The proximity of our Galaxy's center (only 8 kpc) presents a unique opportunity to study the environment of a supermassive black hole with much higher spatial resolution than can be brought to bear on any other galaxy. In 1995, we initiated a diffraction-limited study on the W. M. Keck 10-meter telescope, of the Galaxy's central cluster. During this program, we have measured the motions of stars on the plane of the sky and have dramatically improved the case for a supermassive black hole at the Galactic Center, which has evolved through 3 distinct stages of confidence:
- beginning as a possibility, when the earlier, low angular resolution, dynamical measurements of the gas and stars at the center of the Milky Way suggested the presence of 10 million solar masses (10^6) of dark matter and confined it to within a radius of ~0.1 pc
- becoming a strong probability, when proper motion measurements increased the inferred dark mass density by 3 orders of magnitude to 10^12 M_sun/pc^3, thereby eliminating a cluster of dark objects as a possible explanation of the Galaxy's central dark mass concentration, and finally
- crystalizing to a certainty when individual stellar orbits confined the central dark mass to within 0.0004 pc (90 AU), thus increasing the dark mass density by another four orders of magnitude, and eliminating the fermion ball hypothesis as an alternative to a single supermassive black hole.
The unusual radio source SgrA* -- the first known observational manifestation of the black hole -- coincides precisely with the location we infer for the dark mass concentration, as does the X-ray counterpart recently found with Chandra. Many attempts have thus been made to understand the overall spectrum of SgrA* in terms of accretion and/or outflow models, but it has been difficult to apply critical tests of these models in the absence of a detection at near-, mid- or far-infrared wavelengths. This situation has recently evolved quite dramatically. The advent of Adaptive Optics (AO) and a new facility class instrument (NIRC2) at Keck in 2002 led to a number of exciting new results, including the first infrared detection of Sgr A*. This, plus the short-term variability of the emission at several of the observed wavelengths brings us to a promising new era when observations can strongly constrain the wide array of extant models.
As string theory's resident shill, I have to object to your characterisation.
