Fourth day of the DPS meeting, and I found myself sitting through some great plenary talks.

cvprxvsvuaeikj1First up was Kleomenis Tsiganis‘s Farinella Prize lecture “Flavors of Chaos”, a rapid-fire tour of the intricate and complex web of gravitational interactions among planets and asteroids in our solar system.

Tsiganis’s described how, using a combination of computational and pencil-and-paper techniques, we can pick at the threads in this cosmic network to tease out the early history and evolution of our solar system.

For instance, the orbits of asteroids in the asteroid belt provide subtle clues that, billions of years ago, Jupiter moved inward almost to the orbit of Mars before backing out near to its current orbit, a celestial maneuver referred to as “The Grand Tack“.

cvpbr0kusaaqdlgThis presentation was followed by Leigh Fletcher‘s Urey Prize talk about the menagerie of seasonal changes we observe in the atmospheres for all the outer planets, from Jupiter to Neptune.

The talk was full of beautiful images of the roiling and boiling of planetary atmospheres and concluded with Fletcher’s plea to send another mission to the Uranus or Neptune before he’s too old to participate (some plans from NASA have a mission launching to Uranus or Neptune sometime in the late 2020s/mid-2030s).

Finally, we had a tag-team talk from Ashwin Vasaveda and Sanjeev Gupta about new results from Mars Curiosity rover. In addition to the stupefying images, the thing that impressed me most about the talk was just the level of detail to which we can infer the geological history of Gale Crater, where Curiosity landed.

cvpm7vnuiaarkpeGupta described how the tilt of beds of sedimentary rock could be used to infer the presence of a river delta spilling out into the crater, which suggests the existence of a long-lived (millions of years) lake in the crater, probably billions of years ago when Mars was warmer and wetter.


Animation showing how a machine-learning algorithm decides where lies the boundary between two classes of objects.

Third day of the DPS Meeting was full of fascinating talks about the orbital architectures of exoplanet systems.

One that caught my attention was Dan Tamayo‘s talk on using machine-learning to classify the stability of a planetary system.

As astronomers have discovered more potential planetary systems, it’s becoming more time-consuming to decide whether what we see are actually planets or some other thing that has fooled us into thinking they’re planets.

When astronomers find what they think might be a planetary system, one of the first things they check is whether the putative planetary system is actually stable — that is, whether the gravitational tugs among the putative planets would cause the objects to crash into one another or be thrown out of the system.

Since most of the planetary systems we find are probably billions of years, astronomers expect that real planetary systems are stable for billions of years, so if the system we’re looking out turns out to be unstable on short timescales (less than billions of years), we usually decide that it’s not really a planetary system (or that we mis-estimated the planetary parameters).

Unfortunately, doing this check usually requires running big, complicated computer codes, called N-body simulations (“N” for the number of planets or bodies in the system) for hundreds or thousands of computer-hours. That can be a problem if you’ve got planetary candidates flooding in, as with the Kepler or upcoming TESS missions.

Tamayo wanted to try a different approach: what if the same machine-learning techniques that allow Google or Facebook to decide whether someone is likely to buy an iPhone could be used to more quickly decide whether a putative planetary system was stable

So Tamayo created many, many synthetic planetary systems, some stable, some not, and had his machine-learning algorithm sort through them. According to Tamayo, his scheme was able to pick up on subtle features that helped distinguish stable systems from unstable ones with very high accuracy in a fraction of the time it would take to run an N-body simulation.

aaeaaqaaaaaaaamaaaaajdjmowm5yzjjlwjhzgitnge4ys05ogi3lwu4mdjmmmi4zgexyqI also attended an eye-opening talk from Patricia Knezek of NSF about unconscious biases and their effects in astronomy and planetary science. Knezek explained that several studies have shown how these biases cause everyone to draw unconscious conclusions about someone based on very cursory information, such as their first name, race, gender, etc.

For instance, one study showed that the same application for a faculty position did much better if the applicant’s first name was “Brian” instead of “Karen”, even when women were evaluating the application.

Fortunately, these same studies have shown several ways to mitigate the effects of these biases, and being aware of them is a big first step.

What hot Jupiters might look like for a range of atmospheric temperatures. From

What hot Jupiters might look like for a range of atmospheric temperatures. From

Second day of DPS, and I enjoyed several fascinating sessions on exoplanet atmospheres. One of the most visually appealing talks was given by Vivian Parmentier, a planetary scientist at the Lunar and Planetary Lab.

Parmentier talked about clouds in the atmospheres of hot Jupiters, gas giant planets similar in composition and structure to Jupiter but much closer to their host stars than Mercury is to our Sun. Because they’re so close to their stars, hot Jupiters are … well … very hot, with temperatures reaching thousands of degrees.

These very high temperatures probably mean that the atmospheres contain clouds made of some exotic condensables, such as iron, cromium, or even ruby.

In his talk, Parmentier explained that understanding what kinds of clouds might form in these atmospheres is important for interpreting the growing collection of  spectra collected using the Hubble and Spitzer Space Telescopes. He also showed a beautiful photo album, realistically depicting the appearances of hot Jupiters for a range of atmospheric conditions.

A detailed, if nuanced, story is emerging from these data, suggesting hot Jupiters have highly dynamic meteorology with chemically complex clouds.

I attended the Women in Planetary Science Discussion Hour, at which we addressed several issues confronting the planetary science community when it comes to expanding diversity in the field. Several planetary scientists have conducted recent studies revealing the current state of the field (e.g., the fraction of women involved in space missions has not kept pace with the fraction of women in planetary science overall).

These studies have also pointed out ways to expand our pool of talented scientists, including ways to improve faculty searches to make sure the people standing at the front of the classroom resemble more closely the people sitting behind the desks. The Women in Planetary Science blog gives a lot of relevant resources.

A plexiglass replica of Voyager's golden record.

A plexiglass replica of Voyager’s golden record by Steve Vance and others.

The first day of the DPS meeting was wall-to-wall with science. There were several talks about exoplanets or planets outside of our solar system, and at least one stuck out especially to me.

Christopher Spaulding of Caltech discussed the so-called “Kepler Dichotomy“. This cryptic phrase refers to a strange finding from the Kepler Mission.

Kepler discovers planets using the transit technique (i.e., by looking for a planet’s shadow as the planet passes in front of its star), and so we expect only to find a small fraction of planets in our galaxy this way since it’s unlikely for a planet’s orbit to be aligned just right for a transit.

In fact, Kepler found lots of systems in which several planets transit. By looking at these systems, we can estimate how many systems should have just one planet that we can see transiting. When we do, it turns out that Kepler discovered lots more such single planets that we would expect.

This result has led some astronomers to suggest that these singly-transiting systems might have formed in a different (“dichotomous”) way from the multi-transiting systems. Instead, Spaulding suggested that culprit behind this planetary mystery was the host star.

In his talk, Spaulding pointed out that, during their youths, these stars spun fast enough that they bulged out at their equators. These equatorial bulges tugged gravitationally on their planets, causing the orbits of planets closest to the stars to re-align and leaving the orbits of planets farther away alone.

The closest planets just happen to transit, but, because the orbits of their sibling planets are aligned differently, we just can’t see them via transit. Like a lot of exoplanet research, Spaulding’s work shows that planetary systems, especially in their youth, can be dynamic, even violent, places for planets to grow up in, far from the clockwork universe Newton envisioned.

Quilling moon by Jen Grier (@grierja).

Quilling moon by Jen Grier (@grierja).

In addition to science talks, the DPS meeting has begun hosting an astronomy art show. The same folks who collect planetary spectra and analyze photometric light curves also make some beautiful art, and one of the neatest works on display was a quilling (rolled paper art) image of the lunar surface.


I’m in beautiful (if not, totally sunny) California this week for the American Astronomical Society’s Division of Planetary Sciences annual meeting.

Before the meeting officially starts on Monday, I helped organize the DPS Educators’ Workshop, a DPS tradition where planetary science-types work with local school teachers to explain the most recent science and help them develop lesson plans and activities for their students.

We spent several hours with teachers from all over SoCal and discussed lots of great activities, but one of the most popular and visually appealing is the Art and Astronomy activity.

For this activity, we invite the teachers to recreate space-based images of planetary surfaces using pastels. As usual with this activity, the teachers at first demured but ended up creating stunning and vibrant images of craters, geysers, and river deltas.




The weather was up and down all day yesterday, but by the evening, the scattered clouds had completely disappeared, giving us a warm, clear to talk about the OSIRIS-REx mission and do some star-gazing.

The evening started off with a brilliant presentation from Alessondra Springmann, LPL grad student and scientist on the mission. I’ve included a youtube video of her presentation below.

After the talk, we looked at the Moon, Mars, and Saturn through the Physics Dept.‘s telescopes.

Thanks especially to our student volunteers. This wonderful event would not have been possible without their help.

Today, I was fortunate to be invited to present at an Idaho-wide teacher conference, “Learning Across All Dimensions“. I talked about how to view the upcoming solar eclipse on August 21, 2017.

I’ve posted my presentation below and provided a form through which folks can sign up to receive e-mail announcements about public astronomy events hosted by Boise State.

At journal club today, we discussed a recent paper in Nature from Tanguy Bertrand and François Forget that looks at how the topography and meteorology of Pluto conspire to produce the dramatic frosts and glaciers seen on the surface of Pluto during the recent New Horizons fly-by.

One of the most spectacular results from the fly-by was the discovery that Pluto has rugged mountain chains, enormous geographic basins, and flowing glaciers. The image below shows the evidence for glacial flow in Sputnik Planum, called the Heart of Pluto.

It had been suggested that the flowing nitrogen frost might have collected in Sputnik Planum from a source region connected to Pluto’s deep interior.

However, coupling a sophisticated meteorological model to a model for vaporization and condensation, Bertrand and Forget show in their study that the gathering of frost in Sputnik is likely just due to the fact that it’s a deep basin, about 4 km below the Plutoid.

As a result, the atmospheric pressure tends to be larger at the bottom of the basin than elsewhere on Pluto’s surface, which encourages frost deposition there. The authors point to a similar effect on Mars, where CO2 snows out preferentially at the south pole in Hellas Basin.

It’s worth keeping in mind that the atmospheric pressure at Pluto’s surface is one one-hundred-thousandth the pressure at Earth’s surface, but even with a dwarf atmosphere, this dwarf planet exhibits complex and fascinating meteorological and geological phenomena.

And just because it’s awesome, here’s a synthetic fly-over of Pluto’s surface, generated by the New Horizons mission.

osiris-rex_artists_conceptionNASA’s OSIRIS-REx asteroid sample return mission launched on September 8th to visit asteroid Bennu, a carbon-rich, near-Earth asteroid. The spacecraft will rendezvous with the asteroid in 2018 and ultimately bring samples of Bennu back to Earth in 2023. Join the Boise State Physics Department on Oct 7 at 7:30p to celebrate the launch.

The event will kick off at 7:30p in room 101 of the Multipurpose Classroom Building on Boise State’s campus, right across the street from the Brady Street Parking Garage. Alessondra Springmann, a planetary scientist at the University of Arizona, will give a public talk on the OSIRIS-REx Mission.

At 8:30p, the event will move to the top of the Brady Garage, where telescopes will be set up for gazing at the Moon, Mars, and Saturn.

For more info, or e-mail Prof. Brian Jackson (

Flux time series for Boyajian's star, showing the 4-year Kepler observations. From Boyajian et al. (2016).

Flux time series for Boyajian’s star, showing the 4-year Kepler observations. From Boyajian et al. (2016).

At journal club today, we discussed a recent study from Jason Wright and Steinn Sigurdsson at PSU astronomy on a strangely dimming star observed by the Kepler mission.

The star has been called the WTF star (‘Where’s the Flux?’), Tabby’s Star (and probably a few more colorful things by perplexed astronomers), but Wright and Sigurdsson invoke the long astronomical tradition of naming noteworthy stars with their discoverers’ last names — they call it Boyajian’s Star, after Dr. Tabetha Boyajian, astronomer royale at Yale.

The strange thing about Boyajian’s star is that the Kepler mission observed the star to dim dramatically several times over a few years, dropping by 20% over the course of a few days several times over a few hundred days. That would be like having a partial solar eclipse that lasted 96 hours every few months. Even stranger, recent analyses of 100+ year old photographic plates suggest the star has been dimming, unnoticed, for a long time.

Various explanations for this strange behavior have been proposed, from enormous swarms of comets obscuring the star to alien megastructures, and Wright does a very good job exploring the different possibilities on his blog.

But as usually happens in astronomy, the most exciting explanations are the least likely (probably not an alien Dyson sphere), and Wright and Sigurdsson favor the idea that some sort of interstellar material between the Earth and Boyajian’s star is obscuring the star. Wright and Sigurdsson point out that, by measuring the distance to the star, the Gaia mission will help us resolve the mystery.