Astronomy Picture of the Day |
APOD: 1998 November 7 - Globular Cluster 47 Tucanae
Explanation:
Stars come in bunches.
Of the over 200
globular star
clusters
that orbit the center of our
Milky Way Galaxy,
47 Tucanae is the second brightest
globular cluster
(behind Omega Centauri).
Known to some affectionately as
47 Tuc or NGC 104, it is only visible from the
Southern Hemisphere.
Light takes about 20,000 years to reach us from 47 Tuc
which can be seen near the
SMC in the constellation of
Tucana.
Red Giant
stars
are particularly easy to see
in this
picture.
The dynamics of stars near the center of 47 Tuc are not well understood,
particularly why there are so few
binary systems there.
APOD: 1999 January 17 - 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. But things are different next
door - in the neighboring LMC galaxy.
Pictured above is a "young" globular cluster residing
there: NGC 1818.
Recent 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: 1999 August 19 - M13: The Great Globular Cluster in Hercules
Explanation:
M13
is one of the most prominent and best known
globular clusters.
Visible with binoculars in the constellation of Hercules, M13 is frequently one of the first
steps beyond the ordinary visible to the casual sky gazer.
M13 is a colossal home to over 100,000 stars,
spans over 150 light years across,
lies over 20,000 light years distant,
and is over 12 billion years old.
At the 1974 dedication of
Arecibo Observatory, a
radio message
about Earth was sent in the direction of
M13.
The reason for the low abundance of unusual
blue straggler stars
in M13 is currently unknown.
Authors & editors:
Robert
Nemiroff
(MTU)
& Jerry Bonnell (USRA)
NASA Technical Rep.:
Jay Norris.
Specific rights apply.
A service of:
LHEA at
NASA/
GSFC
&
Michigan Tech. U.