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Carbon Dioxide Detected on Exoplanet HD 189733b

Artist's impression of a transiting exoplanet (ESA - C.Carreau)

Artist's impression of a transiting exoplanet (ESA - C.Carreau)

The Hubble Space Telescope has detected carbon dioxide on a planet orbiting another star. The star in question is HD 189733 (also known as V452 Vulpeculae, a variable star designation), a binary system over 60 light years away, and the planet is approximately the size of Jupiter (called HD 189733b). The exoplanet is already known to contain water and methane molecules from previous Hubble and Spitzer campaigns, but this is the first time CO2 has been discovered.

But why all the fuss? CO2 is another chemical marker for the existance of life. But HD 189733b isn’t a candidate planet for the search for life. After all, this “hot Jupiter” will not be hospitable to the development of even the most basic lifeforms (life as we know it in any case). This discovery is ground-breaking in that CO2 can be sensed on a planet many light years from Earth…

The carbon dioxide is kind of the main focus of the excitement, because that is a molecule that under the right circumstances could have a connection to biological activity as it does on Earth,” said Mark Swain of NASA’s Jet Propulsion Laboratory. “The very fact that we’re able to detect it, and estimate its abundance, is significant for the long-term effort of characterizing planets both to find out what they’re made of and to find out if they could be a possible host for life.”

Indeed, it wasn’t only carbon dioxide that was found; carbon monoxide was also detected in the exoplanet’s atmosphere. But the fact that CO2 is a “tracer” for life and it has been detected on a planet other than a planet known to contain life (Earth) is incredibly significant. As time goes on, observation techniques advance, it is hoped small rocky bodies will be observed. If this can be done, an Earth-like planetary survey can be carried out.

Earth atmospheric molecules detected by Venus Express (ESA)

Earth atmospheric molecules detected by Venus Express (ESA)

In fact, ESA’s Venus Express was recently used to characterize what Earth looks like from a distant vantage point, providing astronomers and future extraterrestrial hunters with a model that can be used when observing distant star systems. If a planet, with a similar chemical composition to that of the Earth is discovered, it would become a prime candidate for harbouring alien life.

So how did Hubble detect CO2 on HD 189733b? Through a spectroscopic analysis of the infrared radiation being emitted by the hot planet, Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) spotted an abundance of CO and CO2. Certain molecules in the exoplanet’s atmosphere absorb certain wavelengths of infrared light, leaving a spectroscopic “fingerprint” in the light detected by Hubble.

This kind of campaign is best carried out on star systems with their ecliptic plane seen edge-on to the Earth. This means the orbit of the exoplanet carries it behind the parent star and then infront of it. HD 189733b transits (or eclipses) its parent star every 2.2 days and then orbits behind the star. This is an ideal situation as astronomers are able to measure the emission from the star (when the line of sight to the exoplanet is blocked by the star) and use those measurements to subtract from spectroscopic analysis of the exoplanet. This technique isolates the exoplanet emission making it possible to analyse the chemical composition of its “day-side” atmosphere.

We’re starting to find the molecules and to figure out how many of them there are to see the changes between the day side and the night side,” Swain said.

All these developments by Hubble will aid the future of exoplanet studies. In 2013, NASA’s James Webb Space Telescope will be launched to look out for “super-Earth” exoplanets (i.e. rocky planets larger than Earth), observing in near-infrared wavelengths. Therefore, the carbon dioxide discovery in the atmosphere of HD 189733b helps astronomers refine techniques to detect yet another tracer for life…

Source: HubbleSite


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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!

Comments on this entry are closed.

  • Astrofiend December 10, 2008, 4:09 PM

    DJ Barney Says:
    December 9th, 2008 at 11:37 pm

    “”We live in times of wonder Simon says” … To Astrofiend … I’m a Trekker and …”

    I’ve got nothing against Trekkers or anything… I enjoy an episode from time to time. I simply used it as a convenient example of the type of spacefaring that is so far beyond anything we’re currently capable of that investigation through science is literally the only way we may come to learn about these far away places. It was simply the counterpoint to Flaming Pope’s view as I understood it.

    Don’t get me wrong though – I think humanity has a fighting chance of one day becoming spacefaring in that sense, but we’d be talking at least hundreds of years even before manned missions beyond the Earth-Moon system become somewhat commonplace.

  • Frank Glover December 10, 2008, 4:31 PM

    “Flaming Pope – we will never, in our lifetime, or the next generations or the two or three after that, be able to harness enough energy to get a manned mission to even the closest stars. The problems involved are simply too great. In fact, I doubt it would be technically possible to have a manned mission travel beyond Mars orbit in our lifetimes without a simply ungodly amount of resources being poured into it, and Mars is over 100,000 times closer than the very nearest star at it’s furthest from the Earth.”

    Don’t be so sure about manned flight beyond Mars. The scientists and engineers of the original Project Orion (the nuclear pulse Orion, not today’s wimpy Apollo-on-steroids) in the late 50’s/early 60’s, expected manned flight to Saturn to be possible as soon as 1970…

    It was not technical or engineering issues that stopped that vision, it was the Test Ban Treaty. Other kinds of nuclear propulsion are possible (and we once did have ground-based nuclear thermal rockets, but after the first Moon landings, support for plans to get to Mars in the 1980’s dried up…and the NERVA program was cancelled, as there was little point in funding an engine without a mission, either), once we become less fearful saying of this other ‘n-word.’ (rational thought seems to stop whenever either one is uttered.)

  • Frank Glover December 10, 2008, 4:32 PM

    “So .. how long till we get a decent hi res piccy of one of these planets ? seeing some blue somewhere else would be even more mind blowing !”

    When we get bigger, badder (and almost certainly space-based) telescopes. Simple as that. We’re operating right on the edge of what’s currently possible, as it is.

  • Bravehart December 10, 2008, 8:04 PM

    I disagree, that our engineering and technology capabilities are ready for space travel! We do have an long way to go in that department. Beside all that, the most important factor is HUMANITY! That alone
    is stopping us from going anywhere! Our life
    span is limited under the current technological posibilities! Untill we are able to travel at light speeds, we have the human factor as a limitation!

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