Astronomers scope out alien solar system in detail

Posted by Kate Taylor

Researchers say they've conducted the first reconnaissance of a distant planetary system, collecting the spectra of four red exoplanets which orbit a star 128 light years away from Earth.

Using a suite of high-tech instrumentation and software called Project 1640, the team has been able to create a detailed description of the planets surrounding a star called HR 8799, showing how drastically different they are from the known worlds in the universe. Project 1640 uses the Hale telescope at the Palomar Observatory in California.

"An image is worth a thousand words, but a spectrum is worth a million," says Ben R. Oppenheimer of the American Museum of Natural History.

It's the first time it's been possible to study the planets with spectroscopy, a technique that splits the light from an object into its component colors. Because every chemical, such as carbon dioxide, methane, or water, has a unique light signature in the spectrum, it's a way of revealing the chemical composition of a planet's atmosphere.

In the past, these particular planets have proved impossible to study in this way because of the star's bright light.

The results are 'quite strange', says Oppenheimer: "These warm, red planets are unlike any other known object in our universe. All four planets have different spectra, and all four are peculiar. The theorists have a lot of work to do now."

One abnormality is an apparent chemical imbalance. Basic chemistry predicts that ammonia and methane should naturally coexist in varying quantities unless they are in extremely cold or hot environments. Yet the spectra of the HR 8799 planets, all of which have 'lukewarm' temperatures of about 1340 degrees Fahrenheit, all show just one or the other.

Other chemicals such as acetylene, previously undiscovered on any exoplanet, and carbon dioxide may be present as well.

The planets also are redder than celestial objects with similar temperatures - althouth this could be explained by significant but patchy cloud cover.

"The spectra of these four worlds clearly show that they are far too toxic and hot to sustain life as we know it," says Ian Parry of the Institute of Astronomy, Cambridge University.

"But the really exciting thing is that one day, the techniques we've developed will give us our first secure evidence of the existence of life on a planet outside our solar system."