Simulated dust tails around the disintegrating planet EPIC 201637175 b. From Sanchis-Ojeda+ (2015).

Fun research group meeting today. We discussed research papers on a new class of extrasolar planet, ultra-short period planets. Most of these planets are small and rocky, and some of them are so small, rocky, and hot that they are actively disintegrating.

We first discussed Spitzer Space Telescope observations by Demory and colleagues of 55 Cnc e, a rocky planet with a mass and radius eight and two times the Earth’s, respectively, but almost 100 times closer to its star than the Earth is to the Sun. Its surface temperature is about 2000 K, hot enough to form a molten rock lake on the planet’s dayside.

Demory and colleagues looked at 55 Cnc e’s transits and eclipses from 2011 and 2013 and found that they changed quite a lot. Why they’ve changed isn’t clear. Demory et al. speculated that perhaps the planet exhibits extreme volcanic activity, similar to Jupiter’s moon Io, and the erupted material has gone into orbit around the star, causing variable transits and eclipses.

We next discussed the discovery of a new disintegrating rocky planet using data from the K2 mission by Sanchis-Ojeda and colleagues.

This planet, EPIC 201637175 b, zips around its star every 9 hours, and because it’s so hot (1500 K), its rocky surface is evaporating, leaving behind a dust tail, like a comet. Subtle indications of the dust tail appear in the K2 measurements as tell-tale bumps in the light curve, suggesting the dust is scattering light in complicated and surprising ways.

More follow-up work will help us understand this new extreme class of planet, perhaps even allow us to figure out what they’re made of and where they came from.

Attendees at today’s group meeting include Jennifer Briggs, Emily Jensen, Liz Kandziolka, and Tyler Wade.

Artist’s impression of Kepler-22b as an oceanic “super-Earth” within its star’s habitable zone. From http://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets.

At Friday’s journal club, we discussed a recent paper from Montet et al. (2015) that follows up on discovery of planetary candidates observed by the K2 Mission from Foreman-Mackey and colleagues.

Montet and colleagues combined high-spatial resolution and ground-based spectral observations, along with re-analysis of the K2 data, to confirm or refute the planetary status of earlier discoveries. They were able to validate 18 of the original 36 as planets, including a sub-Neptune planet, EPIC 201912552, orbiting a relatively bright M-dwarf star.

As Montet et al. point out, this object is a great candidate for follow-up observations. In fact, it looks like we could see it from Boise State’s Challis Observatory.

Friday’s attendees included Jennifer Briggs, Nathan Grigsby, Catherine Hartman, Tanier Jaramillo, Emily Jensen, and Liz Kandziolka.

We had an abbreviated meeting, as everyone (including myself) seems to have been unusually busy this week. No specific research updates, but we discussed two interesting articles of science news. Attendees were Liz Kandziolka, Jennifer Briggs, Emily Jensen, Brenton Peck, Nathan Grigsby, Trent Garrett, and Prof. Daryl Macomb.

The first article we discussed, “Cosmology from Quantum Potential“, proposed an origin for the universe that represents an alternative to the big bang. We didn’t really understand the theory, but it seems to involve the idea that universe doesn’t really have a beginning. We puzzled over whether the theory actually proposes any specific testables or observables.

The second article we discussed, “Titan Submarine : Vehicle Design and Operations Concept for the Exploration of the Hydrocarbon Seas of Saturn’s Giant Moon“, suggests a plan to send a submersible to plumb the depths of Titan’s seas, the only seas in our solar system besides those on Earth. Studying Titan’s seas may teach us about the pre-biotic chemistry in the Earth’s early oceans. And as with all exciting scientific work, this study comes with an animation and dramatic sound track.

Total amount of water lost for a 1 Earth-mass planet.

In journal club on Friday, we discussed a fascinating paper that presented some problematic results for detecting life on other planets. Luger and Barnes (2014) looked at what could happen to the water on Earth-like planets orbiting many different kinds of stars.

Like the Sun, all stars produce x-rays and ultraviolet light (UV), but not all stars produce the same amount. In fact, stars much less massive than the Sun produce a lot more.

That’s a problem for life on planets orbiting these stars because x-rays and UV (collectively called XUV) can photodissociate (or break-up) water molecules in the atmosphere. Once the water is broken into hydrogen and oxygen atoms, the hydrogen can escape to space so the water is permanently lost, leaving behind the oxygen.

And this isn’t just a hypothetical scenario — Venus probably had oceans, like the Earth, and lost them this way. Of course, water is necessary for life as we know it, so a planet that loses its water can’t host life.

Luger and Barnes modeled this process and found that a lot of planets that might otherwise be suitable for life could actually lose a lot of water. The figure at left shows how much water could be lost for planets in the habitable zones of stars from about 0.1 to 0.9 solar masses (M_⊙). The dark red region shows that most of the planets would actually lose at least 1 oceans-worth of water.

So not only would these planets be bone-dry, they could have a lot of oxygen in their atmospheres. On the Earth, oxygen is produced by photosynthetic planets and algae, and so its presence in a planet’s atmosphere is usually thought of as a smoking gun for life. If Luger and Barnes are right, their results may spell trouble for the search for life elsewhere in the universe.