If you think cleanliness is next to godliness, avoid globular clusters. These huge, spherical concentrations of millions of old stars are among the filthiest places in the universe, according to a new study. The stars there pick up ashes from stars that died long ago.
Stellar pollution is exceedingly rare.
It had only been observed in binary star systems where two stars dance around each other at close distances. In the galaxy at large, astronomers say, stars are too far apart to intercept the ashes from old stars before they slowly disperse into space. But in massive globular clusters, stars are much closer together, and their combined gravity is apparently strong enough to keep most of the space pollution in the neighborhood, reports a team led by Raffaele Gratton of the Astronomical Observatory of Padua, Italy. The researchers stumbled across evidence for this kind of stellar pollution in a globular cluster known as NGC 6752, some 13,000 light-years from Earth in the southern constellation Pavo the Peacock. Because the stars in a globular cluster are believed to have formed simultaneously, stars of similar size should have a similar chemical fingerprint.