Seminar

Seminar Title	The Galactic Center: A unique astrophysical laboratory
Speaker	Dr. Stefan Gillessen
Institute	MPI for Extraterrestrial Physics, Garching
Place	Hannover, AEI, Seminarraum 103
Start	26.01.2017 13:15

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Located at 8kpc only, the Galactic Center allows studying a galactic nucleus in unparalleled detail.
With the advent of high-resolution, near-infrared instrumentation in the last decade it became
possible to follow individual stellar orbits around the radio source Sgr A* with orbital periods
as short as 12 years. The orbits provide compelling evidence for the massive black hole paradigm.
The next generation near-infrared instrument GRAVITY aims at interferometrically combining the light
of the four telescopes of ESO's VLT. The higher resolution will allow monitoring stellar orbits with orbital periods
of 1 year only, and the relativistic prograde periastron precession gets accessible. The astrometric accuracy
of GRAVITY is of order of the event horizon size of Sgr A*. This means that we might have access to
measuring the spin of Sgr A*.
In the past few years the small gas cloud G2 has been approaching Sgr A*. We were able to follow the tidal
evolution of G2 for a decade, beautifully showing how the object got stretched ever more and how it passed
the point of closest approach in 2014. The cloud is a unique probe of Sgr A*'s atmosphere.



The Galactic Center: A unique astrophysical laboratory