Stardust helps date the Milky Way

17 Jun 2002

A new technique uses stellar dust to formulate an age for our galaxy. By looking at the isotopic composition of meteorites, scientists can tell whether certain grains came from outside the solar system. Such specks of matter would also necessarily predate the solar system and would have originated in other stars, either as part of the stellar wind gusting away from red giant stars or as the debris of ancient supernovas.

Larry Nittler, Carnegie Institution of Washington, has sorted 87,000 oxide grains according to two composition ratios: O-16/O-17 and O-16/O-18. From this huge sample he has isolated 87 grains that seem to be "presolar" in nature. Employing these bits of stardust to represent extrasolar material, and using theories about how the heavier elements are cooked in successive cycles of supernovas, Nittler approximates an age for the Milky Way galaxy at14.4 billion years.