Astronomy Picture of the Day |
APOD: 1999 November 21 - Elliptical Galaxy NGC 4881 in Coma
Explanation:
Elliptical galaxies are unlike spiral galaxies
and hence unlike our own Milky Way Galaxy.
The giant elliptical galaxy
named NGC 4881 on the upper left lies at the edge of the giant
Coma Cluster of Galaxies.
Elliptical galaxies are ellipsoidal in shape, contain no
spiral arms,
contain little interstellar gas or
dust,
and are found mostly in rich clusters of galaxies.
Elliptical galaxies appear
typically yellow-red, as opposed to
spirals which have spiral arms that appear quite blue.
Much speculation continues on
how each type of galaxy can form,
on whether ellipticals can evolve from colliding
spirals,
or spirals can be created from colliding ellipticals, or both.
Besides the spiral galaxy on the right, all other images in
this picture are of galaxies that lie well behind the Coma Cluster.
APOD: 2004 June 16 - Elliptical Galaxy M87
Explanation:
Elliptical galaxy
M87 is a type of
galaxy that looks much different than our own
Milky Way Galaxy.
Even for an
elliptical galaxy,
though, M87 is peculiar.
M87 is much bigger than an average galaxy, appears near the
center of a whole
cluster of galaxies known as the
Virgo Cluster,
and shows an unusually high number of globular clusters.
These globular clusters
are visible as faint spots surrounding the bright center of
M87.
In general,
elliptical galaxies contain similar numbers of stars as
spiral galaxies, but are ellipsoidal in shape (spirals are mostly flat), have no spiral structure, and little
gas and
dust.
The
above image of M87 was taken recently by the
Canada-France-Hawaii
Telescope
on top of the dormant volcano
Mauna Kea in
Hawaii,
USA.
APOD: 1999 November 3 - M32: Blue Stars in an Elliptical Galaxy
Explanation:
Elliptical galaxies
are known for their old, red stars. But is this old
elliptical up to new tricks?
In recent years, the centers of
elliptical galaxies
have been found to emit unexpectedly high amounts of blue and
ultraviolet light.
Most blue light from
spiral galaxies originates from
massive young hot stars,
in contrast to the red light from the old cool stars
thought to compose ellipticals.
In the
above recently released, false-color photograph by the
Hubble Space Telescope,
the center of nearby dwarf elliptical M32 has actually been
resolved and does indeed show thousands of bright blue stars.
The
answer is probably that
these blue stars are also old and glow blue, reaching relatively
high temperatures by the
advanced process of
fusing helium, rather than
hydrogen, in their cores.
M32 appears in many pictures
as the companion galaxy to the massive
Andromeda Galaxy (M31).
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
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NASA Official: Jay Norris.
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& Michigan Tech. U.