Astronomy Picture of the Day |
APOD: 2000 October 23 - Dwarf Elliptical Galaxy NGC 205 in the Local Group
Explanation:
Our Milky Way Galaxy is not alone.
It is part of a gathering of about 25 galaxies known as the
Local Group.
Members include the
Great Andromeda Galaxy (M31),
M32,
M33, the
Large Magellanic Cloud, the
Small Magellanic Cloud,
Dwingeloo 1, several small
irregular galaxies,
and many
dwarf elliptical and
dwarf spheroidal galaxies.
Pictured on the lower left is one of the many
dwarf ellipticals:
NGC 205.
Like
M32,
NGC 205 is a companion to the large M31,
and can sometimes be seen to the south of
M31's center in photographs.
The above image shows
NGC 205 to be unusual for an
elliptical galaxy
in that it contains at least two
dust clouds
(at 1 and 4 o'clock - they are visible but hard to spot)
and signs of recent star formation.
This galaxy is sometimes known as M110,
although it was actually not part of
Messier's original
catalog.
APOD: 1999 January 22 - Pegasus dSph: Little Galaxy of the Local Group
Explanation:
The Pegasus dwarf spheroidal galaxy
(Peg dSph) is a
small, newly recognized member of
the Local Group of Galaxies.
Likely a satellite companion of the
Local Group's dominant player, the large spiral
Andromeda (M31),
the Pegasus dwarf galaxy is
almost hidden in the glare
of relatively bright foreground stars
in our own Milkyway.
Still, this
dramatic Keck telescope 3-color image reveals Peg dSph
as a clump of fainter, bluer stars 2,000 or so light-years across.
Excitement over
discoveries of
Peg dSph and other
nearby dwarf galaxies
reflects the fact that
little galaxies may loom large in the
process of galaxy evolution.
They are thought to be the
building blocks from which
larger galaxies are constructed.
APOD: 2004 July 18 - M31: The Andromeda Galaxy
Explanation:
Andromeda is the nearest major
galaxy to our own
Milky Way Galaxy.
Our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including how the center acquired
two nuclei.
APOD: 2001 August 4 - Neighboring Galaxy: The Large Magellanic Cloud
Explanation:
The brightest galaxy visible from our own Milky Way Galaxy is the
Large Magellanic Cloud (LMC).
Visible predominantly from
Earth's Southern Hemisphere, the
LMC is the second
closest galaxy,
neighbor to the
Small Magellanic Cloud,
and one of
eleven known dwarf galaxies that orbit our Milky Way Galaxy.
The
LMC is an
irregular galaxy composed of a bar of older red stars,
clouds of younger blue stars, and a bright red star forming
region visible near the top of the
above image called the
Tarantula Nebula.
The brightest
supernova of modern times,
SN1987A, occurred in the
LMC.
APOD: 2003 November 17 - Canis Major Dwarf: A New Closest Galaxy
Explanation:
What is the closest galaxy to the Milky Way?
The new answer to this old question is the
Canis Major dwarf galaxy.
For many years astronomers thought the
Large Magellan Cloud
(LMC) was closest, but its title was supplanted in 1994 by the
Sagittarius dwarf galaxy.
Recent measurements indicate that the Canis Major dwarf is only 42,000 light years from the
Galactic center,
about three quarters of the distance to the
Sagittarius dwarf
and a quarter of the distance to the LMC.
The discovery was made in data from the
2MASS-sky survey, where infrared light allows a better view through our optically opaque
Galactic plane.
The labeled illustration above shows the location
of the newly discovered Canis Major dwarf and its associated
tidal stream of material in relation to our
Milky Way Galaxy.
The Canis Major dwarf and other
satellite galaxies are slowly being
gravitationally ripped apart as they
travel around and through our Galaxy.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings, and
Disclaimers
NASA Official: Jay Norris.
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EUD at
NASA /
GSFC
& Michigan Tech. U.