huge contrast; however, the inclusion of ultra-high-precision proper motions from Gaia (which will see a 100—200x increase in precision over existing proper motions) will make finding sparse clusters easy!

Gaia’s measurements will let us….

  1. “Weigh” clusters by measuring velocity dispersion from proper motions
  2. Resolve internal structure of nearby clusters with parallaxes, and eliminate distance uncertainty for others
  3. Enable easy cluster identification by looking for over-densities in 5D phase space (3D positions—including parallax— and proper motions). Basically, stars are distributed throughout the Solar neighborhood and nearby galactic environment with a characteristic density or spacing. Clusters, even sparse clusters, should appear as over-densities given the expected high precision of the parallaxes. Furthermore, the stars in a given few parsec volume do not exhibit coherent proper motion. Together, these 5 position/motion components should yield new clusters, and new members of known clusters.

Lots to do, but first we should search for bound and moderately rich (N>20) systems that can immediately be characterized and targeted by space missions like TESS.

Our paper is now on the arXiv and will soon appear in the Astronomical Journal.

A Question for METI Critics

In a new paper (put putting forth an old argument) John Gertz argues that attempts to send deliberate signals for detection by alien civilizations is “unwise, unscientific, potentially catastrophic, and unethical.”  His rather caustic assault on METI-proponents is a pretty good summary of the extreme METI-opponent position. (METI = Messaging to ExtraTerrestrial Intelligences).

One thing that caught my eye that I had not heard before is that he obliquely proposes that something like an ethics review board weigh in on any powerful transmissions made by Earth.  He specifically mentions Arecibo radar pulses used to probe Solar System objects:

The asteroid detection radar problem is very easy to fix by adopting a standard of best practices that includes a provision for muting the radar during moments when the target occults a nearby star or transits the plane of the Milky Way.

The agent of our destruction?

The agent of our destruction?

I may be behind the times here, but this is the first time I’ve heard that the planetary science community should consider the ethical implications to the planet for their observations (as opposed to just the ethical implications of the deaths of any birds that happen to fly above the dish during transmission).

But Gertz interestingly does not mention laser AO programs, which send powerful laser beams to some of the nearest stars routinely.  Indeed, Kipping & Teachy recently showed how relatively powerful lasers from other worlds would be easily noticed as artificial signals even with our present technology, and searches for pulsed laser emission is one of the most promising SETI routes we have.  Tellis & Marcy have searched for lasers as weak as tens of Watts coming from tens of AU away from nearby stars.  I haven’t run the numbers, but it would surprise me if our laser AO systems, pointed right at nearby stars, were not detectable by an advanced alien civilization as being obviously artificial.

So my honest question to Gertz and other METI opponents is whether we should seriously be setting up review boards for laser AO and planetary radar?  What about the powerful arctic radars used to look for ICBMs that sweep across the sky? How powerful or coherent must a transmission be before we consider its ethical implications?

As a METI agnostic, I don’t have an answer to these questions; I’m genuinely curious to have this discussion.



Lodén 1, Part III: Neither Old, Nor Nearby, Nor a Cluster

Last time I described how the photometry of the stars in the purported cluster Lodén 1 didn’t seem to really implicate a cluster.

The next step was to get some radial velocities. Jason Curtis submitted a proposal to SALT—the South Africa Large Telescope—to use the Robert Stobie Spectrograph (RSS).  Lodén 1 is in the Southern Hemisphere, so we couldn’t use HET, but SALT is an HET clone, and in exchange for the plans and lessons learned on HET, the HET consortium, including Penn State, got institutional access to SALT for a few years.

The South Africa Large Telescope.

The South Africa Large Telescope.

The telescope was still working out its growing pains, so we never got all of the observations we asked for, and the reduction pipeline improved as we went along, but in the end we got some nice spectra of two classes of stars: Lodén’s original candidates, and the members identified by Kharchenko.

Eunkyu Han, now a graduate student at Boston University.

Eunkyu Han, now a graduate student at Boston University.

The reduction and analysis was done by Eunkyu Han, at the time a post-baccalaureate researcher for our group, and now a graduate student in Phil Muirhead’s group at Boston University.  Eunkyu did a lot of work reducing all of the data from SALT down to just the number we wanted: the radial velocity  Thanks a lot to the SALT staff for helping us with the reductions and wavelength solutions on this relatively new and untested instrument!

These medium resolution spectra measure radial velocities to a km/s or so.  This is enough to see if they’re all roughly the same (in the case of a co-moving group of stars in a cluster) or basically random (as we’d expect for field stars).  This is what they look like:

Medium-resolution spectrum of Lodén's candidate 5. All of this light is roughly in the orange portion of the spectrum, with yellow off the left hand side and deep red off the right hand side. The deep lines marked "Na D" are where the star is dark, exactly at the color of those orange sodium street lamps. This is due to sodium in the star's atmosphere. The inverse-Eiffel-Tower shape on the right is from hydrogen in the star's atmosphere. The difference in the wavelengths of these lines as we observe them and as they are in the lab tells us how fast the star is moving towards or away from us. We actually used the narrow lines marked in red to make this determination. (The blue line shows where the Earth's atmosphere messes with the measurements).

Medium-resolution spectrum of Lodén’s candidate 5.

All of this light is roughly in the orange portion of the spectrum, with yellow off the left hand side and deep red off the right hand side. The deep lines marked “Na D” are where the star is dark, exactly at the color of those orange sodium street lamps. This is due to sodium in the star’s atmosphere. The inverse-Eiffel-Tower shape on the right is from hydrogen in the star’s atmosphere. The difference in the wavelengths of these lines as we observe them and as they are in the lab tells us how fast the star is moving towards or away from us. We actually used the narrow lines marked in red to make this determination. (The blue line shows at which wavelengths the Earth’s atmosphere messes with the measurements—you can see why we avoided those regions!).

So, is there a cluster of stars all at the same velocity, distinct from “the field”?  Or does it look basically like you’d expect for random stars?  Here’s Eunkyu’s result (in black) and what we expect from a random collection of stars in that direction (from Jason Curtis):

Radial velocity distribution of candidate Lodén 1 members. Nothing to see here; move along…

Radial velocity distribution of candidate Lodén 1 members. Nothing to see here; move along…

Yeah, there’s not much there.  There is a peak, but it’s about where you expect to find one, anyway.  We plotted up the stars in that peak and found… nothing that looks like a coeval sequence in the photometry.


  • We looked at the colors of the stars, and found lots of A stars, so its not old.
  • We looked at a color magnitude diagram, and nothing stood out from the field, so if anything is there, it’s not bright, so it’s not nearby.
  • And looking at the motions of the stars, it’s exactly what you expect from the field.

In short, the old, nearby cluster Lodén 1 is neither old, nor nearby, nor a cluster.

Paging Linda Richman…

Paging Linda Richman…

So this one didn’t pan out, but, as we wrote in the paper, “The potential utility that would come with the discovery of a new 2 Gyr star cluster at a distance of only 360 pc was sufficiently high that it warranted careful inspection and disproof.”

We did get into a semantic argument with the referee about whether if there is any cluster or association in the field that Gaia might find, it would be Lodén 1 or not.  We decided not; your mileage may vary.

Next time: Final thoughts, and cluster hunting in the era of Gaia.


Lodén 1, Part II: Proving a Negative

Last time, I described how Jason Curtis proved that the long-forgotten cluster Ruprecht 147 was actually an important benchmark in stellar astrophysics.

We wanted to know if two other entries in WEBDA — Lodén 1 and NGC 2240 — might be similarly useful.

We were pretty skeptical.  Neither “cluster” has a proper motion that distinguishes it from the field.  This means that there is no indication that the stars in those overdensities on the sky are moving as a group—the only reason to think that there might be a cluster there is that there seem to be more bright stars in the region than one would expect by chance.  But it’s a big sky—chance has lots of opportunities to fool you.

Lodén 1 was first noticed by L. O. Lodén in 1980, in his search for “hidden” clusters in the southern galactic plane.  Lodén noted an “evident concentration of late-type stars…and main sequence A–F stars” whose physical association was “not confirmed by strongly suspected.”  Kharchenko’s 2005 analysis put the cluster at 175 pc and 2.5 billion years old— very useful if true, but somewhat inconsistent with Lodén’s note that the cluster contains A stars (though they could be blue stragglers, of course).  A later paper by the Kharchenko group put the cluster at 200 million years old and over 750 pc away, further confusing the issue.  We suspected that the reason the two fits came out so differently was that the Kharchenko algorithm was trying to fit field stars, and so had a GIGO problem.

Part of a figure from Eunkyu and Jason Curtis's paper

Part of a figure from Eunkyu and Jason Curtis’s paper showing color-magnitude diagrams for Lodén’s “field 1” and a control field at the same Galactic latitude.

Jason Curtis did a lot of work putting isochrones down on color-magnitude diagrams for stars in the field.  The above figure shows the Kharchenko et al. 2005 isochrones for the “cluster” in gray, and in red the same isochrone shifted out to 500 pc.  The left panel shows Lodén’s field 1 (the location of the purported cluster), and the right shows a nearby control field at the same Galactic latitude.

The right panel shows “field stars”— the colors (x-axis) and brightness (y-axis) of the random stars along this line of sight in the Galactic plane.  The red (high J-K) stars are mostly intrinsically bright, background K giants at a variety of distances (farther away makes you fainter, moving you down in the graph).  The blue stars (J-K near 0) are mostly hot, young stars randomly strewn along the line of sight.  There is no clustering along either isochrone line because there is no coeval cluster of stars in this region—if there were, you would expect to see an overdensity of points along those or some similar isochrone.

The left hand panel shows the Lodén 1 field, and you’d be hard pressed to tell it was any different from the control.  True, there are a few more bright stars: not really any more red giants, but there are 7–10 blue stars with J < 9.25 or so, while the control field only has 3.  Those are presumably the blue stars that caught Lodén’s attention in the first place.

For reference, here’s how Ruprecht 147 looks:

Color-magnitude diagrams for Ruprecht 147 and a control field.

Color-magnitude diagrams for Ruprecht 147 and a control field.

Its control field looks very different (it’s farther from the plane, so the field stars are typically more distant) but the cluster field has the unmistakable presence of a cluster: lots of stars on the Main Sequence, a healthy but smaller red giant branch population, and even a few blue stragglers (the bright blue stars off of the red line).

If you squint, you can try to make the Lodén 1 stars fall on the red line there, but the numbers are all wrong: given the number of giants, there are way too few Main Sequence stars for this to be real.  The control field actually has a more convincing coeval sequence.

So there doesn’t appear to be anything obvious here.  But that doesn’t mean that Lodén was wrong, just that the cluster doesn’t stand out very well from the field.  To really be sure, we need to see if there are any comoving stars in the field.  We can use catalog data to see in which direction on the sky the stars are moving, and see if there is a subset of them all going in the same direction.  Ruprecht 147 stands out nicely by this metric:

Proper motion diagram for Ruprecht 147

Proper motion diagrams for Ruprecht 147 field and control. Blue cross gives representative error bars.

Here the motions in the north and east directions are plotted ((0,0) is no motion) for all of the stars in the Ruprecht 147 field (left) and its control field (right).  The red circle marks the position in proper-motion space of the cluster.  The control field reveals that field stars generally have zero proper motion — this is because they are typically very distant, so they seem to move very slowly across the sky. The more nearby field stars have large proper motion (they are farther from (0,0)), but there aren’t very many of those, so there’s not much contamination in the red circle.  The cluster itself has a bunch of stars moving southward at a bit over 20 milliarcseconds per year; the overdensity is obvious in the figure above.

How about Lodén 1?

Lodén 1 proper motion diagram

Proper motion diagrams for Lodén 1 (left) and control field (right)

Yikes.  There is no obvious overdensity.  If this cluster is real, its is not moving significantly through the plane.

At the referee’s request, Jason Curtis did some heriocs trying to see if there was an overdensity buried in there, using the control field as a guide.  Noting convincing came out.

But these things are important if they’re real, and we should give some deference to Lodén’s intuition on this.  The real test would be to measure the two missing components to these stars’ motions and positions: their radial velocities and distances.  The distances will have to wait for Gaia, but the radial velocities we could do ourselves.

Next time: Eunkyu collects radial velocities, and pronounces her verdict.

Lodén 1, Part I: Finding new, nearby, old open clusters

Jason Curtis, soon to be an NSF postdoctoral fellow a Columbia University

Jason Curtis, soon to be an NSF postdoctoral fellow a Columbia University

Jason Curtis’s PhD thesis is on the “old”, nearby open cluster Ruprecht 147.  I first came across this cluster when naively looking for an “old” (> 1 billion years) open benchmark cluster to compare field stars with, as part of the GPI target selection group when I was a postdoc at Berkeley.

The cluster was listed in the online open cluster database WEBDA as being nearby (within 500 pc) and “old” (globular cluster astronomers would call it “intermediate aged”— 10 Gyr is old!).  This was based on work by Kharchenko et al. in 2005 who used “known” stellar associations’ proper motions to find new members (fitting their brightnesses and colors with stellar isochrones) and pin down their cluster parameters in a uniform way.  But they had not looked hard at Ruprecht 147 itself, and its fit seemed poor to me—the isochrone passed through the blue stragglers, for instance.

Distances and ages of clusters in WEBDA. The blue open circle is where I had found Ruprecht 147 (in the database) in 2007. The closed circle is Jason Curtis's value. What's that red point?

Distances and ages of clusters in WEBDA. The blue open circle is where I had found Ruprecht 147 (in the database) in 2007. The closed circle is Jason Curtis’s value. What’s that red point?

It turns out that prior to Kharchenko’s work, it wasn’t even clear than Ruprecht 147 was a real cluster.  Jason’s paper beautifully traces out the history here, but basically the overdensity of stars in Sagittarius that marks the cluster was noticed over 150 years ago by John Herschel, but not really believed to be anything other than an asterism by most observers since.  Jaroslav Ruprecht “rediscovered” the cluster about 50 years ago (accidentally giving it a new name), and both that entry and Herschel’s have been dutifully copied from catalog to catalog ever since.

After much work, Jason Curtis established that Kharchenko was absolutely correct that many stars in the area share a common proper motion: the cluster is real, truly nearby, and truly not young.  His refined cluster parameters (300 pc and 3Gyr) are reflected in the figure above (the blue “C13” point).  As you can see, Ruprecht 147 is superlatively old and nearby, much closer than M67 and much older than Praesepe, two critical benchmarks in stellar astrophysics.  With over 100 members, Ruprecht 147 is poised to become a similarly important object of study (which is one thing Jason will work on as an NSF postdoctoral fellow at Columbia University in Marcel Agüeros’s group).

Ruprecht 147 had escaped notice for so long because it sits in Sagittarius—one of the densest regions of stars in the sky—and because it is so close that its stars are scattered over many square degrees.  Its age also hurts it: all of its O, B, and A stars have long since evolved past the giant phase and are now gone or too faint to notice (the remaining 5 or 6 A stars are blue stragglers) so there are few bright stars to draw they eye’s attention like in Praesepe.  It was the Tycho proper motions that made it stand out to the point that Kharchenko’s algorithms proved it to be real.

That figure also shows two other objects, NGC 2240 and Lodén 1, that might be similarly important, if real.  What are they?  Could they be new benchmarks in stellar astrophysics?

Jason Curtis and I put former Penn State undergraduate (and, later, baccalaureate researcher) Eunkyu Han on the case, and her paper is now ready for publication.

More in the next installment

Twenty Years of Precise RVs III: What Keck Gave Us

Last time I wrote about my summary of the Lick Planet Search at the  at the OHP2015 conference; today I’ll finish up with what we learned from Keck.

In the mid-1990’s, Geoff and Paul were strengthening their connections to UC Berkeley, where with Gibor Basri they were using the Lick Observatory facilities.

Geoff and Paul in their UC Berkeley office circa 1994.

Geoff and Paul in their UC Berkeley office circa 1994.

Having connections via UC Santa Cruz and Berkeley, they were able to plan to extend their planet search to the new new HIRES spectrograph at Keck Observatory, which was, like the Lick Hamilton spectrograph, designed by Steve Vogt

Of course, HIRES was going to need an iodine cell; here are Geoff’s instructions to SFSU glass blower Mylan Healy for its construction.

Notes on the construction of the iodine cell for Keck for SFSU glass blower Mylan Healy.

Notes on the construction of the iodine cell for Keck for SFSU glass blower Mylan Healy.


Debra Fischer joined the team as a postdoc in 1997, a couple years before I arrived in 1999.  Here she is working to get a Fourier Transform Spectrograph scan of the Keck iodine cell:

Debra getting an FTS scan of the Keck iodine cell.

Debra getting an FTS scan of the Keck iodine cell.

HIRES proved to be capable of more precise velocities than the Hamilton, regularly achieving 1-3 m/s precision on stable stars.

One of the biggest benefits of a long survey is that you can detect loooooooooong period planets.  This culminated in a few significant discoveries I talked about at OHP: the 10th good Jupiter analog, announced by Sharon Wang (who is going to work with Paul in DC as a DTM Fellow this fall):

HD 37605 b and c, discovered with Keck and HET velocities.

HD 37605 b and c, discovered with Keck and HET velocities.

And many more such planets were announced by Katherina Feng (now a grad student at UCSC).  Here’s one some with large period ratios (the largest known between planets in a system — including in the solar system!)

HD 187123 b & c, which are the planets with the highest known well-measured period ratio

HD 187123 b & c, which are the planets with the highest known well-measured period ratio

I also had some comments about activity cycles, but I’ll save those for another post, another time.  If you’d like to learn more, my contribution to the conference proceedings is on the arXiv and on the OHP2015 site.

And there’s a link to video of my talk here.

Twenty Years of Precise RVs II: Early days at Lick

Last post I described the OHP2015 meeting in France, where I gave a talk.

My contribution to the conference proceedings just went live, and you can read them on the arXiv or on the OHP2015 site. For a “personal history” of the same material, told with greater authority and detail see Paul Butler’s post on the Pale Red Dot site.

The Lick Planet Search begin in the late ’80’s at the Shane 120-inch telescope on Mount Hamilton, in the mountains above San Jose (you can see the dome of the Great Refractor from the 101 freeway in San Jose).

The Shane 120-inch at Lick Observatory on Mount Hamilton, above San Jose. I spent many, many (too many) nights on that mountain in my many (too many) years in graduate school.

The Shane 120-inch at Lick Observatory on Mount Hamilton, above San Jose. I spent many, many (too many) nights on that mountain in my many (too many) years in graduate school.

The spectrograph lives in a basement room beneath the siderostat shed seen here. On nights when other instruments were in use (like those using the laser, seen here), the spectrograph could still be accessed with an auxiliary telescope.  The shed opens, and the siderostat reflects starlight up into the port in the side of the dome.  A small, 0.6 meter telescope is housed inside the dome, and feeds the spectrograph by sending light down into the slit room in the basement, where a pickoff mirror sends the light into the path normally used for light from the 3-meter.

View of the siderostat from the perspective of the port in the side of the dome. This mirror feeds the small "CAT": Coudé Auxiliary Telescope.

View of the siderostat from the perspective of the port in the side of the dome. This mirror feeds the small “CAT”: Coudé Auxiliary Telescope.


The work to extract precise RVs from the spectrograph was largely done at San Francisco State University by Geoff Marcy, Paul Butler, and their students and colleagues. The primary problem is that the instrument was not stable, and the “instrumental profile” or “line spread function” varied with temperature, pressure, position of its various components, and (trickiest of all) the illumination of the slit (which varies from exposure to exposure).  Working with Jeff Valenti at CU Boulder, Marcy & Butler determined that they could use the precisely known spectrum of the iodine lines (obtained at the McMath FTS in 1991) to determine the instrumental profile simultaneously with the velocity of the star by modeling the spectrum.  This was a significant computational burden at the time, but it worked.

Paul Butler at SFSU circa 1988

Paul Butler at SFSU circa 1988

The Doppler lab at SFSU. The wall is lined with diagnostic plots from the Lick Planet Search.

The Doppler lab at SFSU. The wall is lined with diagnostic plots from the Lick Planet Search.

The original cell was designed by Paul Butler and Geoff Marcy, and blown by SFSU glass blower Mylan Healy:

The original iodine cell for Lick.

The original iodine cell for Lick.

Paul Butler, a chemistry masters student at SFSU, tested many different compounds to replace hydrogen fluoride, the original gas used by Bruce Campbell and Gordon Walker to get below 20 m/s precision at DAO.  HF is notoriously dangerous to work with, and molecular iodine had been suggested by Robert Howard at the Carnegie Institution of Washington, inspired by work by Beckers in the late ’70s.  Similar work was also being done by Libberecht and Hatzes & Cochran.  Paul spent months trying many compounds many of them “explosive, deadly poisonous, or both” before settling on iodine.

Since pure iodine is a solid at STP, the gas cell is evacuated and heated to ensure complete sublimation of the small amount of iodine within.  The blue cylinder in the picture is thermal insulation, and the wires are for the temperature controller that kept the cell at constant temperature.  The arm held the cell in the path of the light.

Fancy picture of the iodine cell in position at Lick Observatory. I think that's Debra Fischer's hand. Image copyright Laurie Hatch, used with permission.

Fancy picture of the iodine cell in position at Lick Observatory. I think that’s Debra Fischer’s hand. The beam is shown bouncing off of the slit plate, behind which is the spectrograph room. Image copyright Laurie Hatch, used with permission.

Another technical hurdle was a spectrograph that delivered high resolution, a broad bandpass, and a high-quality, linear detector.  The Hamilton spectrograph fit the bill.  It was built (and later upgraded) by Steve Vogt (one of Geoff Marcy’s thesis advisers) seen here holding a spooky glowing orb of some kind 1.


Paul calls the Hamilton “arguably the first modern echelle spectrometer”.

The Lick Planet Search really took off within days of the announcement by Mayor & Queloz of the discovery of 51 Peg b.  Geoff and Paul immediately confirmed the discovery, devoting what little computing power they had access to to analyzing data just for that star from a single observing run. The ensuing attention gave them access to more computing power, and in short order they announced the next nine exoplanet discoveries (most already in their unanalyzed data!).

The Lick Planet Search spanned 25 years, and owes its success to almost innumerable observers (we tried to track down all their names and thank them in the acknowledgements here).  Of special note are Debra Fischer, who ran and improved the program for years, and John Johnson, who did his thesis using the Hamilton.

The Lick Planet Search was still producing until one fateful day that the temperature controller partially failed.  Unfortunately, the part that failed was the part that turned the heater off, and as a result the insulation was melted and the cell badly damaged.

The sad fate of the Lick iodine cell.

The sad fate of the Lick iodine cell.

My understanding is that Geoff Marcy donated the cell to the Smithsonian.

In total, the Lick Planet Search made 14,000 observations of 386 stars. Debra published the entire radial velocity archive in 2014, ensuring that its legacy will be maintained.

Next post: the planet search moves to Keck.


1 Yes, I know it’s a mirror.

Twenty Years of Precise RVs I: A meeting in France

In October of last year, a lot of exoplanet astronomers gathered in Observatoire de Haute-Provence (OHP), France, for OHP2015, a conference on “Twenty years of giant exoplanets”. Many thanks to SOC chair Isabelle Boisse, and LOC chair François Bouchy for their efforts putting it together.

For those who don’t know, OHP is where the field of exoplanetary astronomy got jump-started with the discovery of 51 Pegasi b by Michel Mayor and Didier Queloz using the ELODIE instrument (which we got to see when touring the facilities). Today, the same telescope uses the SOPHIE instrument to continue the precise RV tradition there.  The site itself reminded me a lot of Lick Observatory, actually (which is not too surprising; both are very near regions world-renowned for vineyards growing similar grapes).  bandeau_image_OHP_CNRS_900pxI had never been, and it was neat to get to travel to France and make minimal use of my high school French.  We stayed in the dormitories and got to visit a local fromagerie.

What I liked about the conference is that it focused on the first class of exoplanets discovered (pulsar planets aside), which is one that often gets forgotten when we focus on the (much more numerous) smaller and potentially terrestrial bodies being found by Kepler and at low amplitudes by RV.  These are the mature, presumably gas-giant planets orbiting at tenths to tens of AU from ordinary stars.

I was asked to talk about the 20 years of precise RVs at Lick and Keck observatories.  I started working with Geoff Marcy in 1999 or 2000, less than 5 years after the discovery of 51 Peg b, when there were still only a small number of exoplanets known.  I had heard enough stories from Geoff, Paul Butler, Debra Fischer, and Jeff Valenti, that I felt I could cover the territory pretty well.

So,I asked around and put together many slides of “vintage” photos showing things like the original Lick iodine cell and the lab at San Francisco State University where Marcy, Butler, and others got that planet search running.

I’ll blog about the content of my talk in future installments, but if you’re curious you can see my talk itself here:

Talk at OHP

Talk at OHP

I also recommend this “personal history” of the same material, told with greater authority and detail by Paul Butler on the Pale Red Dot site.

Next time: where it all started.

AAS Ethics Investigations

In a previous post I laid out my feedback to the AAS on its new draft Code of Ethics.  I’m glad the AAS is addressing this, and especially glad that they are engaging the membership to craft a strong code that will improve our society.

My second concern in that piece was that the new investigative and punitive powers this policy gives the AAS seemed in need of revision (for instance a single person appoints the entire committee)  I wrote that it would help to know that similar committees in allied field’s professional societies work well, and have restricted their most vigorous efforts to severe cases, held a sense of proportion in their actions, and acted primarily to protect the powerless.

To satisfy my curiosity, I checked some of astronomy’s allied fields’ professional societies to see if any have standing committees charged with investigating, adjudicating, and punishing ethical breaches, including sexual harassment.

I could not find any.  The American Physical Society and American Chemical Society don’t seem to have any bodies that handle adjudication of ethical breaches.  Indeed, the APS doesn’t seem to address non-scientific misconduct (like harassment) at all, having, at most, a statement on treatment of subordinates.  In contrast, I am proud that the AAS is leading on this.

The ACS has a more thorough ethics program, with a committee whose job is to educate and provide resources for the community.  I would like to see the AAS do this as well.

But in my quick search I couldn’t find any body at ACS responsible for investigations of wrongdoing (the Ethics Committee itself serves as a resource “but not as an adjudication body”.)

The American Geophysical Union’s Ethics Committee was the closest to an exception.  It provides an easy-to-find link for people to submit complaints of violations, and serves to investigate allegations.  Some features of this committee (and what I like about them in parentheses):

  • The chair of the committee determines which allegations to bring to the full committee (discretion to investigate)
  • The committee is composed of at least one member from committees responsible for outreach, meetings, and publications, and one AGU editor in chief, one editors, and one associate editor. Additional members can be added as appropriate for specific allegations (guaranteed broad representation and appropriate expertise on the committee)
  • Members are appointed by their respective committees, in consultation with AGU leadership (distribution of power)
  • It is not a standing committee; it convenes only as needed (it is not their job to go find work to do)
  • The committee’s recommendations at the end of an investigation go to the AGU board of directors, which decides punishment. (separation of powers)

I find many features of this setup appealing, and indeed many of them are in the current version of the Code of Ethics.  Of course, its possible that this model doesn’t work well, or is missing important features that would be important for the AAS to include. I encourage the AAS Ethics Task Force to contact the AGU (including those who have brought complaints to the AGU Ethics Committee) see how well it works, and to consider whether to adopt components of this model in the AAS Code of Ethics.

Whether they agree with me or not, I encourage all AAS members to give their feedback to the AAS here.

AAS Ethics Policy

The late unpleasantness in astronomy has rightly led the American Astronomical Society to take a new look at its ethics policy (here) which was adopted in its current form in 2010.  The current code lacks any enforcement mechanism, and so a new draft has been adopted that includes one (you can read it here).

I like the current version of the AAS Ethics Statement, but it is primarily aspirational.  I have three major concerns with the revised version.

My first concern is the following language, in the preamble:

Upon acceptance or renewal of AAS membership, all members will be asked to acknowledge that they have read this Code of Ethics and will strive to abide by these as an AAS member. (emphasis mine)

This bit about “striving to abide by these [sic]” is new, and problematic.  It takes what was an aspirational ethics statement and turns it into a code of ethics, and one that members must pledge to follow as a condition of renewing their membership.

Now, I understand that the AAS would like the statement to have some teeth so that it can sanction very bad actors, and I get that having members promise to follow a code gives the AAS a basis for admonishing and correcting bad behavior.

Now, if the code truly contained, as it states, “the minimal standards of ethical behavior relating to the profession” then this wouldn’t be a big problem, but there’s a lot more in there than that (and there always was — the “minimal standards” language is in the current ethics statement as well).

For instance, the ethics statement (and the new code) states that

Scientists should…promote equality of opportunity and treatment regardless of gender, race, ethnic and national origin, religion, age, marital status, sexual orientation, gender identity and expression, disabilities, veteran status, etc.

I’m fully behind this statement—I agree with it and I’m proud that my professional society has this as official policy.  But the Code of Ethics isn’t a policy statement of the society, it is a set of professional norms that the AAS wants all of its members to agree to when the renew their memberships.

I’m sure there are lots of astronomers who do not agree with the quoted statement (in deed, if not in word).  It’s one thing to require these astronomers to acknowledge that the AAS would like them to promote equality (as the current ethics statement does). It’s another to require it of them as a condition of membership, which is what the new language does.  Indeed, taken literally, members who do not promote such equality (by, say, doing nothing at all on the topic) are in violation of the code of ethics. 

My second concern is the new investigative and punitive powers this policy gives the AAS.  Under the new policy the AAS gets a Committee on Ethics that receives complaints, can investigate them, and can act on them with outcomes ranging from no action, to admonishment, to expulsion from the society.  All of the committee members are appointed by the AAS president.

I’d really like to know if this is modeled on a successful committee in some closely allied field’s professional society, or is this something new we’re trying in light of recent events? For instance, it does seem sub-optimal that the entire Committee on Ethics will be appointed by a single person (the president). After all, the president could be accused of a violation!

There have been (mostly anonymous) whisperings that the AAS is gearing up for a “witch hunt.” I find such whisperings to be rather paranoid (after all, the salient feature of a witch hunt is that, unlike unethical astronomers, witches don’t actually exist).  But this is not to say that a process of investigation and punishment cannot get out of hand or be abused. It would help to know that similar committees have restricted their best efforts to severe cases, held a sense of proportion in their actions, and acted primarily to protect the powerless.

My third concern is this language:

Any AAS member or meeting attendee who experiences or witnesses a violation of the AAS Code of Ethics should report that violation to the AAS Committee on Ethics.

I presume this is just poor drafting, but just to put a fine point on what’s wrong here: taken literally, this unqualified statement means that all members should report all violations of the code of ethics to the AAS that they “experience[] or witness[]”.  Combined with the language that led to my first concern, this implies that it is a requirement of membership to report event the most minor infractions (such as not promoting equality).  Yikes.

After all, what about people who are being harassed or abused and are fearful of retribution if they report? Or have trauma as a result? Are they in violation of the code of ethics if they don’t report their trauma to strangers at the AAS? Obviously they should not be, but if the language in this document seems to say that they are, then the language is far too broad.

To take another example of infractions that the AAS wants to know about:

“All people encountered in one’s professional life should be treated with respect. At no time is abusive, demeaning, humiliating or intimidating behavior acceptable“

As an aspirational platitude, that’s fine, which is why I’m OK with it in the current ethics statement.  As a professional norm that constitutes a basis for investigation and punishment, as in the new code of ethics, this is very problematic, because it’s not literally true.

To take just one example, if a junior member of our society is severely harassed (or worse) by a senior member, one can’t really expect that junior member to treat that senior member with respect. I can easily imagine situations where a junior member vents about the harassment on Twitter or some other public forum in impolite and unprofessional ways. The harasser could then point to the language of this document and report that the victim is violating the ethics code, and have them sanctioned! (Indeed, they have to report it!)


Again, I understand what the AAS is trying to do here, but trying to implement professional norms like this is hard and needs to be done carefully.  Imprecise language will lead to overly broad and so unenforceable rules, which will then be applied unevenly or not all.

We do need to have a hard conversation about ethics in our society and the AAS should be able to take action against bad actors.  I don’t think this current policy fits the bill.  It may be just a few tweaks before it’s in good shape; I’m not sure.

Whether they agree with me or not, I encourage all AAS members to give their feedback to the AAS here.

Mercedes Richards (1955-2016)

We are in mourning at PSU astronomy.  Our colleague Prof. Mercedes Richards died yesterday from complications of a chronic medical condition.

Mercedes Richards

Mercedes Richards. Image by Wendy Estep and Sara Brennen.

I first met Prof. Richards when I visited Penn State as prospective faculty. The interview was supposed to be about my exoplanet work, but we ended up talking about stars and stellar clusters.  After I was hired, it was always a pleasure to stop by her office for her thoughts on stellar activity, stellar evolution, spectroscopy, and teaching.  Her home in College Township is just a few doors down from ours, and the Richardses were always warm and welcoming neighbors.

Mercedes Tharam Davis was raised in Kingston, Jamaica, where her father, a police detective, and her mother, an accountant, taught her the power of deductive reasoning and care in one’s work.  She received her BSc in Physics from the University of the West Indies before moving to Toronto, where she earned her MSc (at York) and PhD (U Toronto) in astronomy.  She joined the faculty at the University of Virginia in 1987, and came to Penn State as a full Professor in 2002.

Prof. Richards is especially well known for her pioneering work in tomography of binary star systems and CVs.  By strutinizing spectroscopic and photometric time series of stars and compact objects in close orbit, Prof. Richards could create three-dimensional “movies” of mass-exchange systems, answering important questions about how mass transfer occurs.

Her research has been recognized with a Fullbright Distinguished Chair, and the Musgrave Medal.  The latter has been awarded occasionally by the Institute of Jamaica for over 100 years for achievement in art, science, or literature; Prof. Richards was just the 14th scientist to be so honored.

Prof. Richards’s service to the profession is exemplary.  She served as President of IAU Commission 42, a Councillor of the AAS, and organized numerous international conferences.  She served as our assistant department head from 2003-2008.

Prof. Richards’s dedication to students of all ages is well known.  Her introductory astronomy class was one of the most popular on campus.  She was a founder and director of SEECoS, a high school science outreach program of Penn State, and a Harlow Shapely Lecturer for the AAS.

I’m going to miss Dr. Richards; she has served as a role model educator, researcher, and scientist for me since my arrival.

Prof. Richards is survived by her husband Donald, who is a professor of statistics at Penn State and occasional co-author with her, and two daughters, Chandra and Suzanne.  They have always been joyful presences at department events, and our hearts and thoughts are with them today.

Oz in popular culture

Some spoilers for the Oz books below.

I’ve been reading the Oz books with my 5 year-old daughter, Georgia, before bed every night. I knew people called them classic American mythology, but I thought that was primarily based on the 1939 film, and a bit on The Wiz! and Wicked. I knew that the other books had many adaptations, but their cultural impact I thought must be small because I’d never seen or heard of their characters or plots.

Instead, what I’ve found is that, although clearly 100 years old, they have aged very well, and seem to have had broad and deep influence on popular culture beyond the first book’s adaptation in film.

We’re on the third book now, Ozma of Oz, and the number of popular culture echoes I’ve identified is already large. There is a strong theme of “animated people,” “talking animals,” and transformation in the books, but somehow each one that’s introduced seems fresh:

  •  Jack Pumpkinhead was the first one I noticed strongly—Jack the Pumpkin King from the Nightmare Before Christmas is clearly based on him.
  • The Tin Woodman’s origin in the books is very different than implied in the film. He’s not an animated statue—he’s a clumsy axeman who keeps amputating body parts, and having them replaced with tin ones, until nothing’s left; the transformation left him without any heart. He’s a cyborg that has lost his humanity. From the Skywalkers to countless cyborg films, this theme is now common in film.
    Jack Pumpkinhead with some familiar and less-familiar characters from Oz from The Marvelous Land of Oz
  • The “group of friends that heedlessly head into adventure and peril, and prevail through luck” storyline is used a lot. The books are serial, and there’s lots of unlikely coincidence and favorite characters meeting and teaming up to please fans of the books (as Baum admits in an author’s introduction). Baum probably didn’t start this, of course, but it’s a great and early example of the form in American popular culture that’s thriving today in this Golden Age of television.
  • Tiktok is a robot. Baum makes it clear he can think, has memory, is trustworthy and has empathy, but is not alive.  He’s a great exploration of what that could mean—in what sense is he not alive when the Tin Woodman is? Where modern characters like Data make this tension an explicit plot point, Baum prefers to simply assert the contradiction, like the droids in Star Wars.
  • The jolly but sinister Nome King and his nome army in his Underworld Kingdom is a direct ancestor of the dwarf (and goblin?) kingdoms of Middle Earth.  The description of the underworld halls read like they could have been the basis for Jackson’s film adaptations of LOTR.
  • I detected echoes of Princess Langwidere in the Fireys in Labyrinth, but she’s also a metaphor for moodiness and the inconstancy of personality.  The theme of trying on someone else’s personality and/or face is another cinema favorite.
  • Unlike the film version with her “mid-Atlantic” accent, the book version of Dorothy is a hick, a Mark Twain-ian noble uneducated rural American. She’s got a great line about why, unlike the haughty Princess Ozma, she’s not too proud to beg for an audience with the Nome King: “I’m only a little girl from Kansas, and we’ve got more dignity at home than we know what to do with.”
  • The Gump is basically a zombie, a reanimated monster from found parts. He’s clearly based on Frankenstein’s monster, but with full memory and faculties from his old life.  At the end of the book he begs to be disassembled because he’s an unnatural abomination. A great example of how Baum can explore some pretty dark themes with a cheery tone.
  • The brainless but wise and faithful Scarecrow seems to me an echo of Sancho Panza.  A similar character from another American myth is Jar Jar Binks; Julia suggests Inspector Gadget as another.
  • The idea for the Hungry Tiger is brilliant, but I can’t think of any similar characters since.  He’s a bloodthirty predator with morals.  He’s always growling threateningly about how hungry he is, how much he wants to eat the other characters, how much he’d love to find a fat baby to devour.  But he knows that it would do no good—eventually he’d get hungry again, and then he’d be responsible for a needless, innocent death.  So he’s always hungry.  This isn’t really Baum moralizing—the Cowardly Lion happily, regularly heads into the forest to find dinner.  This is sort of like the “reformed vampire” trope, except that the rationale is different: the Hungry Tiger would gladly take a life to permanently satisfy his hunger.

In some ways, the mores of the Oz books were ahead of their time.

  • For instance, there is a lot of gender-bending.  There’s a hen named “Bill” because she was misgendered as a chick (Dorothy calls her “Billina” because “Putting the ‘eena‘ on the end makes it a girl’s name, you see”). And there’s even a sex-change of a major character I can’t write more about without major spoilers (can you spoil a 100 year-old classic American myth?)
  • Oz is basically ruled by women:
    • The witches ruling the cardinal kingdoms of Oz at the opening of the books are all women.  When we finally see another “fairy land”, Ev, we find it is ruled by the feckless Princess Langwidere.
    • In the second book, General Jinjur leads her army of women (volunteers recruited from all four cardinal kingdoms) to depose the Scarecrow from the Emerald City (recall the Wizard installs the scarecrow as his successor before departing in his balloon). She’s basically a feminist Social Justice Warrior out to overthrow the unjust patriarchy, and she briefly succeeds!

General Jinjur’s army conquers the Emerald City, deposing the Scarecrow

In other ways, there’s a lot of retrograde material:

  • Slavery is a thing, explicitly.  Our heroes chastise the Nome King for having (human!) slaves, but among their number are Tiktok and the Saw Horse, both of whom obediently and happily serve the “masters” that animated them.
  • General Jinjur’s army of women is incompetent because of their femininity— they’re armed only with knitting needles and motivated primarily by the prospect of raiding the Emerald City for gemstones to make jewelry with.
  • Men are always the muscle.
  • For an American classic, democratic principles are surprisingly absent. Rule by birthright is the norm, with the occasional usurper by force or trickery (the Wizard, General Jinjur).

OK, what modern influences from Oz have I missed?  I haven’t finished Ozma of Oz yet, so please don’t give any major spoilers in the comments if you’ve read past me, but go ahead and name characters I haven’t met.

AstroWright Group Science at #AAS227

AAS 227

It’s that time of year again! I’m not there at AAS myself, but here is some of the science I’m involved in to some degree.  Put them on your schedule with the AAS meeting app!

Tuesday oral, 10am, Sun D:

fabienne105.02 PSU Hubble Fellow Fabienne Bastien on using “flicker” to derive stellar gravities (and, so, masses) from Kepler and K2 light curves.  10am in Sun D.

Screen Shot 2013-11-06 at 9.38.47 AM.pngimage_normal.png 105.03 Right after Fabienne(!), NSF Graduate Fellow Jason Curtis (@jcwaalaaa) talks on what’s up with Ruprecht 147, the closest intermediate-age open cluster (a crucial test for gyrochronology!).  10am in Sun D. Stellar astronomers: Jason is on the job market this year.

Tuesday poster:

mccrady137.14 MINERVAn Nate McCrady (@natemccrady) presents all the latest science with Project MINERVA in the poster session.

Brendan138.26 Atmospheric escape and star-planet interactions in hot Jupiters: Brendan Miller (@brendanpmiller) presents new Chandra observations of HD 97658 and HAT-P-11 in the poster session.

Rachel Worth 138.30  PSU grad student Rachel Worth (@RachelJWorth) has results on Proxima Centauri’s Influence on Planet Formation in Alpha Centauri.  While you’re at her poster, ask her about lithopanspermia.  Dynamicists and astrobiologists: Rachel is on the job market this year.

Wednesday oral 2pm Sun D:

HgmRH_IK 220.03D Sharon (Xuesong) Wang (@sharonxuesong) gives her dissertation talk on solving the precise radial velocity issues at Keck and HET observatories. If you ever wondered about the nitty gritty of how precise iodine RVs are made, this is the talk for you.  Observational exoplaneteers: Sharon is on the job market this year!

Wednesday posters:

Julia Kregenow 245.08 Penn State teaches more undergraduates astronomy than any college in the country, including lots of Web courses.  How much do the students in those Web courses learn?  More than you think (as long as it’s done right.)  Julia Kregenow on how to keep learning gains high in Web instruction (spoiler alert: MOOCs aren’t doing it right).

Kim Cartier 250.03 A meta-poster! Kimberly Cartier (@AstroKimCartier) gives important advice on good poster design — in poster form!

Thursday oral 10am Osceola B:

Kim Cartier 306.06 Kimberly Cartier again!  This time talking about near-IR spectroscopy of WASP-103b at secondary eclipse, work she is doing with Ming Zhao and Thomas Beatty.

Friday oral 2pm Osceola 4:

Sam Halverson427.01D Finally, fans of fiber optic radial velocity work should not miss Sam Halverson’s dissertation talk on photonic systems for high precision radial velocity measurements, in particular his novel use of ball scramblers for very high scrambling gains at high efficiency.  Instrumentalists: Sam is on the job market this year!