Wednesday, September 4, 2013
Hints of Water on a Super-Earth
A Japanese team of astronomers, using the giant Subaru telescope, atop an extinct volcano in Hawaii, have found further hints of the presence of water on a planet orbiting the star Gliese 1214, about 40 lightyears away.
The planet orbits its star in only 38 HOURS (not days, folks, but hours!) You might think that a planet this close to a star will soon be french fried, but, in this case, the star itself is much dimmer and cooler than the Sun -- it is what astronomers call a "red dwarf."
The planet circling the red dwarf is one of the few planets outside our own solar system which we have been able to find in two independent ways. We know it's there because its gravity makes the star wiggle a bit, and we also know it's there because we can see the planet move across the face of the star and cause a mini-eclipse (or transit).
This double identification is very helpful, since it lets us measure both the size of the planet and how much stuff (mass) it contains. That's how we know it's a "super-Earth" -- a kind of planet we don't have in the Sun's family. This super-Earth is about three times the size of Earth, and more than 6 times its mass. These characteristics make this alien world denser than Jupiter but less dense than Earth. It could be a little rocky planet with a giant atmosphere, or a planet with some rock and a lot of liquid water surrounding it.
The new Japanese study examined the planet's atmosphere and concluded that the way light of different colors scattered from it was consistent with either the presence of water vapor or with some kind of extensive cloud cover. Combining this work with other studies makes astronomers a bit more sure that this is a water-rich environment. That still doesn't help us pin down exactly what this super-Earth looks like, and it's probably too warm overall for life as we know it. Nevertheless, isn't it amazing that we can now discover not only planets out there in other parts of the Galaxy, but even something about the kind of air they have surrounding them?
(NOTE: The image above is an artist's conception of what the star might look like through a blue filter. The star itself would look red to your eye. The planet is the smaller black sphere on the left side of the star.)