MIT can detect alien weather, including clouds laced with liquid rock

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For a long time, simply proving the existence of exoplanets was a big deal. We had over a hundred years of fiction and even non-fiction based on the assumption that our universe is absolutely packed with alien planets — but we simply couldn’t prove that they existed. Now, with the list of planets outside our solar system ballooning by dozens or more at a time, the stakes are quite a bit higher. Simply finding and identifying exoplanets is no longer enough to impress, and now you have to actually learn something about them. That’s been the goal of a team from MIT, which this week publishes a piece detailing their pioneering new method for looking at alien weather.

That’s much easier said than done, however, for many of the same reasons that it took so long to confirm the existence of exoplanets in the first place: they are very small and very dark. Most exoplanets have been confirmed thanks to so-called “transit” in front of their parent star, producing a blown-own planetary silhouette. Astronomers have worked to pull much more useful data from these transits than simple size and speed, and this MIT paper represents a major step toward that goal. By looking at the fluctuations in any light spilling around the edges of an alien world, these researchers can gain some insight into its atmosphere. Particularly, the team can derive some real information about the clouds that sit on top of this atmosphere.

The technique starts with a climate model that uses predicted pressure values to predict how different substances will behave on the surface of a given planet. This gives the team a mixture of gaseous products to model, and the software then looks at how these gasses might interact on the surface of an alien world with particular properties. The software spits out a prediction for the spectrographic readings we’d expect to be associated with each of these possible cloud formations. After that, all they need to do is compare their actual readings to the list of predictions — if any of the values fits observation too well to be coincidence, that’s probably our culprit.

The team used Kepler 7b as a test bed for its technique, and their readings suggest that the planet has clouds made of vaporized rock. On Earth these substances would be solid, or at most liquid near the planet’s interior. However Kepler 7b is absolutely gargantuan (one reason it was one of the first five confirmed exoplanets) and orbits less than a twentieth of as far from its star as the Earth does from Sol; sometimes referred to as a “hot Jupiter,” Kepler is a nightmarish furnace to make Venus look hospitable.

NASA’s TESS mission could make even these findings look tame.

These incredible rock-clouds are just another bullet point on the list of reasons exoplanetologists have the coolest scientific conferences. Their results often read like the ramblings of a science fiction author, narrating a magellan-like voyage through a universe far too surreal to ever actually exist. Worlds have been shown to rain diamond, or simply to be composed almost entirely of it. Others have multiple sunsets or abnormally long or short years. Astronomers have found planets that are several times older than our Sun, and others that are younger than our upright ancestors. The search for alien planets is the search for the edges of what’s possible, and techniques like this one are proving that we are very far from finding them.

While Kepler was mankind’s first tailored planet hunter, NASA is already well underway on its successor: the Transiting Exoplanet Survey Satellite, or TESS. TESS should take our understanding of exoplanets to a new level, and unlike many areas of astronomy, in this case the tinier the detail of the observation the more relatable it is to the average person. It’s hard to imagine a super-Jupiter, but easier to imagine clouds. Exoplanetology will almost certainly be one of the most publicly lauded areas of astronomy in years to come.