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07/13/12 1:54 AM
Discover the cosmos!
Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.
2012 July 11
Early morning dog walkers got a visual treat last week
as bright stars and planets appeared to line up.
Pictured above, easily visible from left to right, were the
Pleiades open star cluster,
Venus, and the
Aldebaran, all seen before a starry background.
The image was taken from the
The glow of the rising Sun can be seen over the eastern horizon.
Jupiter and Venus will
continue to dazzle pre-dawn strollers all over planet Earth
for the rest of the month,
even now the
are seen projected away from the line connecting their distant stellar
07/13/12 1:55 AM
Discover the cosmos!
Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.
2012 July 12
Engraved in rock, these ancient
abundant in the Teimareh valley,
located in the Zagros Mountains of central Iran.
a tale of hunters and animals
found in the middle eastern valley 6,000 years ago or more, etched
by artists in a prehistoric age.
In the night sky above are star trails etched by
the rotation of
planet Earth during the long composite exposure made with a modern
On the left, the center of the star trail arcs is the
North Celestial Pole (NCP),
the extension of Earth's axis into space, with
Polaris, the North Star, leaving the bright,
short, stubby trail closest to the NCP.
But when these petroglyphs were carved, Polaris would have
made a long arc through the night.
Since the Earth's rotation axis
like a wobbling top, 6,000 years ago the NCP was near the border of
the constellations Draco and Ursa Major,
some 30 degrees from its current location in
planet Earth's sky.
2012 July 13
One of the last entries in Charles Messier's
famous catalog, big, beautiful spiral galaxy M101 is
one of the least.
About 170,000 light-years across,
this galaxy is enormous, almost
twice the size of our own Milky Way Galaxy.
also one of the original spiral nebulae
observed with Lord Rosse's large 19th century telescope, the
In contrast, this mulitwavelength view
of the large island universe
is a composite of images recorded by space-based telescopes in the
Color coded From X-rays to infrared
wavelengths (high to low energies),
the image data was taken from the
Chandra X-ray Observatory (purple), the
Galaxy Evolution Explorer ( blue),
Hubble Space Telescope(yellow), and the
Spitzer Space Telescope(red).
While the X-ray data trace the location of multimillion degree gas
around M101's exploded stars and neutron star and black hole binary
star systems, the lower energy data follow the
stars and dust that define M101's grand spiral arms.
Also known as the
M101 lies within the boundaries of the northern constellation
Ursa Major, about 25 million light-years
07/23/12 2:56 PM
2012 July 14
Awash in a sea of
plasma and anchored in
fields, sunspots are planet-sized,
dark islands in
solar photosphere, the bright surface of the Sun.
because they are slightly cooler than the surrounding surface,
this group of sunspots is captured in a close-up
telescopic snapshot from July 11.
The field of view spans nearly 100,000 miles.
They lie in the center of active region AR1520, now crossing the
Sun's visible face.
In fact, an
X-class solar flare and
coronal mass ejection erupted
from AR1520 on July 12, releasing some of the energy stored in the
region's twisted magnetic fields.
Headed this way, the coronal mass ejection is expected to
arrive today and may trigger
As a result, some weekend auroral displays could grace
planet Earth's skies along with
predawn conjunction of bright planets and crescent Moon.
2012 July 15
Few cosmic vistas excite the imagination like
the Orion Nebula.
Also known as
the nebula's glowing gas surrounds hot young stars at the edge of an
molecular cloud only 1,500 light-years away.
The Orion Nebula offers one of the best opportunities
to study how stars are born partly because it is the nearest large
but also because the nebula's
energetic stars have
obscuring gas and dust clouds that would otherwise block
our view - providing an intimate look at a
range of ongoing stages
starbirth and evolution.
This detailed image of the
Orion Nebula is the sharpest ever, constructed using data from the
Hubble Space Telescope's
Advanced Camera for Surveys and the European Southern Observatory's
La Silla 2.2 meter telescope.
contains a billion pixels at full resolution
and reveals about 3,000 stars.
07/23/12 2:57 PM
2012 July 16
A fifth moon has been discovered orbiting Pluto.
The moon was
discovered earlier this month in images taken by the
Hubble Space Telescope in preparation for the
New Horizons mission's scheduled
flyby of Pluto in 2015.
Pictured above, the moon is currently seen as only a
small blip that moves around the dwarf planet as the entire system slowly orbits the Sun.
The moon, given a temporary designation of
S/2012 (134340) 1 or just P5 (as labeled), is estimated to span about 15 kilometers and is likely composed mostly of
Pluto remains the only famous Solar System body
never visited by a human-built probe and so its origins and detailed appearance remain
07/23/12 2:58 PM
2012 July 17
How do galaxies like our Milky Way form?
Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out.
Green depicts (mostly) hydrogen gas in the
above movie, while time is shown in billions of years since the Big Bang on the lower right.
is present but not shown.
As the simulation begins, ambient gas falls into and accumulates in regions of relatively high gravity.
Soon numerous proto-galaxies form, spin, and begin to
After about four billion years, a well-defined center materializes that dominates a region about 100,000
across and starts looking like a modern disk
After a few billion more years, however, this early galaxy collides with another, all while
streams of gas from other mergers rain down on this
strange and fascinating cosmic dance.
simulation reaches half the current age of the universe, a single larger disk develops.
Even so, gas blobs -- some representing
small satellite galaxies -- fall into and become absorbed by the rotating galaxy as the present epoch is reached and the movie ends.
Milky Way Galaxy,
however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy
will collide and coalesce with the slightly larger
Andromeda spiral disk galaxy in the next few billion years.
07/23/12 2:59 PM
2012 July 18
What created this unusual hole in Mars?
The hole was discovered by chance on images of the dusty slopes of Mars'
Pavonis Mons volcano taken by the
HiRISE instrument aboard the robotic
Mars Reconnaissance Orbiter
currently circling Mars.
The hole appears to be an opening to an underground cavern, partly illuminated on the image right.
Analysis of this and follow-up images revealed the
opening to be about 35 meters across, while the interior
shadow angle indicates that the underlying cavern is roughly 20 meters deep.
Why there is a circular crater surrounding this hole remains a topic of
as is the full extent of the underlying cavern.
Holes such as
this are of
particular interest because their interior caves are relatively
protected from the harsh surface of Mars, making them relatively good
contain Martian life.
These pits are therefore prime targets for
possible future spacecraft, robots, and even
human interplanetary explorers.
07/25/12 3:15 PM
2012 July 19
Wandering planets Venus and Jupiter were joined by an old crescent Moon
near the eastern horizon on July 15.
serene southern skyview
of the much anticipated predawn
the lovely Pleiades star cluster and bright stars Aldebaran
and Betelgeuse in the celestial lineup.
For help identifying the stars and constellations, just slide your
cursor over the image.
Of course, the radio telescope in the foreground is the
Parkes 64 meter
dish of New South Wales, Australia.
Known for its exploration of the distant Universe
at radio wavelengths,
the large, steerable antenna is also famous for its superior
lunar television reception.
On July 21, 1969 the dish received broadcasts from the Moon
that allowed denizens of planet Earth to
the Apollo 11 moonwalk.
07/25/12 3:16 PM
2012 July 20
around planet Earth enjoyed the close encounter of planets and
Moon in July 15's predawn skies.
And while many saw bright Jupiter next to the slender, waning crescent,
Europeans also had the
opportunity to watch the
ruling gas giant pass
behind the lunar disk, occulted by the Moon as it slid through the
Clouds threaten in this telescopic view from Montecassiano, Italy, but
the frame still captures Jupiter after it emerged from the occultation
along with all four of its large Galilean moons.
The sunlit crescent is overexposed with the Moon's night side faintly
illuminated by Earthshine.
Lined up left to right beyond the dark lunar limb are Callisto,
Ganymede, Jupiter, Io, and Europa.
Callisto, Ganymede, and Io are larger than Earth's Moon, while
Europa is only slightly smaller.
2012 July 21
Get out your
red/blue glasses and
this remarkable stereo view from lunar orbit.
Created from two photographs
taken by astronaut Michael Collins during the 1969
Apollo 11 mission, the 3D
features the lunar module ascent stage, dubbed The Eagle, as it rises to
meet the command module in lunar orbit on July 21.
Aboard the ascent stage are
Neil Armstrong and Buzz Aldrin, the first to
walk on the Moon.
The smooth, dark area on the lunar
surface is Mare Smythii located
just below the equator on the extreme eastern edge of the Moon's
Poised beyond the lunar horizon, is our
fair planet Earth.
07/25/12 3:17 PM
2012 July 22
It was one of the most
of the 1990s.
This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs)
emerging from pillars of molecular
hydrogen gas and
The giant pillars are
light years in length
and are so dense that interior gas contracts gravitationally to form stars.
At each pillars' end,
the intense radiation of bright young stars
causes low density material to boil away, leaving
stellar nurseries of dense
The Eagle Nebula, associated with the
open star cluster
M16, lies about 7000
light years away.
The pillars of creation
imaged again in 2007 by the orbiting
Spitzer Space Telescope in infrared light, leading to the conjecture that
the pillars may already have been destroyed by a local supernova, but light
from that event has yet to reach the Earth.
07/25/12 3:19 PM
2012 July 23
How fast is lightning?
Lightning, in fact, moves not only too fast for humans to see, but so fast that humans can't even tell which direction it is moving.
lightning stroke did not move too fast, however, for
this extremely high time resolution video to resolve.
Tracking at an incredible 7,207 frames per second, actual time can be seen progressing at the video bottom.
The above lightning bolt starts with many simultaneously creating ionized channels branching out from an negatively charged pool of
ions that has somehow been created by
drafts and collisions in a
About 0.015 seconds after appearing -- which takes about 3 seconds in the above time-lapse video --
one of the meandering charge leaders makes contact
with a suddenly appearing positive spike moving up from the ground and
an ionized channel of air is created that instantly acts like a wire.
Immediately afterwards, this hot channel pulses with a tremendous amount
of charges shooting back and forth between the cloud and the ground,
explosion that is later
heard as thunder.
Much remains unknown about
however, including details of the
that separates charges.
07/25/12 3:20 PM
2012 July 24
What's happening over the south pole of Titan?
A vortex of
appears to be forming, although no one is sure why.
above natural-color image
shows the light-colored feature.
The vortex was found on images taken last month when the robotic
flew by the unusual atmosphere-shrouded moon of Saturn.
Cassini was only able to see the
southern vortex because its orbit
around Saturn was recently boosted out of the plane where the rings and moons move.
Clues as to what created the enigmatic feature are accumulating, including that
Titan's air appears to be sinking in the center and rising around the edges.
Winter, however, is slowly descending on the south of Titan, so that
the vortex, if it survives,
will be plunged into darkness over the next few years.
2012 July 25
Why is this aurora strikingly pink?
When photographing picturesque
Crater Lake in
USA last month, the background sky lit up with
auroras of unusual colors.
Although much is known about the
that create auroras, accurately predicting the occurrence and colors of auroras remains a topic of investigation.
Typically, it is known, the lowest
auroras appear green.
occur at about 100 kilometers high and involve atmospheric
oxygen atoms excited by
fast moving plasma from space.
The next highest auroras -- at about 200 kilometers up --
appear red, and are also emitted by resettling atmospheric oxygen.
Some of the highest auroras visible -- as high as 500 kilometers up --
appear blue, and are
caused by sunlight-scattering nitrogen ions.
When looking from the ground
through different layers of distant auroras,
their colors can combine to produce unique and spectacular hues,
in this case rare pink hues seen above.
As Solar Maximum nears over the next two years,
from the Sun are sure to continue and likely to create even more
memorable nighttime displays.
07/26/12 5:12 PM
2012 July 26
Framing a bright emission region
looks out along the plane of our Milky Way Galaxy toward the
nebula rich constellation
Popularly called the Tulip Nebula the glowing cloud of
interstellar gas and dust is also found in the
by astronomer Stewart Sharpless
About 8,000 light-years distant the nebula is
understandably not the only
cosmic cloud to evoke the imagery
The complex and beautiful nebula is shown here in a composite image that
from ionized sulfur, hydrogen, and oxygen atoms
into red, green, and blue colors.
Ultraviolet radiation from young, energetic
O star HDE 227018
ionizes the atoms
and powers the emission from the Tulip Nebula.
HDE 227018 is the bright star very near the blue
arc at image center.
07/27/12 1:42 PM
2012 July 27
The largest of its kind, the
Energy Stereoscopic System (H.E.S.S.) II telescope stands in the
foreground of this photo.
Tilted horizontally it reflects the inverted landscape of
the Namibian desert in a segmented mirror 24 meters wide and
32 meters tall, equal in area to two tennis courts.
Now beginning an
exploration of the Universe at extreme energies,
H.E.S.S. II saw first light on July 26.
Most ground-based telescopes with lenses and mirrors are hindered by
the Earth's nurturing, protective
atmosphere that blurs images and
scatters and absorbs light.
But the H.E.S.S. II telescope is a cherenkov telescope, designed to
detect gamma rays - photons with
over 100 billion times the energy of visible
light - and actually requires the atmosphere to operate.
As the gamma rays impact
the upper atmosphere they produce air
showers of high-energy particles.
A large camera
at the mirror's focus records in detail
the brief flashes of optical light, called
created by the air shower particles.
The H.E.S.S. II telescope operates in concert
with the array of four other 12 meter cherenkov
telescopes to provide multiple stereoscopic views of the air showers,
relating them to the energies and directions of the incoming
cosmic gamma rays.
08/07/12 5:56 PM
2012 July 28
Brilliant Venus and bright Jupiter still rise
together before dawn.
waters by a small
house near Stuttgart, Germany
reflect their graceful arcing trails in this composited series of
exposures, recorded on the morning of July 26.
A reflection of planet
Earth's rotation on its axis, the concentric trails of these celestial
beacons along with
trails of stars
are punctuated at their ends by a separate final frame
in the morning skyview.
Easy to pick out, Venus is brightest and near the trees close to the
Jupiter arcs above it, toward the center of the image along with
the compact Pleiades star cluster and V-shaped Hyades anchored by
bright star Aldebaran.
One trail looks wrong, though.
Not concentric with the others and so not a reflection of Earth's
rotation, the International Space Station streaks off the right
side of this scene, glinting in sunlight
as it orbits planet Earth.
08/07/12 5:57 PM
2012 July 29
In the center of star-forming region
30 Doradus lies a
of the largest, hottest, most massive stars known.
These stars, known collectively as
star cluster R136,
were captured above in
visible light by the
Wide Field Camera
peering through the refurbished
Hubble Space Telescope.
Gas and dust clouds in
30 Doradus, also known as the
have been sculpted into elongated shapes by powerful
from these hot cluster stars.
The 30 Doradus Nebula
lies within a neighboring galaxy known as the
Large Magellanic Cloud and is located a mere 170,000
2012 July 30
Why did the picturesque
2010 volcanic eruption in Iceland create so much ash?
Although the large
ash plume was not unparalleled in its abundance, its location was particularly
noticeable because it
drifted across such well-populated areas.
volcano in southern Iceland began erupting on 2010 March 20,
with a second eruption starting under the center of a small glacier on 2010 April 14.
Neither eruption was unusually powerful.
The second eruption, however, melted a large amount of
glacial ice which then cooled and fragmented lava into gritty
glass particles that were carried up with the
rising volcanic plume.
during the second eruption,
lightning bolts illuminate
ash pouring out of the Eyjafjallajökull volcano.
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