One of the nearest globular clusters, omega Centauri spans the size of the Full Moon on the sky. Spitzer's fine eye for detail shows many individual red giants even in the densest central parts of the cluster. It also shows many red galaxies at much greater distances, and the astronomers have had to be very careful to eliminate these and stars that do not belong to the cluster, from their analysis.
Stars in omega Centauri have very little of the building blocks for dust grains, and the Spitzer observations have made it crystal clear that dust in such stars only forms when they are at their most luminous. Even then, it seems to require strong pulsating movements of the stellar atmosphere for the material to be pushed out. The Spitzer images show no sign of dust in between the stars of the cluster, suggesting that it leaves the cluster to be mixed with other gas in the Galaxy. Some of the grains formed in this exotic place might one day enter our Solar system!"
Graduate students Martha Boyer (U. Minnesota) and Iain McDonald (U. Keele) did most of the work on the analysis and the publication of these data which feeds their theses. Jacco van Loon (U. Keele) is principal investigator of this programme. The team further includes Robert Gehrz, Charles Woodward (both U. Minnesota), Nye Evans (U. Keele), and Andrea Dupree (Harvard Smithsonian).
The observations were performed with the IRAC and MIPS infrared cameras onboard NASA's Spitzer Space Telescope, and have been published in the Astronomical Journal.