Organic Molecules Seen in an Extrasolar Planet

The Hubble Space Telescope has turned up evidence for organic molecules on a planet orbiting another star. Organic molecules? Like the stuff we’re made of? Yes, but wait, this isn’t the discovery of life. In fact, it’s just the tell-tale signature of methane in the atmosphere of a distant, superheated planet.

The Jupiter-sized extrasolar planet is called HD 189733b, and it orbits a star about 63 light-years away in the constellation Vulpecula. Astronomers discovered that the planet is a member of the “hot Jupiter” class of planets, orbiting so close to its parent star that it only takes 2 days to complete an orbit.

This close orbit, much closer than the orbit of Mercury, raises the planet’s temperature to a sweltering 900 degrees Celsius – about the same temperature as the melting point of silver.

Here’s a computer animated video of the planet.

The observations were made using the transit method. This is where the planet passes directly in front of the parent star from our perspective. As it passes in front, it dims the light from the star slightly. And there’s a special bonus. As the planet is making this transit, astronomers can measure its atmosphere.

Using a technique called spectroscopy, the astronomers were able to split the light coming from the planet to reveal the fingerprints of various chemicals in its atmosphere. They confirmed the existence of water, turned up by NASA’s Spitzer Space Telescope back in 2007. But now they also found methane.

Under the right circumstances, methane can play a key role in prebiotic chemistry – the chemical reactions considered necessary to form life as we know it. Methane has been discovered in other planets in our own Solar System, so it doesn’t mean there’s life on HD 189733b (especially with its extremely hot temperatures). But finding methane around another planet, orbiting another star is an exciting advancement.

So even though life is out of the question on HD 189733b, the technique is the major news here. Astronomers will eventually be peering at smaller, more Earth-sized planets, and will be using this method to find other chemicals of life within stellar habitable zones.

If the life’s out there, astronomers are getting closer and closer to finding it.

The discovery was published in the March 20th issue of the journal Nature.

Original Source: Hubble News Release