Stefan Gillessen talks with
ScienceWatch.com and answers a few questions about
this month's New Hot Paper in the field of Space
Science.
Article Title: Monitoring Stellar Orbits Around The
Massive Black Hole In The Galactic Center
Authors: Gillessen, S;Eisenhauer, F;Trippe,
S;Alexander, T;Genzel, R;Martins, F;Ott, T
Journal: ASTROPHYS J, Volume: 692, Issue: 2, Page: 1075-1109,
Year: FEB 20 2009
* Max Planck Inst Extraterr Phys, D-85748 Garching,
Germany.
* Max Planck Inst Extraterr Phys, D-85748 Garching,
Germany.
* Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. (addresses have been
truncated.)
Why do you think your paper is highly
cited?
This paper summarizes the current status of a large project conducted at
the Max-Planck-Institute for Extraterrestrial Physics (MPE), led by
Reinhard Genzel. Since 1992, the group has been observing the motions of
stars in the very center of the Milky Way, apparently in Keplerian motion
around the central black hole. From such data, a multitude of interesting
conclusions can be drawn.
Particularly interesting is the fact that the mass of the black hole and
the distance to it can be determined in a geometric fashion, i.e., without
any intermediate steps of calibration. Hence, these measurements are very
reliable and therefore, other authors who use either the mass or the
distance in their work frequently cite the MPE paper.
The distance, for example is a key parameter in all models of the Galaxy;
the mass measurement, on the other hand, yields an important point in the
correlation between central black hole mass and galaxy properties such as
the velocity dispersion.
"The future of stellar orbit science in upcoming years
will be dominated by an ever-increasing number of orbits
and an increased accuracy of all quantities involved."
Furthermore, the MPE paper, for the first time, gives the orbital elements
of almost 30 stars. Since these stars are mostly young, the orbital
elements probably can be used as probes for the formation of these stars
orbiting so enigmatically close to the black hole. This currently is a hot
topic in Galactic Center research.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
The paper summarizes and reanalyzes a large data set collected at two
telescopes over 16 years, implementing state-of-the-art, high-angular
resolution techniques of near-infrared observing.
The analysis methods have improved significantly over the past five years,
as a result of which, the black hole in the Galactic Center could be
characterized with unprecedented precision. Also, many new orbits are
presented, bringing the number from one in 2002 and six in 2005 to almost
30 in 2009.
Would you summarize the significance of your paper
in layman's terms?
This paper is important, because it shows that beyond any doubt the center
of the Milky Way hosts a massive, dark object, the mass of which is more
than four million times the mass of the Sun. The most conservative
interpretation of this finding is that there is a black hole.
How did you become involved in this research, and
were there any problems along the way?
Currently I am working as a postdoc in the MPE group. In fact, this project
was the reason why I decided to work at MPE. Hence, stellar orbits are the
main focus of my scientific work. The beauty of this work is that it is
conceptually easy.
This, however, does not mean that it is not cumbersome. Indeed, most of the
work is about fighting systematic error sources and some patience is
required, too, since the stars move fast for astronomical standards, but
timelines of many years are still required.
Where do you see your research leading in the
future?
The future of stellar orbit science in upcoming years will be dominated by
an ever-increasing number of orbits and an increased accuracy of all
quantities involved. A big step forward will happen, once the resolution
can be increased further.
The current generation of telescopes has reached their theoretical limit
and substantial improvements will require either larger
telescopes—such as the
European Extremely Large Telescope—or
interferometers—mainly the
Very Large Telescope Interferometer (VLTI) on Cerro
Paranal in Northern Chile.
Do you foresee any social or political
implications for your research?
There are no social or political implications from this research. Still, it
is worth pointing out that the work done at MPE has some implications for
our view of the Universe: We have to accept that black holes do exist. They
are no longer just theoretical concepts, but reality.
Dr. Stefan Gillessen
MPE IR/Submm Group
Max Planck Institute for Extraterrestrial Physics
Garching, Germany Web |
Web