Astronomy Picture of the Day |
APOD: 1999 November 14 - 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.
Much about
M31 remains unknown,
including why the center contains two nuclei.
APOD: 1999 June 24 - NGC 1365: A Nearby Barred Spiral Galaxy
Explanation:
Many spiral galaxies have bars across their centers.
Even our own
Milky Way Galaxy is
thought to have a bar, but perhaps not so
prominent as the one in NGC 1365, shown above.
The persistence and motion of the bar imply relatively
massive spiral arms.
The placements of bright young
blue stars and dark dust lanes also
indicate a strong rotating density wave of star formation.
NGC 1365 is a member of the
Fornax
Cluster of Galaxies. Because
NGC 1365 is relatively nearby, simultaneous
measurements of its
speed and distance are possible, which help
astronomers estimate
how fast our universe is expanding.
APOD: 2001 February 3 - M100: A Grand Design
Explanation:
Majestic on a truly cosmic scale,
M100 is appropriately known as a
Grand Design spiral galaxy.
A large galaxy of over 100 billion or so stars with
well defined spiral arms,
it is similar to our own Milky Way.
One of the brightest members of
the Virgo Cluster of galaxies , M100 (alias NGC 4321) is
56 million light-years distant in the spring constellation of
Coma Berenices.
This Hubble Space Telescope image of the central region
of M100 was made in 1993 with the Wide Field and Planetary Camera 2.
It reveals the
bright blue star clusters
and intricate
winding dust lanes
which are hallmarks of this
class of galaxies.
Studies of
stars in M100 have
recently played an important role
in determining the
size and age of the Universe.
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.