APOD
The Astronomy Picture of the Day is a wonderful web site that puts up a different astronomy-related picture every day. However, the site does not have an RSS feed. This page fixes that deficiency.
Updated: 2 hours 11 min ago
Yukon Aurora with Star Trails
Yukon Aurora with Star Trails
Fixed to a tripod, a camera can record graceful trails
traced by stars
as planet Earth
rotates on its axis.
But at high latitudes during
March and April,
it can also capture an
aurora shimmering in the night.
In fact, the weeks surrounding the equinox, in both spring and fall,
offer a favorable
season for aurora hunters.
The possibilities are demonstrated in this beautiful moonlit vista
from northwestern Canadian territory the Yukon.
It was taken during the early morning of March 1, off
the Klondike Highway
about 60 kilometers south of Dawson City.
To compose the picture, many short exposures were digitally
combined to follow the concentric star trail arcs while including
the greenish auroral curtains also known as
the
northern lights.
Saturn's Moon Helene from Cassini
Saturn's Moon Helene from Cassini
What's happening on the surface of Saturn's moon Helene?
The moon was imaged in
unprecedented detail last week as the
robotic
Cassini spacecraft orbiting Saturn
swooped to within
two Earth diameters of the diminutive moon.
Although conventional craters and hills appear, the above raw and unprocessed image also
shows terrain that appears unusually smooth and
streaked.
Planetary astronomers will be inspecting these detailed images of
Helene to glean clues about the origin and evolution of the 30-km across floating iceberg.
Helene is also unusual because it circles Saturn just ahead of the large moon
Dione, making it one of only four known moons to occupy a gravitational well known as a stable
Lagrange point.
Galaxies Beyond the Heart: Maffei 1 and 2
Galaxies Beyond the Heart: Maffei 1 and 2
The two galaxies on the far left were unknown until 1968.
Although they would have appeared as two of the brighter galaxies on the night sky, the opaque dust of the
central band of our
Milky Way Galaxy had
obscured them from being seen in visible light.
The above image in
infrared light taken by the recently launched
Wide-Field
Infrared Survey Explorer
(WISE),
however, finds these galaxies in
great detail
far behind -- but seemingly next to -- the
photogenic Heart nebula (IC 1805).
The spiral galaxy
near the top is the easiest to spot and is known as
Maffei 2.
Just below and to its right is fuzzy-looking
Maffei 1,
the closest giant
elliptical galaxy to Earth.
The above
false-colored image spans three
full moons from top to bottom.
The Maffei galaxies each span about 15,000 light years across and lie about 10 million
light years away toward the
constellation of the Queen of
Ethiopia (Cassiopeia).
On the image right, stars, gaseous filaments, and warm
dust highlight a detailed
infrared view
of the Heart nebula.
Mars Over the Allalinhorn
Mars Over the Allalinhorn
What's that bright object in the sky?
A common question with
answers that vary by time and season, the quick answer
just after sunset in middle of last month, from the norther hemisphere, was Mars.
The above picturesque panorama, taken during a ski trip from the
Alps in
Switzerland,
shows not only
Mars, but much more.
Pine trees line the foreground,
while numerous slopes leading up to the snow covered
Allalinhorn mountain are
visible in the distance.
Stars dot the background, with the
Beehive star cluster (M44) visible just below and to the left of Mars, while stars
Castor and
Pollux
peak through the tree tops to the Mars' upper right.
Mars will remain bright and in the
constellation of the Crab (Cancer) until mid-May.
Spirit Rover at Engineering Flats on Mars
Spirit Rover at Engineering Flats on Mars
Is it art?
If so, the paintbrush was the
Spirit robotic rover,
the canvas was the
soil on Mars,
and the artists were the
scientists and engineers
of the Mars Exploration Rover Mission.
This panoramic picture, created in 2004 and shown above compressed horizontally, was mostly unintentional -- the
MERS
team was primarily instructing Spirit to investigate rocks in and around
Hank's Hollow in a location called
Engineering Flats on Mars.
After creating the ground display with its treads, the
Spirit rover was instructed to
photograph the area along with itself in
shadow.
In 2010 as winter approaches in northern Mars, Spirit, still
mired in sand,
has been
placed in an energy saving "hibernating" mode until
spring arrives and more direct sunlight might be used to
power the robotic explorer.
Pillar at Sunset
Pillar at Sunset
Reddened
light from the setting Sun illuminates the cloud banks
hugging this snowy, rugged terrain.
Inspiring a moment of quiet contemplation,
the sunset scene
included a remarkable pillar of light that seemed to
connect the clouds in the sky with the mountains below.
Known as a
Sun pillar,
the luminous column was produced by
sunlight reflecting from flat,
six-sided ice crystals formed high
in the cold atmosphere and fluttering toward the ground.
Last Monday, astronomers watched
this Sun pillar slowly fade, as the
twilight deepened and clearing, dark skies
came to Mt. Jelm and the
Wyoming Infrared Observatory.
Deep Auriga
Deep Auriga
The plane of our Milky Way Galaxy runs right
through
Auriga, the Charioteer.
A good part of the ancient northern constellation's
rich collection of nebulae and star clusters is featured in
this expansive, 10 degree wide skyscape.
Bright star
Elnath
lies near the bottom right,
linking Auriga to another constellation, Taurus, the Bull.
Three open star clusters, Charles Messier's
M36,
M37, and
M38 line up in the
dense star field above and left of Elnath, familiar to many
binocular-equiped skygazers.
But the deep exposure also brings out the reddish emission nebulae
of star-forming regions
IC 405,
IC 410, and
IC 417.
E. E. Barnard's dark nebulae B34 and B226
just stand out against a brighter background.
For help identifying even more of Auriga's deep sky highlights,
put your cursor over the image.
NGC 4565: Galaxy on Edge
NGC 4565: Galaxy on Edge
Magnificent spiral galaxy
NGC 4565
is viewed edge-on from planet Earth.
Also known as the Needle Galaxy
for its narrow profile, bright NGC 4565 is a stop
on many telescopic tours of the northern sky,
in the faint but well-groomed
constellation Coma
Berenices.
This
sharp, colorful image reveals the galaxy's bulging central core
cut by obscuring dust lanes that lace
NGC 4565's thin galactic plane.
An assortment of other galaxies are included in
the pretty field of view.
Neighboring galaxy NGC 4562
is at the upper right.
NGC 4565 itself lies about 40 million
light-years distant, spanning
some 100,000 light-years.
Easily spotted with small telescopes,
sky
enthusiasts consider
NGC 4565 to be a prominent celestial masterpiece
Messier missed.
The International Space Station from Above
The International Space Station from Above
The International Space Station (ISS) is the largest human-made object
ever to orbit the Earth.
The ISS is so large that it can be seen drifting overhead with the unaided eye, and is
frequently
imaged
from
the
ground
in
picturesque
fashion.
Last month, the station was
visited again by
space shuttle,
which resupplied the station and added a
new module.
The ISS is currently operated by the Expedition 22 crew, now consisting five astronauts including two supplied by
USA's NASA, two by
Russia's RKA,
and one by
Japan's JAXA.
After departing the
ISS, the crew of the space shuttle Endeavour captured
the above spectacular vista of the orbiting
space city high above the clouds, waters, and lands of Earth.
Visible components include modules,
trusses, and expansive
solar arrays
that gather sunlight that is turned into needed
electricity.
M78 and Reflecting Dust Clouds in Orion
M78 and Reflecting Dust Clouds in Orion
An eerie blue glow and ominous columns of
dark dust highlight M78 and other bright
reflection nebula
in the constellation of Orion.
The dark filamentary
dust not only absorbs light, but also reflects the
light of several bright blue stars that
formed recently in the nebula.
Of the two reflection nebulas
pictured above, the more famous nebula is
M78, in the image center, while
NGC 2071 can be seen to its lower left.
The same type of scattering that colors the
daytime sky further enhances the blue color.
M78
is about five
light-years across and visible through a small telescope.
M78 appears above only as it was
1600 years ago,
however, because that is how long it takes light to go from
there to here.
M78
belongs to the larger
Orion
Molecular
Cloud
Complex
that contains the
Great Nebula in Orion and the
Horsehead Nebula.
Slope Streaks in Acheron Fossae on Mars
Slope Streaks in Acheron Fossae on Mars
What creates these picturesque dark streaks on Mars?
No one knows for sure.
A leading hypothesis is that streaks like these are caused by
fine grained
sand sliding down the banks of troughs and craters.
Pictured above,
dark sand appears to have flowed hundreds of meters down the slopes of
Acheron Fossae.
The sand appears to
flow
like a liquid around boulders, and, for some reason,
lightens significantly over time.
This sand flow process is one of several which can rapidly change the surface of Mars, with other processes including
dust devils,
dust storms, and the freezing and
melting of areas of ice.
The above image
was taken by the
HiRise camera on board the
Mars Reconnaissance Orbiter which has been orbiting Mars since 2006.
Acheron Fossae
is a 700 kilometer long
trough in the
Diacria quadrangle
of Mars.
Pauli Exclusion Principle: Why You Don't Implode
Pauli Exclusion Principle: Why You Don't Implode
Why doesn't
matter just bunch up?
The same principle that keeps
neutron stars and
white dwarf stars
from imploding also
keeps people from imploding and makes
normal matter mostly empty space.
The observed reason is known as the
Pauli Exclusion Principle.
The principle states that identical
fermions -- one type of
fundamental matter -- cannot be in the same place
at the same time and with the same orientation.
The other type of matter, bosons, do not have this property, as
demonstrated clearly by recently created
Bose-Einstein condensates.
Earlier this decade, the
Pauli
Exclusion Principle was
demonstrated graphically in the
above picture of clouds of two
isotopes of lithium -- the left cloud composed of
bosons while the right cloud is composed of
fermions.
As temperature
drops, the bosons bunch together, while the
fermions better keep their distance.
The reason why the
Pauli Exclusion Principle is true and the physical limits
of the principle are still unknown.
Dawn's Endeavour
Dawn's Endeavour
On February 21st, the Space Shuttle Endeavour and the International
Space Station (ISS) flew through the sky near
dawn over Whitby, Ontario, Canada.
Along with star trails, both were captured in this single time exposure.
Glinting in sunlight 350 kilometers above the Earth,
Endeavour slightly
preceeded the ISS arcing over
the horizon.
But the brighter trail and the brighter flare
belongs to the space station just visted
by Endeavour.
Near the completion of the STS-130 mission,
hours later Endeavour made a
night landing
at Kennedy Space Center.
Chasing Carina
Chasing Carina
A jewel of the southern sky,
the Great Carina Nebula, aka NGC 3372,
spans over 300 light-years.
Near the upper right of
this
expansive skycape, it is
much larger than the more northerly
Orion Nebula.
In fact, the Carina Nebula is one of our
galaxy's largest star-forming
regions and home to young, extremely massive stars,
including the still
enigmatic variable Eta Carinae,
a star with well over 100 times the mass
of the Sun.
Nebulae near the center of the 10 degree wide field include
NGC 3576 and
NGC 3603.
Near center at the top of the frame is open star cluster
NGC 3532,
the Wishing Well Cluster.
More compact,
NGC 3766,
the Pearl Cluster, can be spotted at the left.
Anchoring the lower left of the cosmic canvas is another large
star-forming region,
IC 2948 with embedded
star cluster IC 2944.
That region is
popularly known as
the Running
Chicken Nebula.
Edge-on Spiral Galaxy NGC 891
Edge-on Spiral Galaxy NGC 891
This beautiful cosmic portrait
features NGC 891.
The spiral galaxy
spans about 100 thousand light-years and is seen almost exactly edge-on
from our perspective.
In fact, about 30 million light-years distant in the constellation
Andromeda,
NGC 891 looks a lot
like our Milky Way.
At first glance, it has a
flat, thin, galactic disk and
a central bulge cut along the middle by
regions of dark obscuring dust.
Also apparent in NGC 891's
ege-on presentation are filaments
of dust
that extend hundreds of
light-years above and below the center line.
The dust has likely been blown out of the disk
by supernova explosions or intense
star formation activity.
Faint neighboring galaxies can also been seen near this galaxy's disk.
Astronaut Installs Panoramic Space Window
Astronaut Installs Panoramic Space Window
This space job was almost complete.
Floating just below the
International Space Station, astronaut
Nicholas Patrick put some
finishing touches on the newly installed
cupola space windows last week.
Patrick was a
mission specialist onboard the recently completed
space shuttle
Endeavor's STS-130 mission to the ISS.
Pictured, Patrick floats near the outermost of seven windows on the
new cupola of the just-installed
Tranquility module.
Patrick hovers about 340 kilometers
over the Earth's surface, well in front of the blue sky, blue water, and white clouds pictured far in the background.
In the
above image, covers on windows
three and
four were in place and clearly labelled.
Images from
inside the
ISS's new panoramic
cupola are now
available.
Exceptional Rocket Waves Destroy Sun Dog
Exceptional Rocket Waves Destroy Sun Dog
What created those rocket waves, and why did they destroy that sun dog?
Close inspection of the
above image shows not only a rocket rising near the center, but unusual air ripples around it and a colorful sundog to the far right.
The rocket, carrying the
Solar Dynamics Observatory (SDO), lifted off two weeks ago from
Cape
Canaveral,
Florida,
USA into a cold blue sky.
The SDO is designed to observe the Sun continuously over the next several years,
exploring the
Sun's atmosphere
at high resolution and fast time scales.
The air ripples -- seen about one minute after launch -- were unexpected,
as was the sudden disappearance of the
sundog after the ripples passed.
Noticed and recorded by
several
onlookers, there has been much speculation about the origin of
the ripples.
An ongoing discussion about them can be joined
here in APOD's discussion board
the Asterisk.
A leading hypothesis holds that the ripples resulted from a
sonic boom created as the rocket broke the
sound barrier,
which then jumbled a thin layer of
ice crystals
that were aligned to create the
sundog.
Lingering questions include why
other rocket launches
don't produce air ripples as noticeable,
and why the ripples appeared more prominent above the rocket.
If you know of images of any other
aircraft or
spacecraft that have produced similar air ripples, please post them to
the discussion thread -- they may be
help create a better understanding of the effect.
Galaxy Group Hickson 31
Galaxy Group Hickson 31
Will the result of these galactic collisions be one big
elliptical galaxy?
Quite possibly, but not for
another billion years.
Pictured above, several of the
dwarf galaxies of in the
Hickson
Compact Group 31 are seen slowly merging.
Two of the brighter galaxies are colliding on the far left, while an
elongated galaxy above is connected to them by an unusual bridge of stars.
Inspection of the above image further indicates that the bright duo trail a rope of stars pointing to the
spiral galaxy on the far right.
Most assuredly, the pictured galaxies of Hickson Compact Group 31 will pass through and destroy each other, millions of stars will form and
explode, and thousands of nebula will
form and dissipate before the
dust
settles and the final galaxy emerges about one billion years from now.
The above image is a composite of images taken in
infrared light by the
Spitzer Space Telescope,
ultraviolet light
by the GALEX space telescope, and
visible light
by the Hubble Space Telescope.
Hickson Compact Group 31 spans about 150 thousand
light years and lies about 150 million light years away toward the constellation of
Eridanus.
NGC 2440: Cocoon of a New White Dwarf
NGC 2440: Cocoon of a New White Dwarf
Like a butterfly, a white dwarf star begins its life
by casting off a
cocoon that enclosed its former self.
In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all!
In the above cocoon, the planetary nebula designated
NGC 2440, contains one of the
hottest white dwarf stars known.
The white dwarf can be seen as the bright dot near the photo's center.
Our Sun will eventually become a
white dwarf
butterfly but not for another 5 billion years.
The above false color image was post-processed by Forrest Hamilton.
Geostationary Highway
Geostationary Highway
Put a satellite
in a circular orbit about 42,000 kilometers from the
center of the Earth (36,000 kilometers or so above the surface)
and it will orbit once in 24 hours.
Because that matches Earth's rotation period, it is known as
a geosynchronous orbit.
If that orbit is also in the plane of the equator,
the satellite will hang in the sky over a fixed location in
a
geostationary orbit.
As predicted in the 1940s by futurist
Arthur C. Clark,
geostationary
orbits are in common use
for communication and weather satellites,
a scenario now well-known to astroimagers.
Deep images of the night sky made with telescopes that follow
the stars can also
pick up geostationary
satellites glinting in sunlight still shining
far above the Earth's surface.
Because they all move with the Earth's rotation against the
background of stars, the satellites leave trails that
seem to follow a highway across the celestial landscape.
For example, in this wide view of the nearly equatorial
Orion region,
individual frames were added to create a 10 minute long exposure.
It shows Orion's belt stars and
well-known nebulae along with many
2.5 degree long geostationary satellite trails.
The frames are from an ingenious movie, featuring the
geostationary
satellite highway.