The accelerations of stars orbiting the Milky Way's central black hole

Abstract

Recent measurements of the velocities of stars near the centre of the Milky Way have provided the strongest evidence for the presence of a supermassive black hole in a galaxy, but the observational uncertainties poorly constrain many of the black hole's properties. Determining the accelerations of stars in their orbits around the centre provides much more precise information about the position and mass of the black hole. Here we report measurements of the accelerations of three stars located approximately 0.005 pc (projected on the sky) from the central radio source Sagittarius A* (Sgr A*); these accelerations are comparable to those experienced by the Earth as it orbits the Sun. These data increase the inferred minimum mass density in the central region of the Galaxy by an order of magnitude relative to previous results, and localize the dark mass to within 0.05 +/- 0.04 arcsec of the nominal position of Sgr A*. In addition, the orbital period of one of the observed stars could be as short as 15 years, allowing us the opportunity in the near future to observe an entire period.

An Improved Distance and Mass Estimate for SGR A* From a Multistar Orbit Analysis

“…The measurement of the high proper motions,and later, accelerations of these stars, implies that they move in the gravitational potential of a concentrated dark mass (Eckart & Genzel 1997;Ghez et al 1998Ghez et al , 2000Eckart et al 2002). With further observations, these stellar motions have provided strong evidence for the presence of a supermassive black hole (SMBH) at the Galactic center (Sgr A * ) with a mass of about 4×10 6 M e .…”

Fluorescent iron lines as a probe of astrophysical black hole systems

“…Modern high-resolution, infrared imaging reveals that the stars in the central-most regions of our Galaxy are orbiting an unseen mass of 2.6 × 10 6 M [ [14][15][16]. Furthermore, studies of the orbital dynamics (which now include measured accelerations as well as velocities; [17,18]) constrain the central mass to be extremely compact. According to conventional physics, the only long-lived object with these properties is a supermassive black hole.…”

Limits on the Short Term Variability of Sagittarius A*in the Near‐Infrared

“…We use proper motion acceleration vectors (Ghez et al 2000) to pinpoint the central black hole's position relative to the nominal radio position of Sgr A* (Menten et al 1997) to within 0. ′′ 04 (1σ).…”

“…The variability of Sagittarius (Sgr) A* at X-ray wavelengths (Baganoff et al 2001a) has bolstered the case for associating this source with the suspected 2.6 x 10 6 M ⊙ black hole at the center of our Galaxy Genzel et al 1997Genzel et al , 2000Ghez et al 1998Ghez et al , 2000. In two Chandra observations separated by almost a year and having a total of 76 ksec of exposure time, Sgr A* was detected at X-ray wavelengths for the first time and was also seen to flare in intensity over a time scale of 3 hours (Baganoff et al 2001a,b).…”

“…The W. M. Keck Observatory dynamical study of stars in the central stellar cluster (Ghez et al 1998(Ghez et al , 2000Gezari et al 2002) provides a rich source of high angular resolution 2µm data between 1995 and 2001. In this paper, we present 2µm flux density limits from maps that were each composed of data from a single night.…”