free debate

January 14, 2010

Direct Spectrum of an Exoplanet taken for the First Time

Analyzing the spectrum of light coming from a star or planet gives us a huge insight into the composition and environment of that object. If we ever find a exoplanet we think could harbor life, one of the first things we will want to do is get a light spectrum. The would potentially allow us to find free oxygen (a distinct signature of life) in its atmosphere. This makes developing the technique of attaining exoplanet spectrum a huge necessity.

The breakthrough was done on a gas giant orbiting the star HR 8799, which is just slightly larger than our own sun. What makes this measurement special is not that we got a spectrum, but that we got a spectrum straight from the planet itself. In the past we have analyzed the light from a star, that passed through the atmosphere of its exoplanet. While this is still a valid technique, it is only possible to do with planets that have the right orientation to our own solar system. Because only a small fraction of planets have such an orientation, this opens the door to studying the growing number of exoplanets. This planet is extremely hot at about 1,800 degrees Fahrenheit, causing it to pouring out infrared light. This made it a great target for trying this technique, but it was still no walk in the park. “It's like trying to see what a candle is made of, by observing it next to a blinding 300 Watt lamp – from a distance of 2 kilometres [1.3 miles],” said Markus Janson of the University of Toronto, lead author of the paper.

As is almost to be expected with the first results from any new technique, the results from this spectrum were totally unexpected. This planet's spectrum didn't match any of the models we had for gas giants. The current thinking is that this planet was one the verge of becoming a brown dwarf star. With roughly 10 times the mass of Jupiter, it is probably still emitting heat from when it was formed. The composition is also not what was expected from previous models. This once again show how young our models of solar system formation really are.

As we continue to do this on more planets and refine the process, I'm sure we will continue to find things that surprise us. I still think the most exciting part of all this is the ability to use this to find other life in the universe. We will have to wait and see what the future holds, but I think it is promising.

For More Information see the European Southern Observatory site
Image Credit: ESO/M. Janson