ASTRONOMERS have pinpointed the black hole at the centre of our galaxy with
unprecedented accuracy by watching three stars wheel around it.
Five years of observations at the Keck Observatory in Hawaii by Andrea Ghez
of the University of California at Los Angeles show the black hole’s gravity
pulling on the stars. This proves that a black hole 2.6 million times the mass
of the Sun must lie within a region just 10 light days across (Nature,
vol 407, p 349). The star nearest the galactic centre may take as little as 15
years to orbit it, according to…
