HUBBLE YIELDS DIRECT PROOF OF STELLAR SORTING IN A GLOBULARCLUSTER (STScI-PR06-33)

FOR RELEASE: 10:00am (EDT) October 24, 2006


Ray Villard
Space Telescope Science Institute, Baltimore, Md.
(Phone: 410-338-4514; E-mail: )


Georges Meylan
Ecole Polytechnique Federale de Lausanne (EPFL), Sauverny, Switzerland
(Phone: 011-41-22-379-24-25; E-mail: )


PRESS RELEASE: STScI-PR06-33


HUBBLE YIELDS DIRECT PROOF OF STELLAR SORTING IN A GLOBULAR CLUSTER


NASA's Hubble Space Telescope has provided astronomers with the best
observational evidence to date that globular clusters sort out stars
according to their mass, governed by a gravitational billiard ball
game between stars. Heavier stars slow down and sink to the cluster's
core, while lighter stars pick up speed and move across the cluster to
its periphery. This process, called "mass segregation," has long been
suspected for globular star clusters, but has never before been
directly seen in action.

A typical globular cluster, such as 47 Tucanae, contains several
hundred thousand stars. Although the density of stars is very small in
the outskirts of such stellar systems, the stellar density near the
center can be more than 10,000 times higher than in the local vicinity
of our Sun. If we lived in such a region of space, the night sky would
be ablaze with 10,000 stars that would be closer to us than the
nearest star to the Sun, Alpha Centauri, which is 4.3 light-years away
(or approximately 215,000 times the distance between Earth and the
Sun).

To see and read more about 47 Tucanae on the Web, visit:

http://hubblesite.org/news/2006/33
http://www.spacetelescope.org/news/html/heic0616.html

The Hubble Space Telescope is an international cooperative project
between NASA and the European Space Agency. The Space Telescope
Science Institute is operated for NASA by the Association of
Universities for Research in Astronomy, Inc., Washington.