Lecturer: Dr. Stefan Gillessen
Affiliation: Max Planck Institute
for Extraterrestrial Physics
Abstract:
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, and we have observational hints
that gas passing so close to Sgr A*
experiences a drag force.