Since 1995, a team of astronomers led by Andrea Ghez has been studying the motion of stars near the center of the Milky Way. They just announced the discovery that one of those stars is the closest to the black hole yet, with an orbital period of about 11.5 years—short enough that they’ve been able to track its entire orbit. This could be good news for testing general relativity in a new regime of strong gravity.

One of the earliest identified S-stars was S0-2, with an orbital period of about 16 years. Until the discovery of S0-102, it was the only star with a sufficiently short orbital period to enable a complete three-dimensional reconstruction of its trajectory, which provided the best data on the shape of the black hole’s gravitational influence. [Read more….]

Animation of star motion near the central black hole, based on real infrared observations. [Credit: Andrea Ghez et al./UCLA/Keck]

The darkness at the center of the galaxy