Rainer Schödel led a study that traced a short-period star around Sagittarius A* at the center of the Milky Way. Ten years of high-resolution astrometry captured both the nearest and farthest parts of the star's highly eccentric orbit.
The 2002 analysis found an orbital period of about 15 years and a close approach of only about 17 light-hours. Concentrating several million solar masses inside that small region excluded plausible extended clusters as the source of the central gravitational field, strengthening the supermassive black hole interpretation.[ref]
Closest Star Seen Orbiting the Supermassive Black Hole at the Centre of the Milky Way by Rainer Schödel and others. Abstract: observed orbital coverage, period, pericentre and excluded extended-mass alternatives
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