December 18, 2008

Carbon Dioxide on Extrasolar Planet

Artist's View of the Extrasolar Planet HD 189733b orbiting the star HD 189733

Just a short while ago, the Hubble Space Telescope took the first visible-light photograph of an extrasolar planet, a planet outside our solar system. Now just recently, the space telescope has been used to find the presence of carbon dioxide on an extrasolar planet.

The planet, called HD 189733b, orbiting the star HD 189733, is about the size of Jupiter, and the presence of carbon dioxide on the planet does not prove anything about the presence of extraterrestrial life on there. In fact, the planet is too hot to support life. However, the significance of this discovery was not actually what the telescope found, but the process used to find it.

The process used through the Hubble Space Telescope was used to identify not only carbon dioxide on the planet, but also carbon monoxide, and methane. Just being able to detect, measure, and estimate the amount of something like carbon dioxide on an extrasolar planet is remarkable. This may lay the groundwork for classifying planets by their makeup and potentially looking for signs of life.

This technique (detailed in the picture at right, click for larger view) requires a planet with an orbit tilted towards the Earth edge-on. While orbiting their stars, these planets appear to us to pass in front of their stars, and then go behind the star, a phenomena called an eclipse. When the planet is blocked, only the star's light reaches the Earth. The light emission of the star can be analyzed to tell the chemical composition of the star. This light emission of the star can be analyzed to tell the chemical composition of the star. This light emission is then compared to one taken just before the eclipse, when both the star and the planet's light emissions can be viewed, revealing the chemical compositions of both objects. Since the chemical composition of the star is already known from the star's light emission taken before, this can simply be "subtracted" from the new emission, revealing just the chemical composition of the planet being studied.

Astronomers are also hoping to use similar techniques on NASA's James Webb Space Telescope, after its launch in 2013. This telescope's ability to view near-infrared wavelengths will allow it to better look for biomarkers on a terrestrial planet.

Images: NASA


  1. it was a really informative post..
    did u mean to say that CH4 and CO were found?
    Methane is an organic compound and finding them in an extrasolar place does mean something right? im not telling possibility of life, but it surely is significant.

  2. It definitely is significant, with both CH4 and CO found. Both are organic compounds (since they contain carbon), but are not necessarily formed by life. And we also have to remember that this specific planet is very different from ours. It is huge (the size of Jupiter) and is also very close to its star, and therefore, very hot. These conditions make this planet unlikely for hosting life, at least not the kind that we know.

    The real importance of this is the technique used to find the composition of the planet's atmosphere. This may be used in the future to find planets that can actually support life.