Twelve multi-planet systems where the innermost member is very close to the host star, that is, has an orbital period less than 1 day. From Adams et al. (2016).
Big research news today: our research group SuPerPiG, led by the inimitable Dr. Elisabeth Adams, announced the discovery of two new planets, EPIC 220674823 b and c.
Using data from the K2 Mission, we found these planets by looking for the shadows of the planets as they passed in front of their host stars, a planet-hunting technique known as the transit method.
These new planets are very different from planets in our solar system in several surprising ways.
First, they’re both bigger than Earth but smaller than Neptune – planet b is 50% larger, and planet c is 2.5 times larger. They inhabit a strange nether-region of planets where they’re known as super-Earths or sub-Neptunes, planets somewhere between Earth and Neptune. The reason there’s no specific name for such planets is because astronomers don’t understand this new class of planet at all.
An artist’s conception of CoRoT-7 b, another ultra-short-period planet.
Second, both planets are MUCH closer to their Sun than the planets in our solar system. In fact, planet b is so close to its sun that it takes less time to orbit (14 hours) than all the playtime it took the Cubs to go from 3 games down to tying up the World Series. By comparison, planet c circles at the glacial pace of once every 13 days.
Another thing that’s interesting about our planets: they’re yet another system of with an ultra-short-period planet (USP) in which there is more than one planet, i.e. a multi-planet system. In fact, as we argue in our paper, most of the known systems with ultra-short-period planets are probably multi-planet systems and that fact might help explain the origin of these chthonic planets.
Had a wonderful visit to London, Ontario last week, home of the University of Western Ontario. Weather wasn’t quite as nice as here in Boise, but the city was just as beautiful.
My friend and colleague Catherine Neish arranged for me to give three talks while there — one on our crowd-funding effort, one on my exoplanet research, and one on our dust devil work.
I’ve posted two of the talks and abbreviated abstracts below. The dust devil talk, “Summoning Devils in the Desert”, is a reprise of a previous talk, so I didn’t include it below.
Crowdfunding To Support University Research and Public Outreach
In this presentation, I discussed my own crowdfunding project to support the rehabilitation of Boise State’s on-campus observatory. As the first project launched on PonyUp, it was an enormous success — we met our original donation goal of $8k just two weeks into the four-week campaign and so upped the goal to $10k, which we achieved two weeks later. In addition to the very gratifying monetary support of the broader Boise community, we received personal stories from many of our donors about their connections to Boise State and the observatory. I’ll talk about our approach to social and traditional media platforms and discuss how we leveraged an unlikely cosmic syzygy to boost the campaign.
On the Edge: Exoplanets with Orbital Periods Shorter Than a Peter Jackson Movie
In this presentation, I discussed the work of our Short-Period Planets Group (SuPerPiG), focused on finding and understanding this surprising new class of exoplanets. We are sifting data from the reincarnated Kepler Mission, K2, to search for additional short-period planets and have found several new candidates. We are also modeling the tidal decay and disruption of close-in gaseous planets to determine how we could identify their remnants, and preliminary results suggest the cores have a distinctive mass-period relationship that may be apparent in the observed population. Whatever their origins, short-period planets are particularly amenable to discovery and detailed follow-up by ongoing and future surveys, including the TESS mission.
UPDATE (2016 Mar 24): The paper is now available for free on astro-ph.
The Astrophysical Journal published today a paper by my colleagues and myself investigating in detail a way to look for moons around transiting exoplanets.
The discoveries of thousands of planets and planetary candidates over the last few decades has motivated a parallel effort to find exomoons. In addition to providing a base of operations for the Empire, exomoons might actually be a better place to find extrasolar life than exoplanets in some ways.
This technique for finding exomoons, called the Orbital Sampling Effect, was developed by René Heller and involves looking for the subtle signature of a moon’s shadow alongside the shadow of its transiting planet host, as depicted in the image below.
The dark cloud shown around the planet represents the exomoon’s shadow, averaged over several orbits. At epoch (1), a satellite transits just before the planet. At epoch (2), the planet’s transit begins, inducing a large dip in the measured stellar brightness. At epoch (3), the satellite modifies the planet’s transit light curve slightly but measurably.
This simple technique has advantages over alternative exomoon searches in that it doesn’t require significant computational resources to implement. It can also use data already available from the Kepler and K2 missions. However, on its own, the technique can’t provide a moon’s mass, only its size, and it requires many transits of the host planet to find the moon’s quite subtle transit signature.
No exomoon has been found yet in spite of tremendous efforts to find them, so the search continues.
Artist’s conception of cloudy GJ 1214 b. From http://www.nytimes.com/2014/01/07/science/space/the-forecast-on-gj-1214b-extremely-cloudy.html.
At journal club this week, we discussed the recent discovery using data from the K2 mission of the sub-Neptune planet K2-28.
This planet, roughly twice the size of Earth, circles a very small M-dwarf star so closely that it only takes two days to complete one orbit. Even though the planet is very close to its star, the star is so cool (3000 K) and so small (30% the size of our Sun) that the planet’s temperature is only 600 K. (A planet in a similar orbit around our Sun would be 1200 K.)
The authors of the discovery paper point out that this planet is similar in many ways to another famous planet, GJ 1214 b. Like GJ 1214 b, K2-28 b is member of this puzzling but ubiquitous class of sub-Neptune planets — planets that fall somewhere between the Earth and Neptune in size and composition and do not exist in our solar system*. Both planets also orbit relatively nearby M-dwarfs, which means, like GJ 1214 b, K2-28 b might be amenable to follow-up observations.
Previous follow-up observations of GJ 1214 b indicated that planet’s atmosphere is very cloudy or hazy. So K2-28 b could provide another very important toehold along the road toward understanding this strange class of hybrid planet.
*unless Planet Nine turns out to be real
The red dots show the observations from this study, with the dips due to asteroid chunks transiting the white dwarf. The inset shows an artist’s conception of the disruption process.
For our second journal club meeting this semester (didn’t manage to blog the first one), we discussed a study from Saul Rappaport and colleagues on observations of the white dwarf WD 1145+017, which continues to show evidence that it is eating a small asteroid.
A study last year from Vanderburg and colleagues (which we discussed last semester) presented observations from the K2 Mission showing distinctive but highly-variable transit signals coming from WD 1145+017. That group conducted follow-up observations that pointed to the presence of an asteroid very close to the star, being ripped apart by the star’s gravity.
As crazy as it sounds, the idea that some white dwarfs are eating asteroids is fairly well-established, but Vanderburg’s study was the first to present observations of the process clearly in action. The variability of the transit signals indicates that the violent process is dynamic and complicated.
This new study from Rappaport and colleagues continues the saga of WD 1145+017 and finds that the disruption process persists more than a year after the initial observations. And using the apparent drift rates of the different chunks of asteroid, Rappaport is able to constrain the mass of the parent asteroid to be about 1% that of Ceres in our solar system.
One of the most exciting aspects of this study for me is that the observations were made using a network of small, amateur telescopes. Some of the scopes used in the study were 25-cm, and so I’m hopeful that, in the near future, we will be able to use Boise State’s own Challis Observatory to conduct follow-up. Just gotta wait for a clear night.
We had our last research group meeting of 2015 on Friday since finals are coming up soon. Fairly large crowd, though, for a meeting so late in the year.
Artist’s conception of Vanderburg’s disintegrating body. From https://www.cfa.harvard.edu/~avanderb/page1.html.
We discussed Andrew Vanderburg’s discovery of a disintegrating minor body orbiting a white dwarf star. The body, as small as Ceres or smaller, is so close to its host star that it’s actively evaporating and falling apart, and the shadows of the resulting dust cloud is visible data from the K2 Mission. The dust then falls onto the white dwarf, polluting its atmosphere in a way we can see spectrally.
We also had a very impressive presentation from Hari Gopalakrishnan of Renaissance High School on a recent study from Jim Fuller at Caltech. Fuller and colleauges analyzed oscillations at the surface of a red giant star to infer the presence and strength of magnetic fields deep in the star’s interior. Hari kindly shared the presentation, which I’ve linked below.
Attendees at this journal club included Jennifer Briggs, Karan Davis, Emily Jensen, Tyler Gordon, Steven Kreyche, Jake Soares, and Hari Gopalakrishnan.
We had an abbreviated research group meeting today at which we discussed the recent K2 Science Conference before I head off to the DPS conference in Washington DC. Everyone was in good spirits, considering how late in the semester it is. We’re planning to meet once more before Thanksgiving and will probably go on hiatus until spring semester after that.
Today’s attendees included Hari Gopalakrishnan, Jennifer Briggs, Emily Jensen, Karan Davis, Tyler Gordon, Jake Soares, and Steven Kreyche.
On my way back to Boise from the first K2 Science Conference, a week-long conference on the K2 Mission, successor to the Kepler mission.
Although I had to leave only two days into the conference (gotta get back to teach about the Origins of Earth Life), I got to see some amazing talks.
Talks that really stick out in my mind include Natalie Batalha‘s talk about the frequency of Earth-like planets (one for every three Sun-like stars); Roberto Sanchis-Ojeda‘s talk on a disintegrating planet with a cometary tail; and Jim Fuller‘s talk about measuring magnetic fields deep in the hearts of red giant stars by studying waves on the stars’ surfaces. The burritos at Sandbar on State St. are also pretty amazing.
All in all, a dazzling conference in refreshing Santa Barbara, CA.
I’m gearing up for the K2 Science Conference next week and preparing my presentation. So this week at journal club, I thought it would be fun for everyone to give short presentations on their research projects.
Jennifer Briggs talked about looking at secondary eclipses of the hot Jupiter HAT-P-7 b and how we’re trying to use variations in the eclipses to look for meteorological variability.
I presented some preliminary results from our SuPerPiG search for very short-period exoplanets using data from the K2 mission. The practice talk was very helpful to me because I learned that I had way too many slides.
We spent a little time talking about good presentation style and techniques, and it reminded me that Emily Lakdawalla of the Planetary Society put together a very good blog post about how to give a presentation.
This week’s attendees included Jennifer Briggs, Emily Jensen, Karan Davis, Tyler Gordon, Hari Gopalakrishnan, Ahn Hyung, and Jake and Steven (whose last names I still don’t know).
On Friday, everyone in our research group gave a little update on what they’ve been up to.
Liz and Jennifer talked about Parmentier et al.’s (2013) paper on the meteorology of hot Jupiters and how condensates are transported throughout these dynamic atmospheres.
Emily talked about working through the first few chapters of Murray & Dermott’s classic Solar System Dynamics. She will eventually study the orbital dynamics of systems of exoplanets very close to their host stars.
Brenton discussed his reading of Balme & Greeley (2006) on dust devils in preparation for working with me on terrestrial and Martian dust devils. A very exciting possibility, Brenton and the rest of the group said dust devils are common just south of Boise. Good chance we can do some in-situ monitoring locally.
Nathan spoke briefly about looking for more very short-period planets using data from the Kepler and K2 missions.
In attendance were Liz Kandziolka, Jennifer Briggs, Emily Jensen, Brenton Peck, Nathan Grigsby, Trent Garrett, and Tiffany Watkins.