Well, nearby is relative in interstellar space. The new planet, estimated by NASA researchers to be about three times as massive as the earth, orbits a red dwarf star called Gliese 581 every 36 days at a distance of about 13 million miles. The system is about 20 light-years away from earth. That's more than 100 trillion miles! Even the fastest spacecraft ever flown, Voyagers 1 and 2, would take hundreds of thousand of years to reach the planet, designated 581g. We won't be visiting up close anytime soon.
But better and better telescopes are under construction and planned for the near future, both on earth and in space. Starting with NASA's James Webb Space Telescope in 2014, followed by even more advanced arrays, and supplemented by ground based observatories using a new generation of adaptive optics like the Very Large telescope. With these and future devices, it's just a matter of time before astronomers will be able to image planets like Gliese 581g and even get data on chemical composition. That's important, because 581g is about 13 million miles away form its star, which puts it smack dab in the middle of Gliese's Goldilock's zone, not too hot, not too cold, just right for water to exist as a liquid.
Whether there actually is liquid water on 581g is unknown. At three times earth's mass the surface gravity would be about twice what we're used to and plenty powerful enough to hang onto a substantial atmosphere. It could be well be swathed in a thick insulating blanket of gas, something like a cold Venus. And because it orbits between two over-sized super-earths, 581c and 581d, the planet may be heated by tidal flexing and be dotted with volcanoes constantly spewing gas.
So it's a good guess, based on the only terrestrial planets and large moons we have examined up close in our own solar system, that the atmosphere might contain nitrogen and/or carbon dioxide. But 581g could be an ocean planet like a super Europa, or a methane world like a super Titan, or something we have no inkling of because it's totally outside of our experience. Or it could be a rocky world with a mantle of compounds of silica and carbon, a nickel-iron core, and warm surface oceans. And that has astronomers excited.
It would mean Gliese 581g might be habitable, as in a number of species of bacteria from earth could survive and flourish on it. Plus the star is very old, about 7 to 11 billion years old, roughly twice as old as the earth and sun. That means if anything complex has been happening on 581g, it's now had a long, long time to evolve.
One scientist has even gone so far as to speculate the odds of life existing on 581g are "one-hundred percent". That's quite a bold claim, and without more data on the planet's composition and atmosphere, it's quite a stretch to say the least. But red dwarf stars like Gliese 581 are extremely common in our galaxy. There's billions of them, meaning potentially billions of earth-like worlds circling quietly that we currently know nothing about. In fact, NASA's Kepler Mission, only one year into its five-year mission, suggests that smaller, earth-like worlds may be the norm in our galaxy! If so, the odds of life existing on at least one, or a few, or millions, should be pretty good.
Anyway, the image above which was featured on the Astronomy Picture of the Day was produced by my artist friend Karen Wehrstein, and the video below, are about Gliese 581c, but we now think 581c is a little too close, a little too warm. The illustrations could well a better representation of 581g for all we know. We hope to have a new artist's conception of the surface of 581g later today. Speaking of which, we need a better name than 581g, what would you suggest?
Winner of the best name gets a free signed copy of American Taliban.