Is there another planet like Earth?
Thursday, May 5, 2011 at 05:25PM Is there another planet like Earth?
As vast as the universe is, it makes sense to think that there are other planets out there that are like the planet Earth. So is there another Earth-like planet?
Any planet that is not found within our own Solar System is called an extrasolar planet, which is often referred to as an exoplanet. Currently, in the spring of 2011, scientists have identified over 540 potential exoplanets beyond our Solar System. One of these exoplanets, discovered in April 2007, is believed to be the most Earth-like of all known exoplanets! This "super-Earth" is called: Gliese 581 C.
Gliese 581 C is one of at least four, and possibly six or more, planets in the Gliese 581 system (located about 20.3 light years away from Earth). It is one of the smallest extrasolar planets discovered to date, but it is still larger than Earth. Said to be about 50% larger than Earth and over five times more massive, Gliese 581 C is the second planet discovered in the Gliese 581 system and sits third in order from its red dwarf star.
(Artist's impression: Gliese 581 system - http://www.space.com/3728-major-discovery-planet-harbor-water-life.html)
Because red dwarfs are a lot smaller, dimmer, and cooler than the Sun, their planets must orbit much closer to them to remain within their "habitable zones". Like Earth, Gliese 581 C is believed to lie within the habitable zone which is located roughly 15 times closer to its star than Earth is to the Sun.
When first discovered, Gliese 581 C was believed to be either a rocky planet like Earth or a waterworld covered entirely by oceans. Initially, it had been estimated that the surface temperatures of this super-Earth lied in the range of 0 to 40 degrees Celsius (32 to 104 degrees Fahrenheit) which would make it possible to maintain liquid water, and thus be suitable for life as known on Earth.
It has since been shown that Gliese 581 c is likely to have a runaway greenhouse effect. This means that it is probably too hot to be habitable, and any potential oceans would be boiled away.
To date, there is still much research being done with the Gliese 581 system to determine which planet, if any, lies within the middle of Gliese 581's habitable zone.