Older Stars

Stars which are running out of nuclear fuel blast huge amounts of material into space. This material is rich with the heavier elements which have been produced by the star during its burning phases. By studying the infrared spectra of this material which is being ejected into space, we can find out about the elements that a star produces and about the molecules that are formed in the environments around old stars.

Recent spectral data from ISO has shown that complex organic molecules can form rapidly (over a few thousand years) in the environments around old stars. These elements and molecules will likely find their way into new stars and planets as they form from molecular clouds.

To the left is an infrared spectra showing the existence of crystalline silicates - the most common mineral on Earth - around old stars. Compare the spectra of the star to the spectra of a comet in our own solar system. Many of the emission features are the same. The continuum curve is lower for the comet because it has a lower temperature than the star does. Many of the molecules formed around old stars make it into stellar systems - our own solar system contains material created in the environments around stars extinguished before our solar system formed.

Stars eject their material into space in a variety of ways. Most stars will shed their outer atmospheres in layers which we see as planetary nebulae or eject material via high velocity winds. Large stars will explode, creating spectacular supernova remnants. To the right is the infrared spectra of the planetary nebula NGC 6543 taken by the ISO satellite. It clearly shows the fingerprints of sulphur, neon, and argon.