Galactic Dust Bunnies Found to Contain Carbon After All

Written by Raphael Rosen

March 12, 2009

Using NASA’s Spitzer Space Telescope, researchers have found evidence suggesting that stars rich in carbon complex molecules may form at the center of our Milky Way galaxy.

This discovery is significant because it adds to our knowledge of how stars form heavy elements — like oxygen, carbon, and iron — and then blow them out across the universe, making it possible for life to develop.

Astronomers have long been baffled by a strange phenomenon: Why have their telescopes never detected carbon-rich stars at the center of our galaxy even though they have found these stars in other places? Now, by using Spitzer’s powerful infrared detectors, a research team has found the elusive carbon stars in the galactic center.

“The dust surrounding the stars emits very strongly at infrared wavelengths,” says Pedro García-Lario, a research team member who is on the faculty of the European Space Astronomy Center, the European Space Agency’s center for space science. He co-authored a paper on this subject in the February 2009 issue of the journal Astronomy & Astrophysics.

“With the help of Spitzer spectra, we can easily determine whether the material returned by the stars to the interstellar medium is oxygen-rich or carbon-rich.”

The team of scientists analyzed the light emitted from 40 planetary nebulae — blobs of dust and gas surrounding stars — using Spitzer’s infrared spectrograph. They analyzed 26 nebulae toward the center of the Milky Way — a region called the “Galactic Bulge” — and 14 nebulae in other parts of the galaxy. The scientists found a large amount of crystalline silicates and polycyclic aromatic hydrocarbons, two substances that indicate the presence of oxygen and carbon.

This combination is unusual. In the Milky Way, dust that combines both oxygen and carbon is rare and is usually only found surrounding a binary system of stars. The research team, however, found that the presence of the carbon-oxygen dust in the Galactic Bulge seems to be suggestive of a recent change of chemistry experienced by the star.

Full article here:

http://www.spitzer.caltech.edu/Media/happenings/20090312/