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Artist's impression of Gliese 581 e. Credit: ESO
After further research on the the star and that planet, it turned out that Gliese 581 c is actually prone to having the runaway greenhouse effect, rendering it unsuitable for inhabitants.
But since a lot of attention was focused on that solar system after Gliese 581 c’s discovery, two more planets were later on spotted there. Gliese 581 d was found in the same year, 2007. Gliese 581 e, on the other hand, was discovered two years later in 2009.
Estimated to have a minimum mass of 1.9 Earth masses (the closest to Earth’s so far), Gliese 581 e is now recognized as the smallest extrasolar planet found near its parent star’s habitable zone.
The planet was discovered by Michel Mayor and his team using the HARPS or High Accuracy Radial velocity Planet Searcher (HARPS) at La Silla Observatory in Chile. Michel Mayor, a professor in the Department of Astronomy at the University of Geneva, wrote a paper entitled “The HARPS search for southern extra-solar planets” with 12 other people.
You can download the pdf of that document by clicking that link.
Not only is Gliese 581 e found outside its parent star’s habitable zone, it is also the innermost among the four planets found orbiting that star, at a distance of only 0.03 AU from Gliese 581 itself. This allows the planet to complete one revolution around the star within a period of only 3.15 days.
Unfortunately, that distance also exposes the planet to very high temperatures. If you were standing on the surface of Gliese 581 e, its parent star would appear no less than 10 times larger than our Sun as it appears on Earth. That would be one very bright day for you, indeed.
If we were to arrange the four planets in the Gliese 581 solar system starting from the outermost one, we would have Gliese 581 d at 0.22 AU, c at 0.07 AU, b, at 0.04, and Gliese 581 e at 0.03. They all have very small eccentricities, with e and b having zero eccentricity. That means, their orbital path is circular unlike the Earth’s which is elliptical.
Universe Today has an article that talks about Gliese 581 and its planets within the habitable zone.
For those who are into Twitter, you might want to check out the article entitled: Send a Tweet to Our Alien Friends on Gliese 581 D.
Of course, there’s more information from NASA. Check out
Habitable World Around Gliese 581? How about an astronomy picture of the day on it instead?
Alternatively, you can also listen to an interesting episode about craters in Astronomy Cast.
Source: ESO
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