Video clip: Orbit of the S2 star near the Galactic centre

This video clip shows the observed motions of S2 and other stars in an area around the central black hole of the Milky Way. These unique data show unambiguously that S2 is moving along an elliptical orbit with SgrA* at one focus, i.e., S2 orbits SgrA* like the Earth orbits the Sun.

The superb data also allow a precise determination of the orbital parameters (shape, size, etc.). It turns out that S2 reached its closest distance to SgrA* in the spring of 2002, at which moment it was only 17 light-hours away from the radio source, or just 3 times the Sun-Pluto distance. It was then moving at more than 5000 km/s, or nearly two hundred times the speed of the Earth in its orbit around the Sun. The orbital period is 15.2 years. The orbit is rather elongated - the eccentricity is 0.87 - indicating that S2 is about 10 light-days away from the central mass at the most distant orbital point.

Model calculations now indicate that the best estimate of the mass of the Black Hole at the centre of the Milky Way is 2.6 ± 0.2 million times the mass of the Sun.



Credit: The Max-Planck Society and the European Southern Observatory (ESO)

http://www.eso.org/outreach/press-rel/pr-2002/pr-17-02.html

The original video can be found here.