Somewhere out in the galaxy, orbiting around small, cool stars, there may be a type of planet that we haven't seen before — worlds that bear an uncanny resemblance to eyeballs.
According to astronomers, these 'Eyeball Earths' may be found orbiting around red dwarf stars. These stars are smaller and cooler than our Sun, and as a result, the planets that orbit them would tend to orbit closer in than the planets in our solar system orbit around the Sun.
Planets going around these stars may still be found in the 'habitable zone' — the 'Goldilocks zone' around the star where the temperature and radiation would be 'just right' to make it possible for life to exist. However, since they orbit fairly close to the star, they might become 'tidally-locked'. Like how the Moon is tidally-locked with the Earth, this planet would have one side always facing the star and the other side always facing away. Locked in this position, the surface at the middle of the face pointing at the star would likely be a scorched desert, and the surface facing away from the star would end up entirely frozen, but in between these two regions could be a wide band with liquid water, plants, animals and even intelligent life (if we extend the probabilities far enough).
Thus, the planet would look to us as if it was a giant eyeball floating in space, with an abundance of life in the 'iris'.
"For me, the eyeballs are just one example of the plethora of crazy things we are finding out there in space," said Daniel Angerhausen, an astronomer and astrobiologist at Rensselaer Polytechnic Institute, Troy, N.Y., according to Astrobiology Magazine. "In the field of exoplanets we find hot Jupiters, highly eccentric planets that light up like comets when they come close in to their host star, or evaporating Mercurys — all of them planets that we don't have in our solar system and that astronomers did not even dream about 10 or 20 years ago."
One possible 'Eyeball Earth' is Gliese 581g, apparently. It's considered to be the first habitable zone exoplanet found, but astronomers still need to confirm its existence (not always an easy task). The planet is estimated at being a little over three times the size of Earth, and it orbits a red dwarf with a period of about 36 days, right about in the middle of the star's habitable zone. So, that could put it close enough to its star that it would be tidally-locked while still being in the right place to have liquid water on (at least part of) its surface.
In order to figure out if this is actually possible, and to determine what kind of range there might be to these kinds of worlds, Angerhausen and his group want to start up a research project called Habitability of Eyeball-Exo-Earths, or HABEBEE for short. They plan on modeling different sizes of planets, at different distances from dwarf stars, and then varying the conditions to explore the extremes. This information can then be used when they're searching the stars for these kinds of planets.
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Many astronomers are already looking to explore red dwarf stars for potential 'transiting' planets, because the shorter orbits of these worlds makes it easier to see more transits from them. So, this new project would mesh well with their efforts, and the new James Webb Space Telescope, which is due to be launched in 2018, may even be able to see some of these worlds clearly enough to determine if they really are Eyeball Earths.
(Image courtesy: Beau.TheConsortium)
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