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Astronomy Picture of the Day |
APOD: 2002 December 29 - NGC 1818: A Young Globular Cluster
Explanation:
Globular clusters once ruled the
Milky Way.
Back in the
old days, back when our Galaxy first
formed, perhaps thousands of globular clusters roamed
our Galaxy.
Today, there are
perhaps 200 left.
Many
globular clusters were destroyed
over the eons by repeated fateful encounters
with each other or the
Galactic center.
Surviving relics are older than any Earth fossil,
older than any
other structures in our Galaxy, and
limit the universe itself in raw age.
There are few, if any, young
globular clusters in our
Milky Way Galaxy because
conditions are not ripe for more to form.
Things are different next door, however, in the neighboring
LMC galaxy.
Pictured above is a "young" globular cluster residing there:
NGC 1818.
Observations show it formed
only about 40 million years ago -
just yesterday compared to the 12 billion year ages of
globular clusters in our own
Milky Way
APOD: 2002 July 30 - A Star Cluster in Motion
Explanation:
Star clusters are a
swarm of complex motions.
The stars that compose
globular clusters and many
open clusters all orbit the cluster center,
occasionally interacting, gravitationally,
with a close-passing star.
The orbits of stars around the cluster are typically
not as circular as the
orbits of planets in our
solar system.
Cluster stars frequently fall more
directly toward the center and many times trace out unusual and
complex loops.
The vast space inside a cluster results in
stars colliding only rarely.
The above computer animation,
derived from a type of computer code called an
N-body simulation, shows 100 identical stars in a
time-lapse movie where hundreds of years pass in one second.
APOD: 2004 October 14 - Glimpse of a Globular Star Cluster
Explanation:
Not a glimpse of
this cluster of stars
can be seen
in the inset visible light image (lower right).
Still,
the infrared view
from the Spitzer
Space Telescope reveals
a massive globular star cluster of about 300,000 suns in
an apparently empty region of sky in the constellation Aquila.
When astronomers used
infrared cameras to peer
through obscuring dust in the plane of our
Milky Way galaxy,
they were rewarded with the surprise discovery of the
star cluster, likely one of the last such
star clusters
to be found.
Globular star clusters normally
roam
the halo of the Milky Way,
ancient relics
of our galaxy's formative years.
Yet the Spitzer image shows this otherwise hidden cluster
crossing through
the middle of the galactic plane some 10,000 light-years away.
At that distance, the picture spans only about 20 light-years.
In the false color infrared image, the red streak is a dust cloud
which seems to lie behind the cluster core.
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:
EUD at
NASA /
GSFC
& Michigan Tech. U.