Atmospheres of four exoplanets analyzed

After blotting out the host star and some heavy optical and computer processing, the four bodies orbiting HR 8799 become visible.

American Museum of Natural History

In our recent look at exoplanets, we emphasized that it's not enough to simply know where a planet is relative to its host star. To understand the planet's properties, you have to know details about its atmosphere among other things. So researchers have done just that, imaging each of the members of a four-planet system called HR 8799, which is centered on a bright young star about 130 light years from Earth.

Their findings suggest that none of the planets' atmospheres look very much like any of the others, and only one of them looks like a member of our own solar system.

Nearly everything about HR 8799 and its surroundings is rather unusual. (The authors refer to all of it as an exosolar system, in parallel to the term exoplanet.) The star itself has been estimated to be as young as 30 million years old. It's only a bit more massive than the Sun, but quite a bit brighter, especially in the UV. It's also much more variable than the Sun, with large changes in its output occurring over the span of just a few days.