Saturday, March 20, 2010

A new hot ball of gas

It hasn't been until recently that astronomers have made great strides in locating planets outside our own solar system -- called exoplanets. The first exoplanets weren't found around normal stars but rather around pulsars (the remnants of dead massive stars). And that was in 1991! Since then astronomers have located hundreds of exoplanets - around 400 actually. A couple of techniques are considered common practice for locating exoplanets.

The Doppler shift technique looks at slight variations in the motions of stars - you can detect a planet tugging on its star or star wobble. A useful, if not very direct, technique. Another technique is to look for planetary transits. In this case the light of the star gets fainter (or is blocked/eclipsed) as the planet crosses in front of it (for more go to transitsearch.org). From these techniques you can get planetary characteristics such as size, mass, and orbit. Additionally, planetary spectroscopy (measuring the wavelengths of light passing through the atmosphere of a planet) can be used to identify various atmospheric attributes. Most of the planets that have been found so far fall within the "hot Jupiter" class. These are enormous gas giants - in many cases, several times the size of Jupiter - that orbit very close to their parent stars - at, or usually closer than, the orbit of Mercury. Needless to say these are very, very hot places.

Now the news: The discovery of another exoplanet has been reported in this week's edition of the journal Nature. This planet can be found in the CoRoT satellite, approximately 1,500 light years from Earth towards the constellation Serpens. The new planet was named Corot-9b (unofficial name Carrot Nimby....give me a second to giggle at that one). This planet regularly passes in front of its star - every 95 days. As with many others, this new exoplanet is a gas giant, it has a radius that is approximately 1.05 times that of Jupiter but is only 84% of its mass. Unlike others, it could have temperatures cool enough to host liquid water, lying between -23°C and 157°C. The planet orbits a sun-like star (similar but slightly cooler) at a distance similar to that of Mercury. It is suggested that the interior of this planet is close to that of Jupiter and Saturn, composed primarily of hydrogen and helium, but which may also contain up to 20 Earth masses of other elements such as water and rock.

Here's a couple of story links:
http://www.nature.com/nature/journal/v464/n7287/full/nature08856.html

http://www.eso.org/public/news/eso1011/

http://www.universetoday.com/2010/03/18/finally-a-normal-exoplanet/#more-60043
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