The central region of our Milky Way is an extremely interesting and fascinating field of research. Within few light years we find here ten thousands of stars forming a dense cluster, and the geometric centre of our Galaxy harbours a supermassive black hole with around 3.6 million solar masses. Due to its relative proximity of around 8 kiloparsecs, the Galactic Centre is a perfect laboratory to examine the physical processes in a galactic nucleus.
Our primary goals are to uncover
Time resolved astrometry over a time span of now 17 years allows a description of the proper motions of the Galactic Centre stars. The observations clearly show, that some stars in the immediate vicinity of Sgr A* - i.e. in distances up to around 30 light days - move on Keplerian orbits around the central mass. From the shape of these orbits, the mass of Sgr A* and its distance from the Earth can be calculated.
In order to achieve this, we have observed the central parsec of the galactic center
in near infrared wavelengths since 1992. The main instruments are:
Since the first near-infrared high-resolution observations of the galactic centre in the beginning of the 1990s, the GC was regularly monitored. However, in spite of all efforts, no unambiguous NIR counterpart of SgrA* could be detected up to 2003. On the 9th of May,
during routine observations of the GC star cluster at 1.7 microns with NAOS/CONICA at the VLT, we witnessed a powerful flare at the location of the black hole.
Within a few minutes, the flux of a faint source increased by a factor
of 5-6 and fainted again after about 30 min. The flare was found to
have happened within a few milli-arcseconds of the position of Sgr
A*. The short rise-and-decay times told us that the source of the
flare was located within less than 10 Schwarzschild radii of the black
The Laser Guide Star of the VLT pointing at the Galactic Centre. Image courtesy Yuri Beletsky.
© Infrared and Submillimeter Astronomy Group at MPE
last update: 14/12/2011, editor of this page: Thomas Ott
© Max-Planck-Institut für extraterrestrische Physik