Thursday, September 30, 2010

Found: An Earthlike Planet, at Last

Recently I read news about scientists found an earthlike planet at last. So what is this planet and how does it looks like?

The star known as Gliese 581 is utterly unremarkable in just about every way you can imagine. It's a red dwarf, the most common type of star in the Milky Way, weighing in at about a third of the mass of the sun. At 20 light years or so away, it's relatively nearby, but not close enough to set any records (it's the 117th closest star to Earth, for what that's worth). You can't even see it without a telescope, so while it lies in the direction of Libra, it isn't one of the shining dots you'd connect to form the constellation. It's no wonder that the star's name lacks even a whiff of mystery or romance.

But Gliese 581 does have one distinction — and that's enough to make it the focus of intense scientific attention. At last count, astronomers had identified more than 400 planets orbiting stars beyond the sun, and Gliese 581 was host to no fewer than four of them — the most populous solar system we know of, aside from our own. That alone would make the star intriguing. But on Wednesday, a team of astronomers announced that it had found two more planets circling the star, bringing the total to six. And one of them, assigned the name Gliese 581g, may be of truly historic significance.

For one thing, the planet is only about three or four times as massive as our home world, meaning it probably has a solid surface just like Earth. Much more important, it sits smack in the middle of the so-called habitable zone, orbiting at just the right distance from the star to let water remain liquid rather than freezing solid or boiling away. As far as we know, that's a minimum requirement for the presence of life. For thousands of years, philosophers and scientists have wondered whether other Earths existed out in the cosmos. And since the first, very un-Earthlike extrasolar planet was discovered in 1995, astronomers have been inching closer to answering that question. Now they've evidently succeeded (although to be clear, there's no way at this point to determine whether there is life on the new planet).

I hope sooner or later we will discover whether there is life on that earthlike planet.

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