Figure 4:
Measured positions of stars
around the centre of the Milky
Way. The circles show
annually measurements of
the position for a number of
stars, taken using infrared
observations with the W.M.
Keck Telescopes. The
positions are overlaid on an
infrared adaptive optics
image from 2010. The sizes of
the stellar orbits are on the
order of tens of light-days,
and from computing their
Keplerian motions, the mass
of the central object (marked
by a star) can be estimated to
be roughly 4 million times the
mass of the Sun.Credit: This
image was created by Prof.
Andrea Ghez and her
research team at UCLA.