George Cobb

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APOD: Molecular Cloud Barnard 68 (2012 Jan 29) Image Credit: FORS Team, 8.2-meter VLT Antu, ESO Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light. Starship Asterisk* • APOD Discussion Page

APOD: Blue Marble Earth from Suomi NPP (2012 Jan 30) Image Credit: NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring Explanation: Behold one of the more detailed images of the Earth yet created. This Blue Marble Earth montage shown above -- created from photographs taken by the Visible/Infrared Imager Radiometer Suite (VIIRS) instrument on board the new Suomi NPP satellite -- shows many stunning details of our home planet. The Suomi NPP satellite was launched last October and renamed last week after Verner Suomi, commonly deemed the father of satellite meteorology. The composite was created from the data collected during four orbits of the robotic satellite taken earlier this month and digitally projected onto the globe. Many features of North America and the Western Hemisphere are particularly visible on a high resolution version of the image. Previously, several other Blue Marble Earth images have been created, some at even higher resolution. Starship Asterisk* • APOD Discussion Page

APOD: The Helix Nebula from the VISTA Telescope (2012 Jan 31) Credit: ESO/VISTA/J. Emerson; Acknowledgment: Cambridge Astronomical Survey Unit Explanation: Will our Sun look like this one day? The Helix Nebula is one of brightest and closest examples of a planetary nebula, a gas cloud created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix. The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce. The Helix Nebula, given a technical designation of NGC 7293, lies about 700 light-years away towards the constellation of the Water Bearer (Aquarius) and spans about 2.5 light-years. The above picture was taken three colors on infrared light by the 4.1-meter Visible and Infrared Survey Telescope for Astronomy (VISTA) at the European Southern Observatory's Paranal Observatory in Chile. A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin. Starship Asterisk* • APOD Discussion Page

APOD: Flowing Barchan Sand Dunes on Mars (2012 Apr 22) Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA Explanation: When does Mars act like a liquid? Although liquids freeze and evaporate quickly into the thin atmosphere of Mars, persistent winds may make large sand dunes appear to flow and even drip like a liquid. Visible on the above image right are two flat top mesas in southern Mars when the season was changing from Spring to Summer. A light dome topped hill is also visible on the far left of the image. As winds blow from right to left, flowing sand on and around the hills leaves picturesque streaks. The dark arc-shaped droplets of fine sand are called barchans, and are the interplanetary cousins of similar Earth-based sand forms. Barchans can move intact a downwind and can even appear to pass through each other. When seasons change, winds on Mars can kick up dust and are monitored to see if they escalate into another of Mars' famous planet-scale sand storms. Starship Asterisk* • APOD Discussion Page

APOD: M51: The Whirlpool Galaxy (2012 June 02) Image Credit & Copyright: Marco Burali, Tiziano Capecchi, Marco Mancini (Osservatorio MTM) Explanation: Follow the handle of the Big Dipper away from the dipper's bowl until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (top), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the human eye, deep images like this one can reveal the faint tidal debris around the smaller galaxy. Starship Asterisk* • APOD Discussion Page

APOD: Northern Green Flash (2012 June 23) Image Credit & Copyright: Göran Strand Explanation: As seen from Frösön island in northern Sweden the Sun did set a day after the summer solstice. From that location below the arctic circle it settled slowly behind the northern horizon. During the sunset's final minute, this remarkable sequence of 7 images follows the distorted edge of the solar disk as it just disappears against a distant tree line, capturing both a green and blue flash. Not a myth even in a land of runes, the colorful but ellusive glints are caused by atmospheric refraction enhanced by long, low, sight lines and strong atmospheric temperature gradients. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: The Eagle Rises (2012 July 21) Image Credit: Apollo 11, NASA Stereo Image Copyright: John Kaufmann (ALSJ) Explanation: Get out your red/blue glasses and check out this remarkable stereo view from lunar orbit. Created from two photographs (AS11-44-6633, AS11-44-6634) taken by astronaut Michael Collins during the 1969 Apollo 11 mission, the 3D anaglyph 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 near side. Poised beyond the lunar horizon, is our fair planet Earth. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: The Milky Way Over Monument Valley (2012 Aug 01) Image Credit & Copyright: Wally Pacholka (, TWAN) Explanation: You don't have to be at Monument Valley to see the Milky Way arch across the sky like this -- but it helps. Only at Monument Valley USA would you see a picturesque foreground that includes these iconic rock peaks called buttes. Buttes are composed of hard rock left behind after water has eroded away the surrounding soft rock. In the above image taken about two months ago, the closest butte on the left and the butte to its right are known as the Mittens, while Merrick Butte can be seen just further to the right. High overhead stretches a band of diffuse light that is the central disk of our spiral Milky Way Galaxy. The band of the Milky Way can be spotted by almost anyone on almost any clear night when far enough from a city and surrounding bright lights. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: South Pole Star Trails (2012 Aug 02) Image Credit & Copyright: Robert Schwarz (South Pole Station) Explanation: No star dips below the horizon and the Sun never climbs above it in this remarkable Lewin's Challenge image of 24 hour long star trails. Showing all the trails as complete circles, such an image could be achieved only from two places on planet Earth. This example was recorded during the course of May 1, 2012, the camera in a heated box on the roof of MAPO, the Martin A. Pomerantz Observatory at the South Pole. Directly overhead in the faint constellation Octans is the projection of Earth's rotational axis, the South Celestial Pole, at the center of all the star trail circles. Not so well placed as Polaris and the North Celestial Pole, the star leaving the small but still relatively bright circle around the South Celestial Pole is Beta Hydri. A shimmering apparition of the aurora australis also visited on this 24 hour night. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: The Cat's Eye Nebula (2012 Aug 26) Image Credit: J. P. Harrington (U. Maryland) & K. J. Borkowski (NCSU) HST, NASA Explanation: Three thousand light-years away, a dying star throws off shells of glowing gas. This image from the Hubble Space Telescope reveals the Cat's Eye Nebula to be one of the most complex planetary nebulae known. In fact, the features seen in the Cat's Eye are so complex that astronomers suspect the bright central object may actually be a binary star system. The term planetary nebula, used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, high resolution images reveal them to be stars surrounded by cocoons of gas blown off in the late stages of stellar evolution. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: M45: The Pleiades Star Cluster (2012 Sep 03) Image Credit & Copyright: Robert Gendler Explanation: Perhaps the most famous star cluster on the sky, the Pleiades can be seen without binoculars from even the depths of a light-polluted city. Also known as the Seven Sisters and M45, the Pleiades is one of the brightest and closest open clusters. The Pleiades contains over 3000 stars, is about 400 light years away, and only 13 light years across. Quite evident in the above photograph are the blue reflection nebulae that surround the brighter cluster stars. Low mass, faint, brown dwarfs have also been found in the Pleiades. (Editors' note: The prominent diffraction spikes are caused by the telescope itself and may be either distracting or provide aesthetic enhancement, depending on your point of view.) Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: A Space Shuttle Over Los Angeles (2012 Sep 26) Image Credit & Copyright: Stephen Confer Explanation: It's not every day that a space shuttle lands at LAX. Although this was a first for the major Los Angeles airport hub, it was a last for the space shuttle Endeavour, as it completed its tour of California skies and landed, albeit atop a 747, for the last time. During its last flight the iconic shuttle and its chase planes were photographed near several of California's own icons including the Golden Gate Bridge in San Francisco, the Hollywood Sign, and the skyline of Los Angeles. Previously, in May, the space shuttle Enterprise was captured passing behind several of New York City's icons on its way to the Intrepid Sea, Air, & Space Museum. Pictured above, the piggybacking shuttle was snapped on approach last week to LAX as it crossed above and beyond a major Los Angeles street. Now retired, the space shuttles are all museum pieces, with the above shuttle scheduled to be towed along the streets of LA to the California Science Center. A Space Shuttle Endeavour Retrospective Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Aurora and Fireball Over Norway (2012 Oct 05) Image Credit & Copyright: Ole C. Salomonsen (Arctic Light Photo) Explanation: What's happening behind that mountain? A convergence of variable sky spectacles. One night in mid-September near Tromsø, Norway, high red aurora could be seen shimmering through lower green aurora in a way that created a striking and somewhat unusual violet glow. Suddenly, though, the sky flashed with the brightest fireball the astrophotographer had ever seen, as a small pebble from outer space violently crashed into the Earth's atmosphere. The glow illuminated the distant mountain peak known as Otertinden of the Lyngen Alps. The bright meteor, which coincidently disappeared behind the same mountain, was also reflected in the foreground Signalelva River. Although you might consider yourself lucky to see either an aurora or a bright meteor, pictures of them together have been recorded several times previously. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Nauset Light Star Trails (2012 Oct 10) Image Credit & Copyright: Chris Cook Explanation: In myth, Atlas holds up the heavens, but in this scene they seem to pivot around a lighthouse beacon. Photographed with a camera fixed to a tripod, the well-planned 30 minute exposure records star trails in the northern sky, reflecting the daily rotation of planet Earth. Hidden behind the top of the prominent Nauset Lighthouse on Cape Cod, Massachusetts, USA, the North Celestial Pole is at the center of all the star trail arcs. Making a complete circle, 360 degrees, in 24 hours, the star trail arcs cover 15 degrees each hour or 7.5 degrees in thirty minutes. Foreground lighting is courtesy of September 23rd's first quarter moonlight. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: The Horsehead Nebula (2012 Oct 21) Credit & Copyright: Nigel Sharp (NOAO), KPNO, AURA, NSF Explanation: One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1,500 years to reach us from the Horsehead Nebula. The above image was taken with the 0.9-meter telescope at Kitt Peak National Observatory. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: NGC 206 and the Star Clouds of Andromeda (2012 Oct 24) Image Credit & Copyright: Bob and Janice Fera (Fera Photography) Explanation: The large stellar association cataloged as NGC 206 is nestled within the dusty arms of neighboring spiral galaxy Andromeda (M31), 2.5 million light-years distant. Seen near the center of this gorgeous close-up of the southwestern extent of Andromeda's disk, the bright, blue stars of NGC 206 indicate its youth. Its youngest massive stars are less than 10 million years old. Much larger than the clusters of young stars in the disk of our Milky Way galaxy known as open or galactic clusters, NGC 206 spans about 4,000 light-years. That's comparable in size to the giant stellar nurseries NGC 604 in nearby spiral M33 and the Tarantula Nebula, in the Large Magellanic Cloud. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

Get ready for a total solar eclipse! ESA Space Science IOTW | 2012 Nov 12 Tomorrow’s total solar eclipse will only be visible in its entirety to ground-based observers watching from northern Australia, but ESA’s Sun-watching Proba-2 satellite will have a ringside seat from its orbit around Earth. During a total solar eclipse the Moon moves in front of the Sun as seen from Earth, their separation and alignment such that the Moon appears large enough to temporarily block out the Sun’s light. An eerie light is cast over ground observers as the imposing black disc of the Moon briefly replaces the Sun’s bright face. Totality – when the Sun is completely obscured – occurs tomorrow at 22:11:48 GMT over the South Pacific for four minutes and two seconds. Observers along the east coast of Queensland, Australia, will be the lucky few to see the total eclipse, enjoying totality for about two minutes as the Sun rises 14 degrees above the horizon. During totality the Sun appears to have a white halo – a rare glimpse of the Sun’s million-degree plasma atmosphere, or corona, which is too washed out by the Sun’s brightness to be observed normally. In the image presented here, a Proba-2 image of the solar disc taken during the total eclipse of July 2010 is combined with ground-based images taken at the same time to reveal the exquisite details of the solar corona. ... Image Credits: ESA/Proba-2 consortium/SWAP team/Institut d’Astrophysique de Paris (CNRS & UPMC), S. Koutchmy/J. Mouette Copyright: Jean Mouette

APOD: NGC 6357's Cathedral to Massive Stars (2012 Nov 18) Image Credit: NASA, ESA and J. M. Apellániz (IAA, Spain) Explanation: How massive can a normal star be? Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, nearly making it the record holder. This star is the brightest object located just above the gas front in the above image. Close inspection of images taken with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least. Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record. Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357. Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be breaking out and illuminating a spectacular cocoon. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Plasma Jets from Radio Galaxy Hercules A (2012 Dec 05) Image Credit: NASA, ESA, S. Baum & C. O'Dea (RIT), R. Perley & W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA) Explanation: Why does this galaxy emit such spectacular jets? No one is sure, but it is likely related to an active supermassive black hole at its center. The galaxy at the image center, Hercules A, appears to be a relatively normal elliptical galaxy in visible light. When imaged in radio waves, however, tremendous plasma jets over one million light years long appear. Detailed analyses indicate that the central galaxy, also known as 3C 348, is actually over 1,000 times more massive than our Milky Way Galaxy, and the central black hole is nearly 1,000 times more massive than the black hole at our Milky Way's center. Pictured above is a visible light image obtained by the Earth-orbiting Hubble Space Telescope superposed with a radio image taken by the recently upgraded Very Large Array (VLA) of radio telescopes in New Mexico, USA. The physics that creates the jets remains a topic of research with a likely energy source being infalling matter swirling toward the central black hole. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Earth at Night (2012 Dec 07) Image Credit : NASA, NOAA NGDC, Suomi-NPP, Earth Observatory, Data and Processing: Chris Elvidge and Robert Simmon Explanation: This remarkably complete view of Earth at night is a composite of cloud-free, nighttime images. The images were collected during April and October 2012 by the Suomi-NPP satellite from polar orbit about 824 kilometers (512 miles) above the surface using its Visible Infrared Imaging Radiometer Suite (VIIRS). VIIRS offers greatly improved resolution and sensitivity compared to past global nightlight detecting instrumentation on DMSP satellites. It also has advantages compared to cameras on the International Space Station, passing over the same point on Earth every two or three days while Suomi-NPP passes over the same point twice a day at about 1:30am and 1:30pm local time. Easy to recognize here, city lights identify major population centers, tracking the effects of human activity and influence across the globe. That makes nighttime images of our fair planet among the most interesting and important views from space. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: A Sun Pillar Over Sweden (2012 Dec 18) Image Credit & Copyright: Göran Strand Explanation: Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light. Ice sometimes forms flat, six-sided shaped crystals as it falls from high-level clouds. Air resistance causes these crystals to lie nearly flat much of the time as they flutter to the ground. Sunlight reflects off crystals that are properly aligned, creating the sun-pillar effect. In the above picture taken last week, a sun-pillar reflects light from a Sun setting over Östersund, Sweden. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Orion over El Castillo (2012 Dec 21) Image Credit & Copyright: Stéphane Guisard (Los Cielos de America, TWAN) Credits: D. Flores and B. Pichardo (IA-UNAM), P. Sánchez and R. Nafate (INAH) Explanation: Welcome to the December solstice, a day the world does not end ... even according to the Mayan Calendar. To celebrate, consider this dramatic picture of Orion rising over El Castillo, the central pyramid at Chichén Itzá, one of the great Mayan centers on the Yucatán peninsula. Also known as the Temple of Kukulkan it stands 30 meters tall and 55 meters wide at the base. Built up as a series of square terraces by the pre-Columbian civilization between the 9th and 12th century, the structure can be used as a calendar and is noted for astronomical alignments. In fact, the Mayans were accomplished astronomers and mathematicians, accurately using the cyclic motions of the stars, Sun, Moon, and planets to measure time and construct calendars. Peering through clouds in this night skyscape, stars in the modern constellation Orion the Hunter represented a turtle in the Mayan sky. Tak sáamal. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Hyades for the Holidays (2012 Dec 24) Image Credit & Copyright: Jerry Lodriguss (Catching the Light) Explanation: Recognized since antiquity and depicted on the shield of Achilles according to Homer, stars of the Hyades cluster form the head of the constellation Taurus the Bull. Their general V-shape is anchored by Aldebaran, the eye of the Bull and by far the constellation's brightest star. Yellowish in appearance, red giant Aldebaran is not a Hyades cluster member, though. Modern astronomy puts the Hyades cluster 151 light-years away making it the nearest established open star cluster, while Aldebaran lies at less than half that distance, along the same line-of-sight. Along with colorful Hyades stars, this stellar holiday portrait locates Aldebaran just below center, as well as another open star cluster in Taurus, NGC 1647 at the left, some 2,000 light-years or more in the background. Just slide your cursor over the image to identify the stars. The central Hyades stars are spread out over about 15 light-years. Formed some 800 million years ago, the Hyades star cluster may share a common origin with M44 (Praesepe), a naked-eye open star cluster in Cancer, based on M44's motion through space and remarkably similar age. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Doomed Star Eta Carinae (2012 Dec 30) Image Credit: J. Morse (Arizona State U.), K. Davidson (U. Minnesota) et al., WFPC2, HST, NASA Explanation: Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This image, taken in 1996, brought out new details in the unusual nebula that surrounds this rogue star. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: The Einstein Cross Gravitational Lens (2013 Jan 02) Image Credit & Copyright: J. Rhoads (Arizona State U.) et al., WIYN, AURA, NOAO, NSF Explanation: Most galaxies have a single nucleus -- does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar. The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross. Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Open Star Clusters M35 and NGC 2158 (2013 Jan 03) Image Credit & Copyright: Dieter Willasch (Astro-Cabinet) Explanation: Open clusters of stars can be near or far, young or old, and diffuse or compact. Found near the plane of our Milky Way galaxy, they contain from 100 to 10,000 stars, all of which formed at nearly the same time. Bright blue stars frequently distinguish younger open clusters. M35, on the upper left, is relatively nearby at 2800 light years distant, relatively young at 150 million years old, and relatively diffuse, with about 2500 stars spread out over a volume 30 light years across. An older and more compact open cluster, NGC 2158, is at the lower right. NGC 2158 is four times more distant than M35, over 10 times older, and much more compact with many more stars in roughly the same volume of space. NGC 2158's bright blue stars have self-destructed, leaving cluster light to be dominated by older and yellower stars. Both clusters are seen toward the constellation of Gemini. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: Sunrise at Tycho (2013 Jan 04) Credit: NASA/GSFC/Arizona State Univ/Lunar Reconnaissance Orbiter Explanation: Tycho crater's central peak complex casts a long, dark shadow near local sunrise in this spectacular lunarscape. The dramatic oblique view was recorded on June 10, 2011 by the Lunar Reconnaissance Orbiter. Shown in amazing detail, boulder strewn slopes and jagged shadows appear in the highest resolution version at 1.5 meters per pixel. The rugged complex is about 15 kilometers wide, formed in uplift by the giant impact that created the well-known ray crater 100 million years ago. The summit of its central peak reaches 2 kilometers above the Tycho crater floor.!.html Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: AE Aurigae and the Flaming Star Nebula (2013 Jan 07) Image Credit & Copyright: Martin Pugh Explanation: AE Aurigae is called the flaming star. The surrounding nebula IC 405 is named the Flaming Star Nebula and the region seems to harbor smoke, but there is no fire. Fire, typically defined as the rapid molecular acquisition of oxygen, happens only when sufficient oxygen is present and is not important in such high-energy, low-oxygen environments. The material that appears as smoke is mostly interstellar hydrogen, but does contain smoke-like dark filaments of carbon-rich dust grains. The bright star AE Aurigae, visible near the nebula center, is so hot it is blue, emitting light so energetic it knocks electrons away from atoms in the surrounding gas. When an atom recaptures an electron, light is emitted creating the surrounding emission nebula. In this cosmic portrait, the Flaming Star nebula lies about 1,500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga). Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: NGC 602 and Beyond (2013 Jan 13) Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) - ESA/Hubble Collaboration Explanation: Near the outskirts of the Small Magellanic Cloud, a satellite galaxy some 200 thousand light-years distant, lies 5 million year young star cluster NGC 602. Surrounded by natal gas and dust, NGC 602 is featured in this stunning Hubble image of the region. Fantastic ridges and swept back shapes strongly suggest that energetic radiation and shock waves from NGC 602's massive young stars have eroded the dusty material and triggered a progression of star formation moving away from the cluster's center. At the estimated distance of the Small Magellanic Cloud, the picture spans about 200 light-years, but a tantalizing assortment of background galaxies are also visible in the sharp Hubble view. The background galaxies are hundreds of millions of light-years or more beyond NGC 602. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD

APOD: NGC 1309: Spiral Galaxy and Friends (2013 Jan 16) Image Credit: Hubble Legacy Archive, ESA, NASA; Processing - Martin Pugh Explanation: A gorgeous spiral galaxy some 100 million light-years distant, NGC 1309 lies on the banks of the constellation of the River (Eridanus). NGC 1309 spans about 30,000 light-years, making it about one third the size of our larger Milky Way galaxy. Bluish clusters of young stars and dust lanes are seen to trace out NGC 1309's spiral arms as they wind around an older yellowish star population at its core. Not just another pretty face-on spiral galaxy, observations of NGC 1309's recent supernova and Cepheid variable stars contribute to the calibration of the expansion of the Universe. Still, after you get over this beautiful galaxy's grand design, check out the array of more distant background galaxies also recorded in the above, sharp, reprocessed, Hubble Space Telescope view. Starship Asterisk* • APOD Discussion Page Starship Asterisk* • On This Day in APOD