The center of our Galaxy is hidden from view of optical telescopes by thick clouds of obscuring dust in the plane of the Galaxy, but infrared and radio waves from the Galactic Center can penetrate this dust and thus be detected by instruments on Earth. Radio data have revealed the presence of a bright, compact source, called Sagittarius A* (pronounced "A star") that may indicate the presence of black hole. Measurements of the motions of stars and gas near the Galactic Center indicate that the central mass located at Sgr A* has a mass of about one million Suns. Infrared data indicate that the stellar density in the inner light-year is very high, and that some of these stars have unusual properites such as outflows of material at velocities of several hundred km/s. Observations of a tight cluster of a near-infrared sources has been reported very close to Sgr A*, but it is not clear which, if any, of these sources is actually associated with the radio source. Previous attempts to detect a mid-infrared counterpart to this source have been unsuccessful.
We used SpectroCam-10 to image the Galactic center in the summer of 1994. Our goal was to take advantage of SpectroCam's high angular resolution (about 1/2 arcsecond) to obtain the most detailed images of this region ever made.
The first image below is a mosaic of 160 frames, each frame representing a 10 second exposure on the inner 2 light-years of the Galaxy. These were taken in July 1994 using SpectroCam-10 in imaging mode at a wavelength of 8.7 microns. Several previously discovered bright infrared sources, such as the supergiant IRS 7 (bright source at top center with a wind-swept "tail" to the north) are plainly visible, as is extensive emission from diffuse clouds of warm dust. The Sgr A* radio source position lies at the center of the yellow box.
The second image was constructed by deconvolving the first using the image of a bright star that is known to be a point source. This technique approximates the appearance of the imaged field in the absence of diffraction and seeing effects which blur the actual data.
Near the center of the yellow box, close to the Sgr A* position, we detect a faint infrared source against the bright, diffuse background emission. This source appears to be significantly brighter than theoretical models of Sgr A* have predicted. Further measurements will be needed to whether this source is truly coincident with Sgr A*, or is simply a very red, dusty source along nearly the same line of sight.
Further information on this research may be obtained from the on-line version of our paper .