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Aurora Over Yellowknife

Astronomy Picture of the Day - Dm, 22/09/2009 - 13:10

Aurora Over Yellowknife
Credit & Copyright: Yuichi Takasaka (Blue Moon Promotions), TWAN

Explanation: Sometimes, after your eyes adapt to the dark, a spectacular sky appears. In this case, a picturesque lake lies in front of you, beautiful green auroras flap high above you, brilliant stars shine far in the distance, and a brilliant moon shines just ahead of you. This digitally fused panorama was captured earlier this month from Yellowknife, Northwest Territories, Canada, and includes the Pleiades open cluster of stars just to the upper right of the Moon. Since aurora are ultimately started by solar activity, this current flurry of aurora is somewhat surprising, given the historic lack of sunspots and other activity on the Sun over the past two years. This time of year is known as aurora season, however, for noted average increases in auroras. The reason for the yearly increase is not known for sure, but possibly relates to the tilt of the Earth creating a more easily traversable connection between the Earth's magnetic field and the magnetic field of the Sun's changing wind streams.

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Abell 370: Galaxy Cluster Gravitational Lens

Astronomy Picture of the Day - Dll, 21/09/2009 - 11:10

Abell 370: Galaxy Cluster Gravitational Lens
Credit: NASA, ESA, and the Hubble SM4 ERO Team & ST-ECF

Explanation: What is that strange arc? While imaging the cluster of galaxies Abell 370, astronomers had noted an unusual arc to the right of many cluster galaxies. Although curious, one initial response was to avoid commenting on the arc because nothing like it had ever been noted before. In the mid-1980s, however, better images allowed astronomers to identify the arc as a prototype of a new kind of astrophysical phenomenon -- the gravitational lens effect of entire cluster of galaxies on background galaxies. Today, we know that this arc actually consists of two distorted images of a fairly normal galaxy that happened to lie far behind the huge cluster. Abell 370's gravity caused the background galaxies' light -- and others -- to spread out and come to the observer along multiple paths, not unlike a distant light appears through the stem of a wine glass. In mid-July, astronomers used the just-upgraded Hubble Space Telescope to image Abell 370 and its gravitational lens images in unprecedented detail. Almost all of the yellow images pictured above are galaxies in the Abell 370 cluster. An astute eye can pick up many strange arcs and distorted arclets, however, that are actually images of more distant galaxies. Studying Abell 370 and its images gives astronomers a unique window into the distribution of normal and dark matter in galaxy clusters and the universe.

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Ganymede Enhanced

Astronomy Picture of the Day - Dg, 20/09/2009 - 09:10

Ganymede Enhanced
Credit: Galileo Project, DLR, JPL, NASA

Explanation: What does the largest moon in the Solar System look like? Ganymede, larger than even Mercury and Pluto, has a surface speckled with bright young craters overlying a mixture of older, darker, more cratered terrain laced with grooves and ridges. Like Earth's Moon, Ganymede keeps the same face towards its central planet, in this case Jupiter. In this historic and detailed image mosaic taken by the Galileo spacecraft that orbited Jupiter from 1995 to 2003, the colors of this planet-sized moon have been enhanced to increase surface contrasts. The violet shades extending from the top and bottom are likely due to frost particles in Ganymede's polar regions. Possible future missions to Jupiter are being proposed that can search Europa and Ganymede for deep oceans that may harbor elements thought important for supporting life.

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NGC 3621: Far Beyond the Local Group

Astronomy Picture of the Day - Ds, 19/09/2009 - 20:10

NGC 3621: Far Beyond the Local Group
Credit & Copyright: Robert Gendler

Explanation: Far beyond the local group of galaxies lies NGC 3621, some 22 million light-years away. Found in the multi-headed southern constellation Hydra, the winding spiral arms of this gorgeous island universe are loaded with luminous young star clusters and dark dust lanes. Still, for earthbound astronomers NGC 3621 is not just another pretty face-on spiral galaxy. Some of its brighter stars have been used as standard candles to establish important estimates of extragalactic distances and the scale of the Universe. This beautiful image of NGC 3621 traces the loose spiral arms far from the galaxy's brighter central regions that span some 100,000 light-years. Spiky foreground stars in our own Milky Way Galaxy and even more distant background galaxies are scattered across the colorful skyscape.

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Take My Hand

Astronomy Picture of the Day - Dv, 18/09/2009 - 18:10

Take My Hand
Credit: NASA / STS-128 / Expedition 20 - Stereo Image by Patrick Vantuyne

Explanation: Get out your red/blue glasses and check out this close-up of spacesuited NASA astronaut John Olivas outside the International Space Station. Carefully constructed from two photographs (ISS020-E-038481, ISS02-0E-038482) taken during space shuttle orbiter Discovery's latest visit to the orbiting outpost, the 3D anaglyph creates the compelling illusion that you can actually reach out and take his gloved hand. The photographer, fellow spacewalker ESA astronaut Christer Fuglesang, along with ISS structures and planet Earth's horizon, are reflected in Olivas' helmet visor. Last Friday, the two returned to Earth along with the rest of Discovery's crew, landing at Edwards Air Force base in California.

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Ultraviolet Andromeda

Astronomy Picture of the Day - Dj, 17/09/2009 - 16:10

Ultraviolet Andromeda
Credit: UV - NASA/Swift/Stefan Immler (GSFC) and Erin Grand (UMCP)
Optical - Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF

Explanation: Taken by a telescope onboard NASA's Swift satellite, this stunning vista represents the highest resolution image ever made of the Andromeda Galaxy (aka M31) - at ultraviolet wavelengths. The mosaic is composed of 330 individual images covering a region 200,000 light-years wide. It shows about 20,000 sources, dominated by hot, young stars and dense star clusters that radiate strongly in energetic ultraviolet light. Of course, the Andromeda Galaxy is the closest large spiral galaxy to our own Milky Way, at a distance of some 2.5 million light-years. To compare this gorgeous island universe's appearance in optical light with its ultraviolet portrait, just slide your cursor over the image.

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The Tarantula Zone

Astronomy Picture of the Day - Dc, 16/09/2009 - 14:10

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.

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NGC 6888: The Crescent Nebula

Astronomy Picture of the Day - Dm, 15/09/2009 - 12:10

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.

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The Holographic Principle

Astronomy Picture of the Day - Dg, 13/09/2009 - 17:10

The Holographic Principle
Credit & Copyright: E. Winfree, K. Fleischer, A. Barr et al. (Caltech)

Explanation: Is this picture worth a thousand words? According to the Holographic Principle, the most information you can get from this image is about 3 x 1065 bits for a normal sized computer monitor. The Holographic Principle, yet unproven, states that there is a maximum amount of information content held by regions adjacent to any surface. Therefore, counter-intuitively, the information content inside a room depends not on the volume of the room but on the area of the bounding walls. The principle derives from the idea that the Planck length, the length scale where quantum mechanics begins to dominate classical gravity, is one side of an area that can hold only about one bit of information. The limit was first postulated by physicist Gerard 't Hooft in 1993. It can arise from generalizations from seemingly distant speculation that the information held by a black hole is determined not by its enclosed volume but by the surface area of its event horizon. The term "holographic" arises from a hologram analogy where three-dimension images are created by projecting light though a flat screen. Beware, other people looking at the above image may not claim to see 3 x 1065 bits -- they might claim to see a teapot.

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Summer Night in Astronomy Town

Astronomy Picture of the Day - Dg, 13/09/2009 - 04:10

Summer Night in Astronomy Town
Credit & Copyright: Babak Tafreshi (TWAN)

Explanation: This serene view records a late summer night sky over the rolling, green hills of planet Earth. It was taken near the rural village of Saadat Shahr, Fars province, in southern Iran. Saadat Shahr is also known as Astronomy Town, as the inhabitants have demonstrated a remarkable passion for sky gazing. Fittingly, this Astronomy Town sky view finds a lovely part of the Milky Way near picture center. The three brightest stars are the stars of the Summer Triangle, Deneb in Cygnus (top), Altair in Aquila (left), and Vega in Lyra (right). The foreground landscape, illuminated by Astronomy Town lights, includes a kind of wild pistachio tree common in the region. To identify the stars and constellations, just slide your cursor over the image.

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Stephan's Quintet

Astronomy Picture of the Day - Dv, 11/09/2009 - 13:10

Stephan's Quintet
Credit: NASA, ESA, and the Hubble SM4 ERO Team

Explanation: The first identified compact galaxy group, Stephan's Quintet is featured in this stunning image from the newly upgraded Hubble Space Telescope. About 300 million light-years away, only four galaxies of the group are actually locked in a cosmic dance of repeated close encounters. The odd man out is easy to spot, though. The four interacting galaxies (NGC 7319, 7318A, 7318B, and 7317) have an overall yellowish cast and tend to have distorted loops and tails, grown under the influence of disruptive gravitational tides. But the bluish galaxy at the upper left (NGC 7320) is much closer than the others. A mere 40 million light-years distant, it isn't part of the interacting group. In fact, individual stars in the foreground galaxy can be seen in the sharp Hubble image, hinting that it is much closer than the others. Stephan's Quintet lies within the boundaries of the high flying constellation Pegasus.

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The Butterfly Nebula from Upgraded Hubble

Astronomy Picture of the Day - Dj, 10/09/2009 - 11:10

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. Above is a dramatically detailed close-up of the dying star's nebula recorded by the newly upgraded Hubble Space Telescope. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is in the upper right corner of this view, nearly edge-on to the line-of-sight. Molecular hydrogen has recently been detected in this hot star's dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation Scorpius.

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Star Trails Over Oregon

Astronomy Picture of the Day - Dc, 09/09/2009 - 09:10

Star Trails Over Oregon
Credit & Copyright: Joshua Bury

Explanation: As the Earth spins on its axis, the sky seems to rotate around us. This motion, called diurnal motion, produces the beautiful concentric trails traced by stars during time exposures. Partial-circle star trails are pictured above over Grants Pass, Oregon, USA last month. Near the middle of the circles is the North Celestial Pole (NCP), easily identified as the point in the sky at the center of all the star trail arcs. The star Polaris, commonly known as the North Star, made the very short bright circle near the NCP. About 12,000 years ago, the bright star Vega was the North Star, and in about 14,000 years, as the Earth's spin axis slowly continues to precess, Vega will become the North Star again.

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Unexpected Impact on Jupiter

Astronomy Picture of the Day - Dm, 08/09/2009 - 07:10

Unexpected Impact on Jupiter
Credit: ALPO, Theo Ramakers

Explanation: Two months ago, something unexpected hit Jupiter. First discovered by an amateur astronomer Anthony Wesley on 2009 July 19, the impact was quickly confirmed and even imaged by the Hubble Space Telescope the very next day. Many of the world's telescopes then zoomed in on our Solar System's largest planet to see the result. Some of these images have been complied into the above animation. Over the course of the last month and a half, the above time-lapse sequence shows the dark spot -- first created when Jupiter was struck -- deforming and dissipating as Jupiter's clouds churned and Jupiter rotated. It is now thought that a small comet -- perhaps less than one kilometer across -- impacted Jupiter on or before 2009 July 19. Although initially expected to be visible for only a week, astronomers continue to track atmospheric remnants of the impact for new information about winds and currents in Jupiter's thick atmosphere.

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Jupiter Over the Mediterranean

Astronomy Picture of the Day - Dll, 07/09/2009 - 18:10

Jupiter Over the Mediterranean
Credit & Copyright: Tunç Tezel (TWAN)

Explanation: This vacation included a sight to remember. Pictured above, a picturesque starscape capped a serene seascape as seen from Turkey this past August. In the above digitally stitched panorama, the Gelidonya Lighthouse shines in the foreground before a calm Mediterranean Sea. On the left, Jupiter is the brightest point in the image and since on the same side of the Sun as the Earth, was near its yearly brightest. Glowing just shy of magnitude -3, Jupiter was brighter than any star in the sky, and brighter even than Mars was during its famously bright opposition of 2003 August. On the right, the band of the Milky Way Galaxy fades into distant atmospheric haze above the horizon. Jupiter is nearing the closest part of its elliptical orbit to the Sun and so will appear even brighter during its next opposition in 2010 September.

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CMBR Dipole: Speeding Through the Universe

Astronomy Picture of the Day - Dll, 07/09/2009 - 05:10

CMBR Dipole: Speeding Through the Universe
Credit: DMR, COBE, NASA, Four-Year Sky Map

Explanation: Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group of Galaxies. The Local Group falls toward the Virgo Cluster of Galaxies. But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background radiation (CMBR). In the above all-sky map from the COBE satellite, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder. The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation. This high speed was initially unexpected and its magnitude is still unexplained. Why are we moving so fast? What is out there?

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Supernova Remnant E0102-72

Astronomy Picture of the Day - Ds, 05/09/2009 - 14:10

Supernova Remnant E0102-72
Credit: X-ray - NASA / CXC / MIT / D.Dewey et al., NASA / CXC / SAO / J.DePasquale;
Optical - NASA / STScI

Explanation: The expanding debris cloud from the explosion of a massive star is captured in this multiwavelength composite, combining x-ray and optical images from the Chandra and Hubble telescopes. Identified as E0102-72, the supernova remnant lies about 190,000 light-years away in our neighboring galaxy, the Small Magellanic Cloud. A strong cosmic source of x-rays, E0102 was imaged by the Chandra X-ray Observatory shortly after its launch in 1999. In celebration of Chandra's 10th anniversary, this colorful view of E0102 and its environs was created, including additional Chandra data. An analysis of all the data indicates that the overall shape of E0102 is most likely a cylinder that is viewed end-on rather than a spherical bubble. The intriguing result implies that the massive star's explosion has produced a shape similar to what is seen in some planetary nebulae associated with lower mass stars. At the distance of the Small Magellanic Cloud, this field of view spans about 150 light-years.

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6 Years of Saturn

Astronomy Picture of the Day - Dv, 04/09/2009 - 12:10

6 Years of Saturn
Credit & Copyright: Alan Friedman

Explanation: Today, planet Earth passes through the plane of Saturn's rings. From the perspective of earthbound astronomers, Saturn's rings will be edge-on. The problem is, Saturn itself is now very close to the Sun, low on horizon after sunset, so good telescopic images will be difficult to come by. Still, this composite of Saturn views taken from 2004 - 2009 (lower right to upper left) illustrates the change in ring tilt over the last six years and includes a nearly edge-on ring view, based on images captured earlier this year. While Saturn's south pole is clearly seen in the sequence, particularly at the lower right, it will be hidden in the coming years. Saturn's north pole will be increasingly visible, along with the tilting rings, as the planet emerges this fall in the predawn sky.

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Despina, Moon of Neptune

Astronomy Picture of the Day - Dj, 03/09/2009 - 10:10

Despina, Moon of Neptune
Credit: NASA, JPL, Ted Stryk

Explanation: Despina is a tiny moon of Neptune. A mere 148 kilometers across, diminutive Despina was discovered in 1989, in images from the Voyager 2 spacecraft taken during its encounter with the solar system's most distant gas giant planet. But looking through the Voyager 2 data 20 years later, amateur image processor (and philosophy professor) Ted Stryk discovered something no one had recognized before -- images that show the shadow of Despina in transit across Neptune's blue cloud tops. His composite view of Despina and its shadow is composed of four archival frames taken on August 24, 1989, separated by nine minutes. Despina itself has been artificially brightened to make it easier to see. In ancient Greek mythology, Despina is a daughter of Poseidon (the Roman god Neptune).

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Discovery's Rainbow

Astronomy Picture of the Day - Dc, 02/09/2009 - 21:10

Discovery's Rainbow
Credit: NASA, Ben Cooper (Launch Photography)

Explanation: Just one minute before midnight EDT, Friday, August 28, the Space Shuttle Discovery began a long arc into a cloudy sky. Following the launch, a bright and remarkably colorful trail was captured in this time exposure from the Banana River Viewing Site, looking east toward pad 39A at the Kennedy Space Center. On STS-128, Discovery docked with the International Space Station Sunday evening. The 13-day mission will exchange space station crew members and deliver more than 7 tons of supplies and equipment. Of course, the equipment includes the Combined Operational Load Bearing External Resistance Treadmill (COLBERT).

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