APOD Retrospective: March 14

A nostalgic look back at Astronomy Picture of the Day
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APOD Retrospective: March 14

Post by bystander » Wed Mar 14, 2012 3:30 am


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2015 Thursday, shortly after local sunrise over central Asia, this Soyuz spacecraft floated over a sea of golden clouds during its descent by parachute through planet Earth's dense atmosphere. On board were Expedition 42 commander Barry Wilmore of NASA and Alexander Samokutyaev and Elena Serova of the Russian Federal Space Agency (Roscosmos). Touch down was at approximately 10:07 p.m. EDT (8:07 a.m. March 12, Kazakh time) southeast of Zhezkazgan, Kazakhstan. The three were returning from low Earth orbit, after almost six months on the International Space Station as members of the Expedition 41 and Expedition 42 crews.

2014 NGC 2685 is a confirmed polar ring galaxy - a rare type of galaxy with stars, gas and dust orbiting in rings perpendicular to the plane of a flat galactic disk. The bizarre configuration could be caused by the chance capture of material from another galaxy by a disk galaxy, with the captured debris strung out in a rotating ring. Still, observed properties of NGC 2685 suggest that the rotating ring structure is remarkably old and stable. In this sharp view of the peculiar system also known as Arp 336 or the Helix galaxy, the strange, perpendicular rings are easy to trace as they pass in front of the galactic disk, along with other disturbed outer structures. NGC 2685 is about 50,000 light-years across and 40 million light-years away in the constellation Ursa Major.

2013 In silhouette against the colorful evening twilight, clouds part for this much anticipated magic moment. The scene captures naked-eye Comet PanSTARRS peeking into northern hemisphere skies on March 12. The comet stands over the western horizon after sunset, joined by the thin, flattened crescent of a day old Moon. Posing for its own beauty shot, the subtly lit dome of the 4.2 meter William Herschel Telescope is perched above cloud banks on the Canary Island of La Palma. While PanSTARRS has not quite developed into the spectacular comet once hoped for, it is still growing easier to see in the north. In coming days it will steadily climb north, farther from the Sun into darker western evening skies.

2012 It's one of the baddest sunspot regions in years. Active Region 1429 may not only look, to some, like an angry bird -- it has thrown off some of the most powerful flares and coronal mass ejections of the current solar cycle. The extended plumes from these explosions have even rained particles on the Earth's magnetosphere that have resulted in colorful auroras. Pictured above, AR 1429 was captured in great detail in the Sun's chromosphere three days ago by isolating a color of light emitted primarily by hydrogen. The resulting image is shown in inverted false color with dark regions being the brightest and hottest. Giant magnetically-channeled tubes of hot gas, some longer than the Earth, are known as spicules and can be seen carpeting the chromosphere. The light tendril just above AR 1429 is a cool filament hovering just over the active sunspot region. As solar maximum nears in the next few years, the increasingly wound and twisted magnetic field of the Sun may create even more furious active regions that chirp even more energetic puffs of solar plasma into our Solar System.

2011 Have you ever seen a "star" drifting slowly overhead, but not known what it was? Sometimes even pointing it out to friends or family will only lead to a shrug. What you are seeing, most likely, is a spacecraft in low Earth orbit reflecting back sunlight as it circles the Earth once every 90 minutes or so. Two of the brighter spacecraft in the present day sky are the International Space Station (ISS), and, when it is up, a NASA space shuttle. As relative orientations change, the brightness of reflections may also change, sometimes suddenly. Another source of bright drifting objects, Iridium communication satellites, may even appear to flare up to become brighter than any other sky object for a few seconds. Pictured above, two bright points of light separated by only a few degrees drifted together across the sky above Lory State Park, Colorado, USA last week, just after sunset. These lights were were the ISS and the space shuttle Discovery, which had undocked from the ISS a few hours earlier. Given a digital fusion of many separate camera exposures and a wide angle perspective, the pair appears above as streaks in front of point-like stars. Web sites now exist that can help you identify unknown "drifters" and even predict the time of the next pass of the ISS visible from your location.

2010 What's happening in the middle of this massive galaxy? There, two bright sources at the center of this composite x-ray (blue)/radio (pink) image are thought to be co-orbiting supermassive black holes powering the giant radio source 3C 75. Surrounded by multimillion degree x-ray emitting gas, and blasting out jets of relativistic particles the supermassive black holes are separated by 25,000 light-years. At the cores of two merging galaxies in the Abell 400 galaxy cluster they are some 300 million light-years away. Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets' consistent swept back appearance is most likely due to their common motion as they speed through the hot cluster gas at 1200 kilometers per second. Such spectacular cosmic mergers are thought to be common in crowded galaxy cluster environments in the distant universe. In their final stages the mergers are expected to be intense sources of gravitational waves.

2009 Fix your camera to a tripod and you can record the graceful trails traced by the stars as planet Earth rotates on its axis. For example, this dramatic 5 hour long exposure was made on February 24 from Haute-Provence Observatory (OHP) in southeastern France. Actually a composite of 300 consecutive 1-minute exposures, the image nicely shows stars near the celestial equator tracing nearly straight lines in projection, while stars north and south of the equator, respectively, appear to circle the north and south celestial poles. Domes at the bottom left and right house the OHP telescopes. Brilliant planet Venus makes the short bright trail at the lower right, while trails of stars in the constellation Orion end near the lower right observatory dome. Sirius, alpha star of Canis Major, traces the bright arc over the dome at the left. Astronomer Alexandre Santerne also briefly illuminated a foreground oak tree during the exposure sequence.

2008 Blasting into a dark night sky, the Space Shuttle Endeavour began its latest journey to orbit in the early morning hours of March 11. In this stunning picture following the launch, the glare from Endeavour's three main rocket engines and flanking solid fuel booster rockets illuminates the orbiter's tail section and the large, orange external fuel tank. Embarking on mission STS-123, Endeavour left Kennedy Space Center's pad 39A, ferrying a crew of seven astronauts to the International Space Station (ISS). The cargo included the first section of the Japan Aerospace Exploration Agency's Kibo laboratory and the Canadian Space Agency's two-armed robotic system. Astronauts will conduct a series of space walks to install the new equipment during the 16-day mission, the longest shuttle mission to the ISS.

2007 Why do some spiral galaxies have a ring around the center? First and foremost, M95 is one of the closer examples of a big and beautiful barred spiral galaxy. Visible in the above recent image from the CFHT telescope in Hawaii, USA, are sprawling spiral arms delineate by open clusters of bright blue stars, lanes of dark dust, the diffuse glow of billions of faint stars, and a short bar across the galaxy center. What intrigues many astronomers, however, is the circumnuclear ring around the galaxy center visible just outside the central bar. Recent images by the Chandra X-ray Observatory have shown that X-ray light surrounding the ring is likely emission from recent supernovas. Although the long term stability of the ring remains a topic of research, recent observations indicate its present brightness is at least enhanced by transient bursts of star formation. M95, also known as NGC 3351, spans about 50,000 light-years and can be seen with a small telescope toward the constellation of the Lion (Leo).

2006 Can a gas cloud eat a galaxy? It's not even close. The odd looking "creature" in the center of the above photo is a gas cloud known as a cometary globule. This globule, however, has ruptured. Cometary globules are typically characterized by dusty heads and elongated tails. These features cause cometary globules to have visual similarities to comets, but in reality they are very much different. Globules are frequently the birthplaces of stars, and many show very young stars in their heads. The reason for the rupture in the head of this object is not completely known. The galaxy to the left of center is huge, very far in the distance, and only placed near CG4 by chance superposition.

2005 The nebula surrounding bright star S Mon is filled with dark dust and glowing gas. The strange shapes originate from fine interstellar dust reacting in complex ways with the energetic light and hot gas being expelled by the young stars. The region just below S Mon, the brightest star in the above picture, is nicknamed the Fox Fur Nebula for its color and texture. The blue glow directly surrounding S Mon results from reflection, where neighboring dust reflects light from the bright star. The more diffuse red glow results from emission, where starlight ionizes hydrogen gas. Pink areas are lit by a combination of the two processes. S Mon is part of a young open cluster of stars named NGC 2264, located about 2500 light years away toward the constellation of Monoceros, just north of the Cone Nebula.

2004 Comet Hale-Bopp became much brighter than any surrounding stars. It was seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind struck expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours.

2003 Large, massive stars end their furious lives in spectacular supernova explosions -- but small, low mass stars may encounter a similar fate. In fact, instead of simply cooling off and quietly fading away, some white dwarf stars in binary star systems are thought to draw enough mass from their companions to become unstable, triggering a nuclear detonation. The resulting standard candle stellar explosion is classified as a Type Ia supernova and perhaps the best example yet of the aftermath is this expanding cloud of shocked stellar debris, DEM L71, in the nearby Large Magellanic Cloud. The sharp false-color x-ray image from the orbiting Chandra Observatory shows the predicted bright edges of the outer blast wave shock region and the x-ray glow of an inner region of reverse shock heated gas. Based on the Chandra data, estimates for the composition and total mass of expanding gas strongly suggest that this is all that remains of a white dwarf star. Light from this small star's self-destructive explosion would have first reached Earth several thousand years ago.

2002 Now complete, Servicing Mission 3B (SM3B) was really the fourth trip to the Hubble Space Telescope, as the originally planned mission 3 was split into two parts. Falling around planet Earth, about 320 nautical miles above the surface, the 13.2 meter long Great Observatory is pictured here in Space Shuttle Columbia's payload bay on March 5. Spacesuited astronaut Michael Massimino works under Hubble's "hood" while poised at the end of Columbia's Remote Manipulator System or robotic arm. Columbia's arm extends from the picture's right hand edge and a folded solar panel rests horizontally above Massimino's position. Dramatic backlighting is provided by a smiling sunlit crescent of Earth's atmosphere. SM3B supplied Hubble with a new camera, and substantial power and instrument upgrades which are presently being turned on and prepared for operation. The next Hubble service call, SM4, is planned for 2004.

2001 Outbound and climbing above the plane of our solar system, comet McNaught-Hartley (C/1999 T1) is presently soaring through northern skies. This telescopic picture, a composite of many 30 second exposures made through three color filters, recorded the delicate colors in its diminutive coma and faint tail on February 26th. Combining the exposures to produce the final image registered on the comet causes stars to appear as "dotted trails", evidence of the comet's motion relative to the distant stellar background. Discovered by southern hemisphere observers, this comet's closest approach to the Sun occurred in December last year as it passed just outside planet Earth's orbit. For now the brightest comet in the sky, this primordial chunk of solar system is crossing from the constellation Hercules to Draco and will continue to fade. Never visible to the unaided eye, McNaught-Hartley is still at about 10th magnitude and can be viewed by comet seekers using small telescopes.

2000 Telescopic instruments in Earth and space are still tracking a tremendous explosion that occurred across the universe. A nearly unprecedented symphony of international observations began abruptly on March 1 when Earth-orbiting RXTE, Sun-orbiting Ulysses, and asteroid-orbiting NEAR all detected a 10-second burst of high-frequency gamma radiation. Within 48 hours astronomers using the 2.5-meter Nordic Optical Telescope chimed in with the observation of a middle-frequency optical counterpart that was soon confirmed with the 3.5-meter Calar Alto Telescope in Spain. By the next day the explosion was picked up in low-frequency radio waves by the by the European IRAM 30-meter dish in Spain, and then by the VLA telescopes in the US. The Japanese 8-meter Subaru Telescope interrupted a maiden engineering test to trumpet in infrared observations. Major telescopes across the globe soon began playing along as GRB 000301C came into view, detailing unusual behavior. The Hubble Space Telescope captured the above image and was the first to obtain an accurate distance to the explosion, placing it near redshift 2, most of the way across the visible universe. The Keck II Telescope in Hawaii quickly confirmed and refined the redshift. Still, no one is sure what type of explosion this was. The symphony is not over - oddly no host galaxy appears near the position of this explosion. Will one appear as the din of the loud fireball fades?

1999 The Moon almost ruined this photograph. During late March and early April 1997, Comet Hale-Bopp passed nearly in front of the Andromeda Galaxy. Here the Great Comet of 1997 and the Great Galaxy in Andromeda were photographed together on 1997 March 24th. The problem was the brightness of the Moon. The Moon was full that night and so bright that long exposures meant to capture the tails of Hale-Bopp and the disk of M31 would capture instead only moonlight reflected off the Earth's atmosphere. By the time the Moon would set, this opportunity would be gone. That's why this picture was taken during a lunar eclipse.

1998 A progression of beautiful spiral galaxies is illustrated above with three photographs from NASA's Ultraviolet Imaging Telescope (UIT). Flying above the Earth's obscuring layer of atmosphere on the Space Shuttle Columbia during the Astro-1 mission in 1990, UIT's cameras were able to image these distant spirals in the ultraviolet light produced by hot, young stars. These bright stars, newly condensed from gas and dust clouds, give away the location of the spiral arms they are born in. Because they are massive (many times the mass of the Sun), they are shortlived. Dying and fading before they move too far from their birth place they make excellent tracers of spiral structure. From left to right the galaxies are known as M33, M74, and M81 and have progressively more tightly wound spiral arms. Astronomers would classify these as Scd, Sc, and Sb type spirals using a galaxy classification scheme first worked out by Edwin Hubble.

1997 Comet Hale-Bopp is living up to its expectations. Besides the brightness of its coma, a comet is typically remembered by the length of its tails. As visible in the above picture taken last week, Comet Hale-Bopp's blue ion tail shows a dramatic extension, with current reports of about 20 degrees from dark locations. The comet's white dust tail has so far shown a more modest extent but appears to be growing significantly. Comet Hale-Bopp's closest approach to the Sun occurs in about two weeks, and although it will not get much closer to the Sun than does our Earth, Comet Hale-Bopp is likely to tell even more spectacular tails then.

1996 Where did Comet Hyakutake come from? The orbits of the Earth and this brightening comet are shown in the above diagram. The blue disk is bounded by the circular orbit of the Earth about the central Sun. The comet's path outlines the green shape. The shape of the comet's orbit is close to a parabola. The comet has come in from the outer Solar System, will pass near the Earth in late March, and pass near the Sun in late April. Comet Hyakutake will appear bright in late March because it is so close to the Earth, and will again appear bright in late April because it is so close to the Sun. In late March, the comet will be "north" of the Earth and so only visible in the Northern hemisphere. Information about how to see Comet Hyakutake is available from many University astronomy departments and planetaria.

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