HD 140283

HD 140283 (also known as the Methuselah star) is a metal-poor subgiant star about 200 light years away from the Earth in the constellation Libra, near the boundary with Ophiuchus in the Milky Way galaxy. Its apparent magnitude is 7.205, so it can be seen with binoculars. It is the oldest star currently known. HD 140283's light is somewhat blueshifted as it is moving toward rather than away from the Earth and it has been known to astronomers for over a century as a high-velocity star based on its proper motion. An early spectroscopic analysis by Joseph W. Chamberlain and Lawrence Aller revealed it to have a substantially lower metal content than the Sun. Modern spectroscopic analyses find an iron content about a factor of 250 lower than that of the Sun. It is one of the closest metal-poor (population II) stars to Earth. The star was already known by 1912 when W. S. Adams measured its astrometry using a spectrograph in the Mount Wilson Observatory.