Found: An Earthlike Planet, at Last

Found: An Earthlike Planet, at Last

Gliese 581g is smack in the middle of the habitable zone

By Michael D. Lemonick for TIME

The star known as Gliese 581 is utterly unremarkable in almost every way you can imagine. It's a red dwarf, the most common type of star in our galaxy, the Milky Way. At 20 light years away, it is relatively nearby. (A light-year is nearly 6 trillion miles. And, a trillion is a million million!) But there are 116 stars that are closer than Gliese 581. You can't even see Gliese 581 without a telescope. It's no wonder that the star's name lacks even a whiff of mystery. But Gliese 581 does have one distinction. On September 29, a team of astronomers announced that they had found two more planets circling the star, bringing the total to six. And one of the planets, which was given the name Gliese 581g, may be of truly historic significance. Gliese 581g is in the "Goldilocks" zone. It is far enough away from its home star that temperatures are not too hot, but close enough that they're not too cold either, and thus just right for the possibility of life. Gliese 581g is a lot like Earth.

Do Other Earths Exist?

Gliese 581g probably has a solid surface just like Earth. Much more important, it sits smack in the middle of the Goldilocks zone. It orbits 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, scientists have wondered whether other Earths existed out in the universe. And since the first, very un-Earthlike planet outside our solar system was discovered in 1995, astronomers have been inching closer to answering that question. Now they have evidently succeeded. But to be clear, there's no way at this point to determine whether there is life on the new planet.

"We're pretty excited about it," admits Steve Vogt of the University of California at Santa Cruz, a member of the team that found the planet. "This is right next door to us. That's the big result."

A Remarkable Achievement

Lost in the excitement over possible life on the new world is what a remarkable achievement its mere discovery was. Detecting a planet this small is monstrously hard. It takes sensitive instruments and careful observation. It would have been impossible to detect a planet this small when Vogt and co-discoverer Paul Butler of the Carnegie Institution of Washington first got into the planet-hunting game in the early 1990s. The instruments simply were not sensitive enough. Since then, says Vogt, he has been working hard "to improve the instruments." And, he says, Butler has been working just as hard to do the observations.

There is no proof that there is water on Gliese 581g. "Those are things we just have to speculate about," says Vogt. But he goes on to point out that there's water pretty much everywhere else you look. "There's water on Earth," he says, "and on the moon, and Mars, and on Jupiter's moon Europa and Saturn's moon Enceladus, and in interstellar space."

It's not hard to imagine, in other words, that Gliese 581g might have plenty of water as well. "It could have quite a good ocean," Vogt says. Maybe there's no life in that ocean. But unlike any planet found until now, there's nothing to rule out the idea that it could be full of life.

Max- I think finding another Earth is good for us. The planet must have the same things than Earth. Like these six planets, the have the same kind of things, like they have water, but not letting it freeze or evaporate, and it is solid, not other gas planets like Saturn and Uranus, and the temperature in that planet is not too cold or not too hot. Many people would think this is good, because one day they would demolish the Earth, and go to other planets so that they would live. But I think we must protect the Earth, and demolish the Earth even when new Earth-like planets are found. This planet hunting game started 20 years ago, and I think the planets they found first are just totally different from Earth. Some years later, scientist found some planets that were partly similar from Earth, but we can’t live on those planets, either. Some scientists prefer we can stay on Mars, because it is the same weather, but a day in Mars is just a bit longer than Earth. Now we found this kind of planet that we could stay, maybe we can find a planet very similar from Earth in the next few years.