Alex Massarsky

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APOD: A Solar Filament Erupts (2014 Jul 20) Image Credit: NASA's GSFC, SDO AIA Team Explanation: What's happened to our Sun? Nothing very unusual -- it just threw a filament. Toward the middle of 2012, a long standing solar filament suddenly erupted into space producing an energetic Coronal Mass Ejection (CME). The filament had been held up for days by the Sun's ever changing magnetic field and the timing of the eruption was unexpected. Watched closely by the Sun-orbiting Solar Dynamics Observatory, the resulting explosion shot electrons and ions into the Solar System, some of which arrived at Earth three days later and impacted Earth's magnetosphere, causing visible aurorae. Loops of plasma surrounding an active region can be seen above the erupting filament in the ultraviolet image. Over the past week the number of sunspots visible on the Sun unexpectedly dropped to zero, causing speculation that the Sun has now passed a very unusual solar maximum, the time in the Sun's 11-year cycle when it is most active. Starship Asterisk* • APOD Discussion Page #APOD

APOD: The Horsehead Nebula from Blue to Infrared (2014 Jul 28) Image Credit & Copyright: Optical: Aldo Mottino & Carlos Colazo, OAC, Córdoba; Infrared: Hubble Legacy Archive 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 is a digital combination of images taken in blue, green, red, and hydrogen-alpha light from the Argentina, and an image taken in infrared light by the orbiting Hubble Space Telescope. Starship Asterisk* • APOD Discussion Page #APOD

APOD: NGC 7023: The Iris Nebula (2014 Aug 02) Image Credit & Copyright: Jimmy Walker Explanation: These clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula, NGC 7023 is not the only nebula in the sky to evoke the imagery of flowers, though. Still, this deep telescopic view shows off the Iris Nebula's range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a hot, young star. The dominant color of the brighter reflection nebula is blue, characteristic of dust grains reflecting starlight. Central filaments of the dusty clouds glow with a faint reddish photoluminesence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs. The pretty blue petals of the Iris Nebula span about six light-years. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Spiral Galaxy NGC 6744 (2014 Aug 08) Image Credit & Copyright: Don Goldman Explanation: Big, beautiful spiral galaxy NGC 6744 is nearly 175,000 light-years across, larger than our own Milky Way. It lies some 30 million light-years distant in the southern constellation Pavo. We see the disk of the nearby island universe tilted towards our line of sight. Orientation and composition give a strong sense of depth to this colorful galaxy portrait that covers an area about the angular size of the full moon. This giant galaxy's yellowish core is dominated by the light from old, cool stars. Beyond the core, spiral arms filled with young blue star clusters and pinkish star forming regions sweep past a smaller satellite galaxy at the lower left, reminiscent of the Milky Way's satellite galaxy the Large Magellanic Cloud. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Rings Around the Ring Nebula (2014 Aug 13) Image Credit: Hubble, Large Binocular Telescope, Subaru Telescope; Composition & Copyright: Robert Gendler Explanation: It is a familiar sight to sky enthusiasts with even a small telescope. There is much more to the Ring Nebula (M57), however, than can be seen through a small telescope. The easily visible central ring is about one light-year across, but this remarkably deep exposure - a collaborative effort combining data from three different large telescopes - explores the looping filaments of glowing gas extending much farther from the nebula's central star. This remarkable composite image includes narrowband hydrogen image, visible light emission, and infrared light emission. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from a dying, sun-like star. The Ring Nebula is about 2,000 light-years away toward the musical constellation Lyra. Starship Asterisk* • APOD Discussion Page #APOD

APOD: No X-rays from SN 2014J (2014 Aug 16) Image Credit: NASA / CXC / SAO / R. Margutti et al. Explanation: Last January, telescopes in observatories around planet Earth were eagerly used to watch the rise of SN 2014J, a bright supernova in nearby galaxy M82. Still, the most important observations may have been from orbit where the Chandra X-ray Observatory saw nothing. Identified as a Type Ia supernova, the explosion of SN2014J was thought to be triggered by the buildup of mass on a white dwarf star steadily accreting material from a companion star. That model predicts X-rays would be generated when the supernova blastwave struck the material left surrounding the white dwarf. But no X-rays were seen from the supernova. The mostly blank close-ups centered on the supernova's position are shown in the before and after inset panels of Chandra's false color X-ray image of the M82 galaxy. The stunning lack of X-rays from SN 2014J will require astronomers to explore other models to explain what triggers these cosmic explosions. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Jupiter and Venus from Earth (2014 Aug 17) Image Credit: Marek Nikodem (PPSAE) Explanation: It was visible around the world. The sunset conjunction of Jupiter and Venus in 2012 was visible almost no matter where you lived on Earth. Anyone on the planet with a clear western horizon at sunset could see them. Pictured above in 2012, a creative photographer traveled away from the town lights of Szubin, Poland to image a near closest approach of the two planets. The bright planets were separated only by three degrees and his daughter striking a humorous pose. A faint red sunset still glowed in the background. Early tomorrow (Monday) morning, the two planets will pass even closer -- only 0.2 degrees apart as visible from some locations -- just before sunrise. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Star Trails Over Indonesia (2014 Aug 18) Image Credit & Licence: HuiChieh (my dark sky) Explanation: Both land and sky were restless. The unsettled land included erupting Mount Semeru in the distance, the caldera of steaming Mount Bromo on the left, flowing fog, and the lights of moving cars along roads that thread between hills and volcanoes in Bromo Tengger Semeru National Park in East Java, Indonesia. The stirring sky included stars circling the South Celestial Pole and a meteor streaking across the image right. The above 270-image composite was taken from King Kong Hill in mid-June over two hours, with a rising Moon lighting the landscape. Starship Asterisk* • APOD Discussion Page #APOD

APOD: In the Center of the Lagoon Nebula (2014 Aug 20) Image Credit: Hubble Legacy Archive, NASA, ESA Processing & Licence: Judy Schmidt Explanation: The center of the Lagoon Nebula is a whirlwind of spectacular star formation. Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long, have been formed by extreme stellar winds and intense energetic starlight. The tremendously bright nearby star, Herschel 36, lights the area. Walls of dust hide and redden other hot young stars. As energy from these stars pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds which may cause the funnels. This picture, spanning about 5 light years, combines images taken by the orbiting Hubble Space Telescope. The Lagoon Nebula, also known as M8, lies about 5,000 light years distant toward the constellation of Sagittarius. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Arp 188 and the Tadpole's Tail (2014 Aug 25) Image Credit: Hubble Legacy Archive, ESA, NASA; Processing & Copyright: Joachim Dietrich Explanation: Why does this galaxy have such a long tail? In this stunning vista, based on image data from the Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from right to left in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper right. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Milky Way over Yellowstone (2014 Aug 27) Image Credit & Copyright: Dave Lane Explanation: The Milky Way was not created by an evaporating lake. The colorful pool of water, about 10 meters across, is known as Silex Spring and is located in Yellowstone National Park in Wyoming, USA. Illuminated artificially, the colors are caused by layers of bacteria that grow in the hot spring. Steam rises off the spring, heated by a magma chamber deep underneath known as the Yellowstone hotspot. Unrelated and far in the distance, the central band of our Milky Way Galaxy arches high overhead, a band lit by billions of stars. The above picture is a 16-image panorama taken late last month. If the Yellowstone hotspot causes another supervolcanic eruption as it did 640,000 years ago, a large part of North America would be affected. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Three Galaxies over New Zealand (2014 Jun 11) Image Credit & Copyright: Mike Mackinven Explanation: No, radio dishes cannot broadcast galaxies. Although they can detect them, the above image features a photogenic superposition during a dark night in New Zealand about two weeks ago. As pictured above, the central part of our Milky Way Galaxy is seen rising to the east on the image left and arching high overhead. Beneath the Galactic arc and just above the horizon are the two brightest satellite galaxies of our Milky Way, with the Small Magellanic Cloud to the left and the Large Magellanic Cloud on the right. The radio dish is the Warkworth Satellite Station located just north of Auckland. Starship Asterisk* • APOD Discussion Page #APOD

APOD: M51: X-Rays from the Whirlpool (2014 Jun 10) Image Credit & Copyright: X-ray: NASA, CXC, R. Kilgard (Wesleyan U.) et al.; Optical: NASA, STScI Explanation: What if we X-rayed an entire spiral galaxy? This was done (again) recently by NASA's Chandra X-ray Observatory for the nearby interacting galaxies known as the Whirlpool (M51). Hundreds of glittering x-ray stars are present in the above Chandra image of the spiral and its neighbor. The image is a conglomerate of X-ray light from Chandra and visible light from the Hubble Space Telescope. The number of luminous x-ray sources, likely neutron star and black hole binary systems within the confines of M51, is unusually high for normal spiral or elliptical galaxies and suggests this cosmic whirlpool has experienced intense bursts of massive star formation. The bright cores of both galaxies, NGC 5194 and NGC 5195 (right and left respectively), also exhibit high-energy activity. In this false-color image where X-rays are depicted in purple, diffuse X-ray emission typically results from multi-million degree gas heated by supernova explosions. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Wolf-Rayet Star 124: Stellar Wind Machine (2014 Jul 01) Image Credit: Hubble Legacy Archive, NASA, ESA Processing & Licence: Judy Schmidt Explanation: Some stars explode in slow motion. Rare, massive Wolf-Rayet stars are so tumultuous and hot that they slowly disintegrating right before our telescopes. Glowing gas globs each typically over 30 times more massive than the Earth are being expelled by violent stellar winds. Wolf-Rayet star WR 124, visible near the above image center spanning six light years across, is thus creating the surrounding nebula known as M1-67. Details of why this star has been slowly blowing itself apart over the past 20,000 years remains a topic of research. WR 124 lies 15,000 light-years away towards the constellation of Sagitta. The fate of any given Wolf-Rayet star likely depends on how massive it is, but many are thought to end their lives with spectacular explosions such as supernovas or gamma-ray bursts. Starship Asterisk* • APOD Discussion Page #APOD

APOD: NGC 4651: The Umbrella Galaxy (2014 Jul 02) Image Credit & Copyright: R. Jay Gabany (Blackbird Observatories) Collaboration: C. Foster (Australian Astronomical Obs.), H. Lux (U. Nottingham, Oxford), A. Romanowsky (San Jose State, UCO), D. Martínez-Delgado (Heidelberg), et al. Explanation: Spiral galaxy NGC 4651 is a mere 62 million light-years distant, toward the well-groomed northern constellation Coma Berenices. About the size of our Milky Way, this island universe is seen to have a faint umbrella-shaped structure that seems to extend (left) some 100 thousand light-years beyond the bright galactic disk. The giant cosmic umbrella is now known to be composed of tidal star streams - extensive trails of stars gravitationally stripped from a smaller satellite galaxy. The small galaxy was eventually torn apart in repeated encounters as it swept back and forth on eccentric orbits through NGC 4651. In fact, the picture insert zooms in on the smaller galaxy's remnant core, identified in an extensive exploration of the system, using data from the large Subaru and Keck telescopes on Mauna Kea. Work begun by a remarkable collaboration of amateur and professional astronomers to image faint structures around bright galaxies suggests that even in nearby galaxies, tidal star streams are common markers of such galactic mergers. The result is explained by models of galaxy formation that also apply to our own Milky Way. Starship Asterisk* • APOD Discussion Page #APOD

APOD: M106 Across the Spectrum (2014 Jul 05) Image Credit: X-ray - NASA / CXC / Caltech / P.Ogle et al., Optical - NASA/STScI, IR - NASA/JPL-Caltech, Radio - NSF/NRAO/VLA Explanation: The spiral arms of bright, active galaxy M106 sprawl through this remarkable multiwavelength portrait, composed of image data from radio to X-rays, across the electromagnetic spectrum. Also known as NGC 4258, M106 can be found toward the northern constellation Canes Venatici. The well-measured distance to M106 is 23.5 million light-years, making this cosmic scene about 60,000 light-years across. Typical in grand spiral galaxies, dark dust lanes, youthful star clusters, and star forming regions trace spiral arms that converge on a bright nucleus. But this composite highlights two anomalous arms in radio (purple) and X-ray (blue) that seem to arise in the central region of M106, evidence of energetic jets of material blasting into the galaxy's disk. The jets are likely powered by matter falling into a massive central black hole. Starship Asterisk* • APOD Discussion Page #APOD

APOD: SN 1006 Supernova Remnant (2014 Jul 12) Image Credit: NASA, ESA, Zolt Levay (STScI) Explanation: A new star, likely the brightest supernova in recorded human history, lit up planet Earth's sky in the year 1006 AD. The expanding debris cloud from the stellar explosion, found in the southerly constellation of Lupus, still puts on a cosmic light show across the electromagnetic spectrum. In fact, this composite view includes X-ray data in blue from the Chandra Observatory, optical data in yellowish hues, and radio image data in red. Now known as the SN 1006 supernova remnant, the debris cloud appears to be about 60 light-years across and is understood to represent the remains of a white dwarf star. Part of a binary star system, the compact white dwarf gradually captured material from its companion star. The buildup in mass finally triggered a thermonuclear explosion that destroyed the dwarf star. Because the distance to the supernova remnant is about 7,000 light-years, that explosion actually happened 7,000 years before the light reached Earth in 1006. Shockwaves in the remnant accelerate particles to extreme energies and are thought to be a source of the mysterious cosmic rays. Starship Asterisk* • APOD Discussion Page #APOD Image Credit: X-ray (blue): NASA/CXC/Rutgers/G.Cassam-Chenaï, J.Hughes et al.; Radio (red): NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell; Optical (orange/yellow): Middlebury College/F.Winkler, NOAO/AURA/NSF/CTIO Schmidt & DSS

APOD: Planetary Nebula NGC 2818 from Hubble (2014 Jul 13) Image Credit: NASA, ESA, Hubble Heritage Team (STScI/AURA) Explanation: NGC 2818 is a beautiful planetary nebula, the gaseous shroud of a dying sun-like star. It could well offer a glimpse of the future that awaits our own Sun after spending another 5 billion years or so steadily using up hydrogen at its core, and then finally helium, as fuel for nuclear fusion. Curiously, NGC 2818 seems to lie within an open star cluster, NGC 2818A, that is some 10,000 light-years distant toward the southern constellation Pyxis (the Compass). At the distance of the star cluster, the nebula would be about 4 light-years across. But accurate velocity measurements show that the nebula's own velocity is very different from the cluster's member stars. The result is strong evidence that NGC 2818 is only by chance found along the line of sight to the star cluster and so may not share the cluster's distance or age. The Hubble image is a composite of exposures through narrow-band filters, presenting emission from nitrogen, hydrogen, and oxygen atoms in the nebula as red, green, and blue hues. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Auroras over Northern Canada (2014 Jul 14) Image Credit & Copyright: Kwon O Chul (TWAN) Explanation: Gusting solar winds and blasts of charged particles from the Sun resulted in several rewarding nights last December for those anticipating auroras. The above image captured dramatic auroras stretching across a sky near the town of Yellowknife in northern Canada. The auroras were so bright that they not only inspired awe, but were easily visible on an image exposure of only 1.3 seconds. A video taken concurrently shows the dancing sky lights evolving in real time as tourists, many there just to see auroras, respond with cheers. The conical dwellings on the image right are teepees, while far in the background, near the image center, is the constellation of Orion. Starship Asterisk* • APOD Discussion Page #APOD

APOD: IC 4603: Reflection Nebula in Ophiuchius (2014 Jul 23) Image Credit & Copyright: Rolf Olsen Explanation: Why does this starfield photograph resemble an impressionistic painting? The effect is created not by digital trickery but by large amounts of interstellar dust. Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, young stars. The dust is dispersed as the star dies and grows as things stick to it in the interstellar medium. Dense dust clouds are opaque to visible light and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. Nebular gas emissions, typically brightest in red light, can combine to form areas seemingly created on an artist's canvas. Photographed above is the central part of the nebula IC 4603 surrounding the bright star SAO 184376 (actually 8th magnitude) which mostly illuminates the blue reflection nebula. IC 4603 can be seen near the very bright star Antares (1st magnitude) toward the constellation of Ophiuchus. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Rho Ophiuchi Wide Field (2014 Jul 27) Image Credit & Copyright: Rogelio Bernal Andreo Explanation: The clouds surrounding the star system Rho Ophiuchi compose one of the closest star forming regions. Rho Ophiuchi itself is a binary star system visible in the light-colored region on the image right. The star system, located only 400 light years away, is distinguished by its colorful surroundings, which include a red emission nebula and numerous light and dark brown dust lanes. Near the upper right of the Rho Ophiuchi molecular cloud system is the yellow star Antares, while a distant but coincidently-superposed globular cluster of stars, M4, is visible between Antares and the red emission nebula. Near the image bottom lies IC 4592, the Blue Horsehead nebula. The blue glow that surrounds the Blue Horsehead's eye -- and other stars around the image -- is a reflection nebula composed of fine dust. On the above image left is a geometrically angled reflection nebula cataloged as Sharpless 1. Here, the bright star near the dust vortex creates the light of surrounding reflection nebula. Although most of these features are visible through a small telescope pointed toward the constellations of Ophiuchus, Scorpius, and Sagittarius, the only way to see the intricate details of the dust swirls, as featured above, is to use a long exposure camera. Starship Asterisk* • APOD Discussion Page #APOD

APOD: M31: The Andromeda Galaxy (2014 Jul 30) Image Credit & Copyright: Jacob Bers (Bersonic) Explanation: Andromeda is the nearest major galaxy to our own Milky Way Galaxy. Our Galaxy is thought to look much like Andromeda. Together these two galaxies dominate the Local Group of galaxies. The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object. Andromeda is frequently referred to as M31 since it is the 31st object on Messier's list of diffuse sky objects. M31 is so distant it takes about two million years for light to reach us from there. Although visible without aid, the above image of M31 was taken with a standard camera through a small telescope. Much about M31 remains unknown, including how it acquired its unusual double-peaked center. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Veins of Heaven (2014 Jul 31) Image Credit & Copyright: P-M Hedén (Clear Skies, TWAN) Explanation: Transfusing sunlight through a a still dark sky, this exceptional display of noctilucent clouds was captured earlier this month above the island of Gotland, Sweden. From the edge of space, about 80 kilometers above Earth's surface, the icy clouds reflect sunlight even though the Sun itself is below the horizon as seen from the ground. Usually spotted at high latitudes in summer months the night shining clouds made a strong showing this July. Also known as polar mesospheric clouds they are understood to form as water vapor driven into the cold upper atmosphere condenses on the fine dust particles supplied by disintegrating meteors or volcanic ash. NASA's AIM mission provides daily projections of noctilucent clouds as seen from space. Starship Asterisk* • APOD Discussion Page #APOD #TWAN

APOD: At the Edge of NGC 2174 (2014 Apr 03) Image Credit: NASA, ESA, Hubble Heritage Team (STScI/AURA) Explanation: This fantastic skyscape lies near the edge of NGC 2174 a star forming region about 6,400 light-years away in the nebula-rich constellation of Orion. It follows mountainous clouds of gas and dust carved by winds and radiation from the region's newborn stars, now found scattered in open star clusters embedded around the center of NGC 2174, off the top of the frame. Though star formation continues within these dusty cosmic clouds they will likely be dispersed by the energetic newborn stars within a few million years. Recorded at infrared wavelengths by the Hubble Space Telescope, the interstellar scene spans about 6 light-years. The image celebrates the upcoming 24th anniversary of Hubble's launch onboard the space shuttle orbiter Discovery on April 24, 1990. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Along the Western Veil (2014 Apr 04) Image Processing: Oliver Czernetz Data: Digitized Sky Survey (POSS-II) Explanation: Delicate in appearance, these filaments of shocked, glowing gas, draped in planet Earth's sky toward the constellation of Cygnus, make up the western part of the Veil Nebula. The Veil Nebula itself is a large supernova remnant, an expanding cloud born of the death explosion of a massive star. Light from the original supernova explosion likely reached Earth over 5,000 years ago. Blasted out in the cataclysmic event, the interstellar shock wave plows through space sweeping up and exciting interstellar material. The glowing filaments are really more like long ripples in a sheet seen almost edge on, remarkably well separated into atomic hydrogen (red) and oxygen (blue-green) gas. Also known as the Cygnus Loop, the Veil Nebula now spans nearly 3 degrees or about 6 times the diameter of the full Moon. While that translates to over 70 light-years at its estimated distance of 1,500 light-years, this wide image of the western portion spans about half that distance. Brighter parts of the western Veil are recognized as separate nebulae, including The Witch's Broom (NGC 6960) along the top of this view and Pickering's Triangle (NGC 6979) below and right of center. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Fresh Tiger Stripes on Saturn's Enceladus (2014 Apr 06) Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA Explanation: Do underground oceans vent through the tiger stripes on Saturn's moon Enceladus? Long features dubbed tiger stripes are known to be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Evidence for this has come from the robot Cassini spacecraft now orbiting Saturn. Pictured above, a high resolution image of Enceladus is shown from a close flyby. The unusual surface features dubbed tiger stripes are visible in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead. Most recently, an analysis of slight gravity deviations has given an independent indication of underground oceans. Such research is particularly interesting since such oceans would be candidates to contain life. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Two Rings for Asteroid Chariklo (2014 Apr 09) Video Illustration Credit: Lucie Maquet, Observatoire de Paris, LESIA Explanation: Asteroids can have rings. In a surprising discovery announced two weeks ago, the distant asteroid 10199 Chariklo was found to have at least two orbiting rings. Chariklo's diameter of about 250 kilometers makes it the largest of the measured centaur asteroids, but now the smallest known object to have rings. The centaur-class minor planet orbits the Sun between Saturn and Uranus. The above video gives an artist's illustration of how the rings were discovered. As Chariklo passed in 2013 in front of a faint star, unexpected but symmetric dips in the brightness of the star revealed the rings. Planetary astronomers are now running computer simulations designed to investigate how Chariklo's unexpected ring system might have formed, how it survives, and given the asteroid's low mass and close passes of other small asteroids and the planet Uranus, how long it may last. Starship Asterisk* • APOD Discussion Page #APOD

APOD: M42: Inside the Orion Nebula (2014 Apr 08) Image Credit: R. Villaverde, Hubble Legacy Archive, NASA Explanation: The Great Nebula in Orion, an immense, nearby starbirth region, is probably the most famous of all astronomical nebulas. Here, glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1500 light-years away. In the above deep image composite in assigned colors taken by the Hubble Space Telescope wisps and sheets of dust and gas are particularly evident. The Great Nebula in Orion can be found with the unaided eye near the easily identifiable belt of three stars in the popular constellation Orion. In addition to housing a bright open cluster of stars known as the Trapezium, the Orion Nebula contains many stellar nurseries. These nurseries contain much hydrogen gas, hot young stars, proplyds, and stellar jets spewing material at high speeds. Also known as M42, the Orion Nebula spans about 40 light years and is located in the same spiral arm of our Galaxy as the Sun. Starship Asterisk* • APOD Discussion Page #APOD

APOD: Clouds and Crosses over Haleakala (2014 Apr 12) Image Credit & Copyright: Wally Pacholka (TWAN) Explanation: Aloha and welcome to a breathtaking skyscape. The dreamlike panoramic view from March 27 looks out over the 10,000 foot summit of Haleakala on Maui, Hawai'i. A cloud layer seeps over the volcanic caldera's edge with the Milky Way and starry night sky above. Head of the Northern Cross asterism, supergiant star Deneb lurks within the Milky Way's dust clouds and nebulae at the left. From there you can follow the arc of the Milky Way all the way to the stars of the more compact Southern Cross, just above the horizon at the far right. A yellowish Mars is right of center, near the top of the frame, with rival red giant Antares below it, closer to the Milky Way's central bulge. Need some help identifying the stars? Just slide your cursor over the picture, or download this labeled panorama. Starship Asterisk* • APOD Discussion Page #APOD