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NASA Galaxies
Pictures June-October 2009
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The
Tarantula Zone
Credit &
Copyright: John P. Gleason
Explanation: The Tarantula Nebula is more than 1,000 light-years
in diameter -- a giant star forming region within our
neighboring galaxy the Large Magellanic Cloud (LMC). That cosmic
arachnid lies left of center in this sharp, colorful telescopic
image taken through narrow-band filters. It covers a part of the
LMC over 2,000 light-years across. Within the Tarantula (NGC
2070), intense radiation, stellar winds and supernova shocks
from the central young cluster of massive stars, cataloged as
R136, energize the nebular glow and shape the spidery filaments.
Around the Tarantula are other violent star-forming regions with
young star clusters, filaments and bubble-shaped clouds. The
rich field is about as wide as the full Moon on the sky, located
in the southern constellation Dorado.
NGC 6888:
The Crescent Nebula
Credit & Copyright: Daniel López, IAC
Explanation: NGC 6888, also known as the Crescent Nebula, is a
cosmic bubble about 25 light-years across, blown by winds from
its central, bright, massive star. This beautiful portrait of
the nebula is from the Isaac Newton Telescope at Roque de los
Muchachos Observatory in the Canary Islands. It combines a
composite color image with narrow band data that isolates light
from hydrogen and oxygen atoms in the wind-blown nebula. The
oxygen atoms produce the blue-green hue that seems to enshroud
the detailed folds and filaments. NGC 6888's central star is
classified as a Wolf-Rayet star (WR 136). The star is shedding
its outer envelope in a strong stellar wind, ejecting the
equivalent of the Sun's mass every 10,000 years. The nebula's
complex structures are likely the result of this strong wind
interacting with material ejected in an earlier phase. Burning
fuel at a prodigious rate and near the end of its stellar life
this star should ultimately go out with a bang in a spectacular
supernova explosion. Found in the nebula rich constellation
Cygnus, NGC 6888 is about
5,000 light-years away.
The Center
of Globular Cluster Omega Centauri
Credit:
NASA, ESA, and the Hubble SM4 ERO Team
Explanation: What is left over after stars collide? To help
answer this question, astronomers have been studying the center
of the most massive ball of stars in our Milky Way Galaxy. In
the center of globular cluster Omega Centauri, stars are packed
in 10,000 times more densely than near our Sun. Pictured above,
the newly upgraded Hubble Space Telescope has resolved the very
center of Omega Centauri into individual stars. Visible are many
faint yellow-white stars that are smaller than our Sun, several
yellow-orange stars that are Red Giants, and an occasional blue
star. When two stars collide they likely either combine to form
one more massive star, or they stick, forming a new binary star
system. Close binary stars interact, sometimes emitting
ultraviolet or X-ray light when gas falls from one star onto the
surface of a compact companion such as a white dwarf or neutron
star. Two such binaries have now been located in Omega Centauri's
center. The star cluster lies about 15,000 light-years away and
is visible toward the constellation of Centaurus.
The Butterfly Nebula from Upgraded Hubble
Credit: NASA, ESA, and the Hubble SM4 ERO Team
Explanation: The bright clusters and
nebulae of planet Earth's night sky are often named for flowers
or insects, and NGC 6302 is no exception. With an estimated
surface temperature of about 250,000 degrees C, the central star
of this particular planetary nebula is exceptionally hot though
-- shining brightly in ultraviolet light but hidden from direct
view by a dense torus of dust. This dramatically detailed
close-up of the dying star's nebula was recorded by the newly
upgraded Hubble Space Telescope. Cutting across a bright cavity
of ionized gas, the dust torus surrounding the central star is
near the center of this view, almost edge-on to the
line-of-sight. Molecular hydrogen has been detected in the hot
star's dusty cosmic shroud. NGC 6302 lies about 4,000
light-years away in the arachnologically correct constellation
Scorpius.
NGC 7822
in Cepheus
Credit &
Copyright: Don Goldman
Explanation: Pillars of gas, dust, and young, hot stars fill the
center of NGC 7822. At the edge of a giant molecular cloud
toward the northern constellation Cepheus, the glowing star
forming region lies about 3,000 light-years away. Within the
nebula, bright edges and tantalizing shapes are highlighted in
this colorful skyscape. The image includes data from both
broadband and narrowband filters, mapping emission from atomic
oxygen, hydrogen, and sulfur into blue, green, and red hues. The
atomic emission is powered by the energetic radiation from the
hot stars, whose powerful winds and radiation also sculpt and
erode the denser pillar shapes. Stars could still be forming
inside the pillars by gravitational collapse, but as the pillars
are eroded away, any forming stars will ultimately be cutoff
from their reservoir of star stuff. This field spans around 30
light-years at the estimated distance of NGC
Open Cluster M25
Credit & Copyright: Jean-Charles Cuillandre (CFHT) & Giovanni
Anselmi (Coelum Astronomia), Hawaiian Starlight
Explanation: Many stars like our Sun were formed in open
clusters. The above pictured open cluster, M25, contains
thousands of stars and is about two thousand light years
distant. The stars in this cluster all formed together about 90
million years ago. The bright young stars in M25 appear blue.
Open clusters, also called galactic clusters, contain fewer and
younger stars than globular clusters. Also unlike globular
clusters, open clusters are generally confined to the plane of
our Galaxy. M25 is visible with binoculars towards the
constellation of the Archer ( Sagittarius).
Stars,
Dust and Nebula in NGC 6559
Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona
Explanation: When stars form, pandemonium reigns. A textbook
case is the star forming region NGC 6559. Visible above are red
glowing emission nebulas of hydrogen, blue reflection nebulas of
dust, dark absorption nebulas of dust, and the stars that formed
from them. The first massive stars formed from the dense gas
will emit energetic light and winds that erode, fragment, and
sculpt their birthplace. And then they explode. The resulting
morass can be as beautiful as it is complex. After tens of
millions of years, the dust boils away, the gas gets swept away,
and all that is left is a naked open cluster of stars.
SN 1006 Supernova Remnant
Image Credit: NASA, ESA, Zolt Levay (STScI)
Explanation: A new star, likely the brightest supernova in
recorded human history, lit up planet Earth's sky in the year
1006 AD. The expanding debris cloud from the stellar explosion,
found in the southerly constellation of Lupus, still puts on a
cosmic light show across the electromagnetic spectrum. In fact,
this composite view includes X-ray data in blue from the Chandra
Observatory, optical data in yellowish hues, and radio image
data in red. Now known as the SN 1006 supernova remnant, the
debris cloud appears to be about 60 light-years across and is
understood to represent the remains of a white dwarf star. Part
of a binary star system, the compact white dwarf gradually
captured material from its companion star. The buildup in mass
finally triggered a thermonuclear explosion that destroyed the
dwarf star. Because the distance to the supernova remnant is
about 7,000 light-years, that explosion actually happened 7,000
years before the light reached Earth in 1006. Shockwaves in the
remnant accelerate particles to extreme energies and are thought
to be a source of the
mysterious
cosmic rays.
The Trifid Nebula in Stars and Dust
Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona
Explanation: Unspeakable beauty and unimaginable bedlam can be
found together in the Trifid Nebula. Also known as M20, this
photogenic nebula is visible with good binoculars towards the
constellation of Sagittarius. The energetic processes of star
formation create not only the colors but the chaos. The
red-glowing gas results from high-energy starlight striking
interstellar hydrogen gas. The dark dust filaments that lace M20
were created in the atmospheres of cool giant stars and in the
debris from supernovae explosions. Which bright young stars
light up the blue reflection nebula is still being investigated.
The light from M20 we see today left perhaps 3,000 years ago,
although the exact distance remains unknown. Light takes about
50 years to cross M20.
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