| caption = S2 and Sgr A }} -->

S2 (also known as S0—2) is a star that is located close to the radio source Sagittarius A*, orbiting it with an orbital period of 15.56 ± 0.35 years and a pericenter distance of 17 light hours. Given a recent estimate of 3.7 million M_sun for the mass of Sagittarius A*, the maximum gravitational acceleration experienced by S2 at the pericenter of its orbit would be about 1.5 m/s² or almost one-sixth of Earth's surface gravity.

Its changing apparent position has been monitored since 1995 as part of an effort to gather evidence for the existence of a supermassive black hole in the center of the Milky Way galaxy. The accumulating evidence points to Sagittarius A* as being the black hole. A large part of one orbit had been observed as of 2004.

A team of astronomers mainly from the Max Planck Institute for Extraterrestrial Physics used observations of S2's orbital dynamics around Sgr A* to measure the distance from the Earth to the galactic center. They determined the distance to be 7.94 ± 0.42 kiloparsecs, in close agreement with prior determinations of the distance by other methods.

The 'S' in 'S2' simply stands for 'star'.

External links

• Star Orbiting Massive Milky Way Centre Approaches to within 17 Light-Hours ESO Press Release, October 16 2002
• ESO video clip of orbiting star (533 KB MPEG Video)
• S2 page on the [[SIMBAD] database]
• Photo in ESO press release

Component

References