Sunday, April 12, 2015

This Mountain on Mars Is Leaking

This Mountain on Mars Is Leaking:



Seasonal flows spotted by HiRISE on northwestern slopes in Hale Crater. (NASA/JPL/University of Arizona)


Seasonal flows spotted by HiRISE on northwestern slopes in Hale Crater. (NASA/JPL/University of Arizona)
As the midsummer Sun beats down on the southern mountains of Mars, bringing daytime temperatures soaring up to a balmy 25ºC (77ºF), some of their slopes become darkened with long, rusty stains that may be the result of water seeping out from just below the surface.

The image above, captured by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter on Feb. 20, shows mountain peaks within the 150-km (93-mile) -wide Hale Crater. Made from data acquired in visible and near infrared wavelengths the long stains are very evident, running down steep slopes below the rocky cliffs.

These dark lines, called recurring slope lineae (RSL) by planetary scientists, are some of the best visual evidence we have of liquid water existing on Mars today – although if RSL are the result of water it’s nothing you’d want to fill your astro-canteen with; based on the first appearances of these features in early Martian spring any water responsible for them would have to be extremely high in salt content.

According to HiRISE Principal Investigator Alfred McEwen “[t]he RSL in Hale have an unusually “reddish” color compared to most RSL, perhaps due to oxidized iron compounds, like rust.”

See a full image scan of the region here, and watch an animation of RSL evolution (in another location) over the course of a Martian season here.



Perspective view of Hale crater made from data acquired by ESA's Mars Express. Credit: ESA/DLR/FU Berlin (G. Neukum)


Perspective view of Hale crater made from data acquired by ESA’s Mars Express. Credit: ESA/DLR/FU Berlin (G. Neukum)


Channels in the southeastern ejecta of Hale crater. Credit: NASA/JPL-Caltech/Arizona State University. (Source.)


THEMIS image of channels in the southeastern ejecta of Hale crater. Credit: NASA/JPL-Caltech/Arizona State University. (Source.)
Hale Crater itself is likely no stranger to liquid water. Its geology strongly suggests the presence of water at the time of its formation at least 3.5 billion years ago in the form of subsurface ice (with more potentially supplied by its cosmic progenitor) that was melted en masse at the time of impact. Today carved channels and gullies branch within and around the Hale region, evidence of enormous amounts of water that must have flowed from the site after the crater was created. (Source.)

The crater is named after George Ellery Hale, an astronomer from Chicago who determined in 1908 that sunspots are the result of magnetic activity.

Read more on the University of Arizona’s HiRISE site here.

Sources: NASA, HiRISE and Alfred McEwen



About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

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Venus in the West

Venus in the West: APOD: 2015 April 11 - Venus in the West


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2015 April 11



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Explanation: In the coming days, Venus shines near the western horizon at sunset. To find Earth's sister planet in twilight skies just look for the brilliant evening star. Tonight very close to the Pleiades star cluster, Venus dominates this springtime night skyscape taken only a few days ago near the town of Lich in central Germany. Also known as the Seven Sisters, the stars of the compact Pleiades cluster appear above Venus in this picture. The budding tree branches to its left frame bright star Aldebaran, the eye of Taurus the Bull, and the V-shaped Hyades star cluster.

Saturday, April 11, 2015

Roll Cloud Over Wisconsin

Roll Cloud Over Wisconsin: APOD: 2013 September 8 - Roll Cloud Over Wisconsin


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2013 September 8


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Explanation: What kind of cloud is this? A type of arcus cloud called a roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud. When this happens uniformly along an extended front, a roll cloud may form. Roll clouds may actually have air circulating along the long horizontal axis of the cloud. A roll cloud is not thought to be able to morph into a tornado. Unlike a similar shelf cloud, a roll cloud is completely detached from their parent cumulonimbus cloud. Pictured above, a roll cloud extends far into the distance as a storm approached in 2007 in Racine, Wisconsin, USA.

Nearby Cepheid Variable RS Pup

Nearby Cepheid Variable RS Pup: APOD: 2013 September 9 - Nearby Cepheid Variable RS Pup


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2013 September 9


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Explanation: It is one of the most important stars in the sky. This is partly because, by coincidence, it is surrounded by a dazzling reflection nebula. Pulsating RS Puppis, the brightest star in the image center, is some ten times more massive than our Sun and on average 15,000 times more luminous. In fact, RS Pup is a Cepheid type variable star, a class of stars whose brightness is used to estimate distances to nearby galaxies as one of the first steps in establishing the cosmic distance scale. As RS Pup pulsates over a period of about 40 days, its regular changes in brightness are also seen along the nebula delayed in time, effectively a light echo. Using measurements of the time delay and angular size of the nebula, the known speed of light allows astronomers to geometrically determine the distance to RS Pup to be 6,500 light-years, with a remarkably small error of plus or minus 90 light-years. An impressive achievement for stellar astronomy, the echo-measured distance also more accurately establishes the true brightness of RS Pup, and by extension other Cepheid stars, improving the knowledge of distances to galaxies beyond the Milky Way. The above image was taken by the Hubble Space Telescope and digitally processed by a volunteer.

Extrasolar Super Earth Gliese 1214b Might Hold Water

Extrasolar Super Earth Gliese 1214b Might Hold Water: APOD: 2013 September 10 - Extrasolar Super Earth Gliese 1214b Might Hold Water


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2013 September 10
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Extrasolar Super-Earth Gliese 1214b Might Hold Water

Illustration Credit & License: ESO, L. Calçada
Explanation: Might this distant planet hold water? Actually, given how close Gliese 1214b is to its parent star, any water, if it exists, would surely be in the form of steam. In the above artist's illustration, the super-Earth Gliese 1214b is imagined passing in front of its parent star, creating a mini-eclipse that alerted humanity to its presence. Gliese 1214b, also designated GJ 1214b, has been designated a super-Earth because it is larger than the Earth but smaller a planet like Neptune. The entire Gliese 1214 planetary system is of the closest known systems to our Sun, located only 42 light years away. The parent star, Gliese 1214 is a slightly smaller and cooler version of our Sun. Recent observations from the Subaru telescope in Hawaii found very little scattering of blue light from the parent star by the planet. This appears most consistent with a planet that has a watery atmosphere -- although it is still possible that the super-Earth has clouds so thick that little of any color of light was scattered. Detecting water on exoplanets is important partly because most lifeforms on Earth need water to survive.

LADEE Launch Streak

LADEE Launch Streak: APOD: 2013 September 11 - LADEE Launch Streak


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2013 September 11


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Explanation: On September 6, a starry night and the Milky Way witnessed the launch of a Minotaur V rocket from NASA's Wallops Flight Facility on Wallops Island, Virginia. So did a large part of the eastern United States, as the spectacular night launch was easily visible even from light polluted urban areas. This 35 second exposure captures part of the rocket's initial launch streak and 2nd stage ignition flare along with a fiery reflection in calm waters. The stunning view faces south and west from a vantage point overlooking Sinepuxent Bay in Maryland about 20 miles north of the launch pad. Heading east over the Atlantic, the multi-stage rocket placed LADEE, the Lunar Atmosphere and Dust Environment Explorer, into a highly elliptical Earth orbit to begin its journey to the Moon.

Stars and Dust Across Corona Australis

Stars and Dust Across Corona Australis: APOD: 2013 September 12 - Stars and Dust Across Corona Australis


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2013 September 12


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Explanation: Cosmic dust clouds sprawl across a rich field of stars in this sweeping telescopic vista near the northern boundary of Corona Australis, the Southern Crown. Less than 500 light-years away the dust clouds effectively block light from more distant background stars in the Milky Way. The entire frame spans about 2 degrees or over 15 light-years at the clouds' estimated distance. Near center is a group of lovely reflection nebulae cataloged as NGC 6726, 6727, 6729, and IC 4812. A characteristic blue color is produced as light from hot stars is reflected by the cosmic dust. The dust also obscures from view stars in the region still in the process of formation. Smaller yellowish nebula NGC 6729 surrounds young variable star R Coronae Australis. Below it are arcs and loops identified as Herbig Haro objects associated with energetic newborn stars. Magnificent globular star cluster NGC 6723 is at the right. Though NGC 6723 appears to be part of the group, its ancient stars actually lie nearly 30,000 light-years away, far beyond the young stars of the Corona Australis dust clouds.

Crescent Moon Meets Evening Star

Crescent Moon Meets Evening Star: APOD: 2013 September 13 - Crescent Moon Meets Evening Star


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2013 September 13


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Crescent Moon Meets Evening Star

Image Credit & Copyright: Luis Argerich, Agustin Llorens, Guido Medici, Gabriel Remotti
Explanation: On September 8, brilliant planet Venus appearing as the evening star stood near a slender, crescent Moon at sunset. The close celestial pairing or conjunction was a scene enjoyed by skygazers around the world. But from some locations in South America, the Moon actually passed in front of Venus in a lunar occultation. Captured near Las Cañas, Uruguay, this two frame mosaic telescopic view shows the Moon and Venus before and after the occultation. The silvery evening star appears at right just before it winked out behind the dark lunar limb, still in bright twilight skies. About an hour later Venus emerged (left) along the three day old Moon's sunlit edge.

A Landing on Planet Earth

A Landing on Planet Earth: APOD: 2013 September 14 - A Landing on Planet Earth


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2013 September 14


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A Landing on Planet Earth

Image Credit: NASA, Bill Ingalls
Explanation: With parachute deployed and retro-rockets blazing, this spacecraft landed on planet Earth on September 11 (UT) in a remote area near the town of Zhezkazgan, Kazakhstan. Seen in silhouette against the rockets' glare, the spacecraft is a Soyuz TMA-08M. Its crew, Expedition 36 Commander Pavel Vinogradov and Flight Engineer Alexander Misurkin of the Russian Federal Space Agency (Roscosmos), and Flight Engineer Chris Cassidy of NASA were returning after five and half months aboard the International Space Station. The Soyuz retro-rockets fire very quickly and for an extremely short duration near touchdown. Capturing the moment, the well-timed photograph was taken from a helicopter flying over the landing site.

M2 9: Wings of a Butterfly Nebula

M2 9: Wings of a Butterfly Nebula: APOD: 2013 September 15 - M2 9: Wings of a Butterfly Nebula


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2013 September 15


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Explanation: Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays as they die. In the case of low-mass stars like our Sun and M2-9 pictured above, the stars transform themselves from normal stars to white dwarfs by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula that fades gradually over thousand of years. M2-9, a butterfly planetary nebula 2100 light-years away shown in representative colors, has wings that tell a strange but incomplete tale. In the center, two stars orbit inside a gaseous disk 10 times the orbit of Pluto. The expelled envelope of the dying star breaks out from the disk creating the bipolar appearance. Much remains unknown about the physical processes that cause planetary nebulae.

Galaxy Cluster Abell 1689 Deflects Light

Galaxy Cluster Abell 1689 Deflects Light: APOD: 2013 September 17 - Galaxy Cluster Abell 1689 Deflects Light


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2013 September 17


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Explanation: It is one of the most massive objects in the visible universe. In this view from the Hubble Space Telescope's Advanced Camera for Surveys, Abell 1689 is seen to warp space as predicted by Einstein's theory of gravity -- deflecting light from individual galaxies which lie behind the cluster to produce multiple, curved images. The power of this enormous gravitational lens depends on its mass, but the visible matter, in the form of the cluster's yellowish galaxies, only accounts for about one percent of the mass needed to make the observed bluish arcing images of background galaxies. In fact, most of the gravitational mass required to warp space enough to explain this cosmic scale lensing is in the form of still mysterious dark matter. As the dominant source of Abell 1689's gravity, the dark matter's unseen presence is mapped out by the lensed arcs and distorted background galaxy images. Surprisingly, close inspection of the above image has revealed the presence of over 100,000 globular star clusters in the galaxy cluster.

M45: The Pleiades Star Cluster

M45: The Pleiades Star Cluster: APOD: 2013 September 18 - M45: The Pleiades Star Cluster


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2013 September 18


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Explanation: Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as dusty as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The above exposure took about 20 minutes and covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye. The actual number of Pleiades stars visible, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer's eyesight.

YES Moon, Venus, and Planet Earth

Moon, Venus, and Planet Earth: APOD: 2013 September 19 - Moon, Venus, and Planet Earth


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2013 September 19


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Explanation: In this engaging scene from planet Earth, the Moon shines through cloudy skies following sunset on the evening of September 8. Despite the fading light, the camera's long exposure still recorded a colorful, detailed view of a shoreline and western horizon looking toward the island San Gabriel from Colonia del Sacramento, Uruguay. Lights from Buenos Aires, Argentina are along the horizon on the left, across the broad Rio de la Plata estuary. The long exposure strongly overexposed the Moon and sky around it, though. So the photographer quickly snapped a shorter one to merge with the first image in the area around the bright lunar disk. As the the second image was made with a telephoto setting, the digital merger captures both Earth and sky, exaggerating the young Moon's slender crescent shape in relation to the two nearby bright stars. The more distant is bluish Spica, alpha star of the constellation Virgo. Closest to the Moon is Earth's evening star, planet Venus, emerging from a lunar occultation.

Night at the Drive-in

Night at the Drive-in: APOD: 2013 September 20 - Night at the Drive-in


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2013 September 20
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Explanation: Colorful stars trail through this late summer, night skyscape from Cape Cod, Massachusetts. The picture was composed by stacking 12 consecutive 1 minute long digital camera exposures to follow the trails, a reflection of our fair planet's daily rotation. It also records faint clouds of the Milky Way in the clear sky, stretching above a local drive-in movie theater. In fact, watching movies from cars at the drive-in was once a more common night time activity. But while the stars still shine, drive-in theaters have faded from the American landscape over the decades since the 1950s. Still, this recent scene includes a short exposure made as the projector beamed a space age image to the movie screen, and drive-in skygazers watched a view of the Earth below the International Space Station, under the stars above.

Antares Rocket Launch

Antares Rocket Launch: APOD: 2013 September 21 - Antares Rocket Launch


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2013 September 21


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Antares Rocket Launch

Image Credit: NASA, Bill Ingalls
Explanation: The sky looks dark in this scene from the Mid-Atlantic Regional Spaceport (MARS) at NASA Wallops Flight Facility, Virginia. Captured on Wednesday, September 18, an Orbital Sciences Corporation Antares rocket is leaving launch pad-0A with the Cygnus cargo spacecraft aboard. Though it looks like night, the photograph was taken at 10:58am EDT, under bright, clear morning skies, with a digital camera modified to record infrared images. The Sun itself is above and left of the picture frame, creating strong glare and internal reflections in the camera lens at near-infrared wavelengths. In the false-color presentation, the vegetation and watery reflections also take on an otherworldly pallor. Reaching orbit, the Cygnus spacecraft is now on its way to a Sunday rendezvous with the International Space Station. The spacecraft will deliver about 1,300 pounds (589 kilograms) of cargo to the Expedition 37 crew.

Apollo s Analemma

Apollo s Analemma: APOD: 2013 September 22 - Apollo's Analemma


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2013 September 22


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Explanation: Today, the Sun crosses the celestial equator heading south at 20:44 Universal Time. An equinox (equal night), this astronomical event marks the first day of autumn in the northern hemisphere and spring in the south. With the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. To celebrate, consider this remarkable record of the Sun's yearly journey through planet Earth's sky, made with planned multiple exposures captured on a single piece of 35 millimeter film. Exposures were made at the same time of day (9:00am local time), capturing the Sun's position on dates from January 7 through December 20, 2003. The multiple suns trace an intersecting curve known as an analemma. A foreground base exposure of the Temple of Apollo in ancient Corinth, Greece, appropriate for an analemma, was digitally merged with the film image. Equinox dates correspond to the middle points (not the intersection point) of the analemma. The curve is oriented at the corresponding direction and altitude for the temple, so the Sun's position for the September equinox is at the upper midpoint near picture center. Summer and winter solstices are at analemma top and bottom.

IC 4628: The Prawn Nebula

IC 4628: The Prawn Nebula: APOD: 2013 September 23 - IC 4628: The Prawn Nebula


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2013 September 23


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Explanation: South of Antares, in the tail of the nebula-rich constellation Scorpius, lies emission nebula IC 4628. Nearby hot, massive stars, millions of years young, radiate the nebula with invisible ultraviolet light, stripping electrons from atoms. The electrons eventually recombine with the atoms to produce the visible nebular glow, dominated by the red emission of hydrogen. At an estimated distance of 6,000 light-years, the region shown is about 250 light-years across, spanning an area equivalent to four full moons on the sky. The nebula is also cataloged as Gum 56 for Australian astronomer Colin Stanley Gum, but seafood-loving astronomers might know this cosmic cloud as The Prawn Nebula.

The Local Fluff

The Local Fluff: APOD: 2013 September 24 - The Local Fluff


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2013 September 24


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Explanation: The stars are not alone. In the disk of our Milky Way Galaxy about 10 percent of visible matter is in the form of gas, called the interstellar medium (ISM). The ISM is not uniform, and shows patchiness even near our Sun. It can be quite difficult to detect the local ISM because it is so tenuous and emits so little light. This mostly hydrogen gas, however, absorbs some very specific colors that can be detected in the light of the nearest stars. A working map of the local ISM within 20 light-years, based on ongoing observations and recent particle detections from the Earth-orbiting Interstellar Boundary Exporer satellite (IBEX), is shown above. These observations indicate that our Sun is moving through a Local Interstellar Cloud as this cloud flows outwards from the Scorpius-Centaurus Association star forming region. Our Sun may exit the Local Cloud, also called the Local Fluff, during the next 10,000 years. Much remains unknown about the local ISM, including details of its distribution, its origin, and how it affects the Sun and the Earth. Unexpectedly, recent IBEX spacecraft measurements indicate that the direction from which neutral interstellar particles flow through our Solar System is changing.

M81 versus M82

M81 versus M82: APOD: 2013 September 25 - M81 versus M82


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2013 September 25
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Explanation: Here in the Milky Way galaxy we have astronomical front row seats as M81 and M82 face-off, a mere 12 million light-years away. Locked in a gravitational struggle for the past billion years or so, the two bright galaxies are captured in this deep telescopic snapshot, constructed from 25 hours of image data. Their most recent close encounter likely resulted in the enhanced spiral arms of M81 (left) and violent star forming regions in M82 so energetic the galaxy glows in X-rays. After repeated passes, in a few billion years only one galaxy will remain. From our perspective, this cosmic moment is seen through a foreground veil of the Milky Way's stars and clouds of dust. Faintly reflecting the foreground starlight, the pervasive dust clouds are relatively unexplored galactic cirrus, or integrated flux nebulae, only a few hundred light-years above the plane of the Milky Way.

M31 versus M33

M31 versus M33: APOD: 2013 September 26 - M31 versus M33


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2013 September 26


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Explanation: Separated by about 14 degrees (28 Full Moons) in planet Earth's sky, spiral galaxies M31, left, and M33 are both large members of the Local Group, along with our own Milky Way galaxy. This wide-angle, telescopic mosaic captures colorful details of spiral structure in both, while the massive neighboring galaxies seem to be balanced either side of bright Mirach, beta star in the constellation Andromeda. But M31, the Andromeda Galaxy, is really 2.5 million light-years distant and M33, the Triangulum Galaxy, is also about 3 million light years away. Mirach, just 200 light-years from the Sun, lies well within the Milky Way, along with the dim clouds of dust drifting through the frame only a few hundred light-years above the galactic plane. Although they look far apart, M31 and M33 are locked in a mutual gravitational embrace. Radio astronomers have found indications of a bridge of neutral hydrogen gas that could connect the two, evidence of a closer encounter in the past. Based on measurements, gravitational simulations currently predict that the Milky Way, M31, and M33 will all undergo mutual close encounters and potentially mergers, billions of years in the future.

Andromeda on the Rocks

Andromeda on the Rocks: APOD: 2013 September 27 - Andromeda on the Rocks


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2013 September 27


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Explanation: How far can you see? The Andromeda Galaxy 2.5 million light years away is the most distant object easily seen by the unaided eye. Other apparent denizens of the night sky, stars, clusters, and nebulae, typically range from a few hundred to a few thousand light-years away and lie well within our own Milky Way Galaxy. Also known as M31, the Andromeda Galaxy is the faint smudge near top center of this Earth and skyscape, taken from eastern Italy, near Monte Conero on the Adriatic sea coast. From a few centimeters to a few million light-years, the picture demonstrates a stunning range of vision. Though galaxy and seaside rocks could be seen with the eye on that clear summer night, no camera captured this view in a single exposure. Because the stars trailed above the horizon while the picture was made, separate exposures tracking the stars were combined with one of rocks and cliffs made with the camera steadied to create the tantalizing scene.

Equinox Earth

Equinox Earth: APOD: 2013 September 28 - Equinox Earth


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2013 September 28
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Explanation: From a geostationary orbit 36,000 kilometers above the equator, Russian meteorological satellite Elektro-L takes high-resolution images of our fair planet every 30 minutes. But only twice a year, during an Equinox, can it capture an image like this one, showing an entire hemisphere bathed in sunlight. At an Equinox, the Earth's axis of rotation is not tilted toward or away from the Sun, so the solar illumination can extend to both the planet's poles. Of course, this Elektro-L picture was recorded on September 22nd, at the northern hemisphere's autumnal equinox. For a moment on that date, the Sun was behind the geostationary satellite and a telltale glint of reflected sunlight is seen crossing the equator, at the location on the planet with satellite and sun directly overhead (5MB animated gif).

The Fairy of Eagle Nebula

The Fairy of Eagle Nebula:



The dust sculptures of the Eagle Nebula are evaporating

Explanation: The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Pictured above is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula, M16, is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. The above image in scientifically re-assigned colors was released in 2005 as part of the fifteenth anniversary celebration of the launch of the Hubble Space Telescope..




Three Galaxies in Draco

Three Galaxies in Draco: APOD: 2013 October 16 - Three Galaxies in Draco


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2013 October 16


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Explanation: This intriguing trio of galaxies is sometimes called the Draco Group, located in the northern constellation of (you guessed it) Draco. From left to right are edge-on spiral NGC 5981, elliptical galaxy NGC 5982, and face-on spiral NGC 5985 -- all within this single telescopic field of view spanning a little more than half the width of the full moon. While the group is far too small to be a galaxy cluster and has not been catalogued as a compact group, these galaxies all do lie roughly 100 million light-years from planet Earth. On close examination with spectrographs, the bright core of the striking face-on spiral NGC 5985 shows prominent emission in specific wavelengths of light, prompting astronomers to classify it as a Seyfert, a type of active galaxy. Not as well known as other tight groupings of galaxies, the contrast in visual appearance makes this triplet an attractive subject for astrophotographers. This impressively deep exposure hints at faint, sharp-edged shells surrounding elliptical NGC 5982, evidence of past galactic mergers. It also reveals many even more distant background galaxies.