Two hundred and nineteen million stars and counting

first_imgA 10-year survey of our home galaxy has yielded an extraordinarily detailed celestial catalog that includes at least 219 million stars. The researchers used a 2.5-meter telescope in the Canary Islands to take more than 7600 images within a 10°-by-185° swath of sky that includes the edge-on view of the Milky Way. In the regions not blocked by interstellar dust (dark areas in the image above, which depicts only a small part of the Milky Way visible from Earth), the researchers could spot individual stars as dim as magnitude 20, about one-millionth as bright as the dimmest star that can be seen with the human eye. Toward the center of the galaxy, the most densely populated part of the team’s star images, the team tallied about 300,000 stars for each square degree of sky. The new catalog contains more than 99 bits of data for each of the 219 million objects surveyed so far, including information about each star’s position, shape, and brightness in various wavelengths, the researchers report online this week in the Monthly Notices of the Royal Astronomical Society. Unfortunately, about 8% of the target area couldn’t be suitably observed during this survey, usually because of bad weather in winter months. Since November 2012, when the decadelong survey ended, researchers have filled in about half of the gaps. Future efforts, they say, will look at the same broad swath of sky in different wavelength bands in order to collect even more data about the stars.last_img