December 20, 2009

A Nearby Watery Planet

A new rocky planet, GJ 1214b, has been found very close to the solar system, one of a few hundred exoplanets currently known. Making this discovery special, though, is that the planet contains water, being almost completely covered by it, and that its mass is just a little bit greater than the Earth's.

However, it is probably not a planet life could exist easily on. The temperature on the surface is estimated to be about 200 degrees Celsius (400 degrees Fahrenheit). And it is not yet confirmed whether or not water exists on the planet as a gas or liquid, or maybe even some other state (the large pressure from the atmosphere may be causing the water to be in a liquid state despite the high temperature). Yet, this and other findings about the planet place it to be very close to the habitable zone. It is 2.7 times the size of the EArth and the mass of the planet is 6.6 times greater than that of the Earth. If only a few of these conditions were slightly changed, than the planet would be a great candidate for life. These also put the planet in the rapidly growing exoplanet category of "Super-Earth," the members of which have masses between those of Earth and Neptune.

The discovery was made by astronomers using a bank of telescopes (named MEarth) in Arizona, with each telescope having a 16 inch diameter (about the same size that many amateur astronomers possess). They analyzed 2000 nearby cool and dim stars, like GJ 1214, the star of the new planet found. There is a great number of these stars, and their dim light levels easily allows finding planets orbiting around them.

Astronomers were able to calculate size and density of the planet using a rare characteristic of the planet: its orbit falls in line with its star as seen from Earth. When the planet crosses in front of its star, the drop in the light reaching Earth allows calculation of the diameter of the planet. Additionally, reading the small movements in the position of the star from the gravitational pull of the planet allowed calculating the planet's mass. These two characteristics led to finding the density of the planet.

Probably the most important consequence of the discovery is the suggestion that there is a great number of Super-Earths around us, and many may have the potential to harbor life. It also suggests that many of these planets may be in closer proximity to the Earth, allowing for better analysis. In fact this new planet found is so close to the Earth, our communication signals (like radio and TV) have already reached it.

Astronomy and Space Celebrates International Year of Astronomy 2009.

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