For the first time ever, astronomers have detected water on an exoplanet that's comparable in size to Earth, and it's also the first time we found a small planet with an atmosphere we could actually get a close look at.
Back in 2014, astronomers from the University of Maryland reported that they found water vapor on a neptune-sized exoplanet called HAT-P-11b.
It sits about a hundred and twenty light-years away in the constellation Cygnus, at about four times the size of Earth. It’s the smallest exoplanet on which we've ever detected water, but that water aside, HAT-P is also probably inhabitable. It orbits its star at a pretty cozy eight million kilometers (close to five million miles) compared to Earth's huge distance from the Sun, so its surface temperature is likely to be extremely hot.
But the fact that it's relatively small combined with the fact that we've been able to detect any kind of molecules there is still significant, because out of the very few small exoplanets that we've found so far all of them have had really thick atmospheres - so thick that the method we use to study them called spectroscopy has been all but impossible.
Spectroscopy analyzes the light from nearby stars as it passes through the planet's atmosphere. Chemicals in the atmosphere absorb different wavelengths of light, so the spectrum of light that we detect can tell us what the atmosphere is made of.
The problem is the outer layers of these smaller worlds have been so highly concentrated that almost no star light can get through. Astronomers don't know why these smaller exoplanets usually have these thick, concentrated cloud layers, but until we found HAT-P-11b, some experts had feared that we just never be able to study the atmospheres of these smaller worlds.
Its discovery proves that there are smaller planets out there with clearer skies and water. Sounds pretty nice, right? Except for the part about the heat melting your face off.
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Sources: This story was originally published on SciShow Space. I am republishing a lightly edited version on SkyFeed in light of interest in the subject. Reimers, Reid. "A 'New Neptune' with Water, and Cyanide in Space." SciShow, YouTube. 2 Oct, 2014. Web video.
Citation: Rovira, Lia N. "We Discovered a 'New Neptune." SkyFeed. 21 May 2018. Web article.