NGC 6791: An Old, Large Open Cluster
Explanation:
NGC 6791 is one of the oldest and largest
open clusters of stars known.
But how did it get so dirty?
Open star clusters usually contain a
few hundred stars each less than a billion years old.
Open star cluster
NGC 6791, however, contains thousands of stars
recently measured to be about 8 billion years old.
What's really confusing, though, is that the stars of
NGC 6791 are relatively dirty -
the minuscule amounts of heavy
elements
(generically called metals) are high relative to most other
star clusters.
Older stars are supposed to be metal poor,
since metals have only been slowly accumulating in our
Milky Way Galaxy.
This enigma makes NGC 6791,
pictured above, one of the most studied
open clusters and a possible example of how
stars might evolve in the centers of galaxies.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
