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New frontiers of the Milky Way

The Milky Way is an arc of stars and dust, shown in this composition of images captured in Chile

Bruno Gilli/ESO

The disc of the Milky Way, the thin, flat region of the galaxy that is home to our Solar System, may be twice as large as previously estimated, at up to 200,000 light-years in diameter—a light-year is the distance traveled by light in one year, equal to 9.5 trillion kilometers. Astronomers from Spain and China used four methods to estimate the distance to 263,000 stars observed as part of the APOGEE project by the Apache Point telescope in New Mexico, USA, and another 70,000 analyzed by the LAMOST telescope, located in the Hebei province of China. The group found young stars characteristic of the disc up to 100,000 light years from the center of the Milky Way (Astronomy and Astrophysics, May 7). Previous studies have suggested that there is an abrupt drop in the number of these stars at distances beyond 50,000 light-years or less. “The disc of our galaxy is huge,” said astronomer Martin Lopez-Corredoira, lead author of the study, in a press release. The Sun is 25,000 light-years away from the center of the galaxy, and before this study, it was believed to be situated about halfway to the edge. It is now known that the edge of the disc, a bright strip that can be seen at night in areas with no light pollution, is three times as far away.