Are black holes structureless?

Special Colloquium
Prof. Betti Hartmann
Universidade de São Paulo, Brazil

Black holes seem to be fascinatingly structureless - in contrast to other compact, but horizonless objects. Recent gravitational wave observations from the collision of two black holes have demonstrated that these events only produced gravitational and no other radiation. These observational results agree with the theoretical prediction that black holes can be described by a very small number of conserved quantities - mass, charge and angular momentum. However, models appearing in theories that try to explain, e.g., the nature of dark energy or the inflationary epoch in the primordial universe as well as recent studies in applications of the gauge/gravity duality contain black hole solutions that often carry so-called "hair", i.e. non-trivial fields on the event horizon. I will give a review on the current status of the so-called "No hair conjecture" and also mention recent studies and applications of black holes that carry additional structure.

Fifty-two Years of Observations of the Galactic Center in the Infrared

Special Colloquium
Prof. Eric Becklin
SOFIA/USRA and University of California, Los Angeles

In 1964 I started working as a Graduate Student with Gerry Neugebauer and Bob Leighton on the 2.2 micron Sky Survey at Mount Wilson. This led to the first measurements of the infrared radiation from the center of the Milky Way Galaxy in 1966 centered on the radio source Sgr A. I will tell the story of that first discovery and follow up that occurred in the 1970 and 1980's at The Palomar 200 inch telescope, Mount Wilson telescopes, Mauna Kea Hawaii telescopes and especially on the KAO flying 0.9 meter telescope. This included both measurement of stars and dust in the region centered near SgrA* the newly discovered radio point source. The most interesting KAO observation led to the discovery of a ring of dust around Sgr A* (work with Mike Werner and Ian Gatley). In 1995, Andrea Ghez, Mark Morris and I started looking for evidence of a possible massive Black Hole in the Galactic Center. Spectacular observations using the Keck 10 meter telescopes with large format near-infrared arrays and adaptive optics led to the confirmation of the presence of such a black hole and an estimate of its mass (4xE6 M(Sun)). In addition Mark, Andrea and I with the key additions of Leo Meyer, Gunther Witzel and others began multi-wavelength observations of Sgr A*. I will discuss briefly these fabulous results. In 1996, I began working on the Stratospheric Observatory For Infrared Astronomy (SOFIA) and I will finish my talk by discussing SOFIA observations of the ring of dust and gas orbiting the massive black hole in the center of our Galaxy and other recent discoveries.


Main Colloquium
Prof. Laurent Gizon
Max-Planck-Institut für Sonnensystemforschung, Goettingen

How does the solar dynamo work? In order to address this challenging question, we need to understand all the components of motion that maintain the magnetic field in the solar convection zone, using helioseismology. Solar acoustic oscillations have been observed nearly continuously at high spatial resolution for over 20 years by dedicated observatories from space and the ground. The science of helioseismology consists of interpreting the frequencies, amplitudes and phases of the oscillations seen at the surface to make 2D and 3D images of the flows in the solar interior. Important results include, for example, maps of internal rotation (as a function of radius and latitude) and flow patterns associated with convection and magnetic activity. In this presentation I will especially report about the very recent discovery of a new component of solar dynamics at large spatial scales: global equatorial Rossby waves.