APOD Retrospective: March 10

A nostalgic look back at Astronomy Picture of the Day
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APOD Retrospective: March 10

Post by bystander » Sun Mar 11, 2012 12:14 am

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2015 Several key conditions came together to create this award-winning shot. These included a dark night, few clouds, an epic auroral display, and a body of water that was both calm enough and unfrozen enough to show reflected stars. The featured skyscape of activity and serenity appeared over Iceland's Vatnajökull Glacier a year ago January, with the Jökulsárlón Iceberg Lagoon captured in the foreground. Aurora filled skies continue to be common near Earth's poles as our Sun, near Solar Maximum, continues to expel energetic clouds of plasma into the Solar System.

2014 What is creating the gamma rays at the center of our Galaxy? Excitement is building that one answer is elusive dark matter. Over the past few years the orbiting Fermi Gamma-ray Space Telescope has been imaging our Galaxy's center in gamma-rays. Repeated detailed analyses indicate that the region surrounding the Galactic center seems too bright to be accounted by known gamma-ray sources. A raw image of the Galactic Center region in gamma-rays is shown above on the left, while the image on the right has all known sources subtracted -- leaving an unexpected excess. An exciting hypothetical model that seems to fit the excess involves a type of dark matter known as WIMPs, which may be colliding with themselves to create the detected gamma-rays. This hypothesis is controversial, however, and debate and more detailed investigations are ongoing. Finding the nature of dark matter is one of the great quests of modern science, as previously this unusual type of cosmologically pervasive matter has shown itself only through gravitation.

2013 Aloha and welcome to a breathtaking skyscape. The dreamlike panoramic view looks out from the 4,200 meter volcanic summit of Mauna Kea, Hawai'i, across a layer of clouds toward a starry night sky and the rising Milky Way. Anchoring the scene on the far left is the dome of the Canada-France-Hawaii Telescope (CFHT), with north star Polaris shining beyond the dome to the right. Farther right, headed by bright star Deneb, the Northern Cross asterism is embedded along the plane of the Milky Way as it peeks above the horizon. Both Northern Cross and brilliant white Vega hang over a foreground grouping of cinder cones. Near the center are the reddish nebulae, stars and dust clouds of the central Milky Way. Below, illumination from the city lights of Hilo creates an eerie, greenish glow in the clouds. Red supergiant star Antares shines above the Milky Way's central bulge while bright Alpha Centauri lies still farther right, along the dusty galactic plane. Finally, at the far right is the large Gemini North Observatory. The compact group of stars known as the Southern Cross is just left of the telescope dome. Need some help identifying the stars? Just slide your cursor over the picture, or download this smaller, labeled panorama.

2012 As viewed from a well chosen location at sunset, the gorgeous Full Moon rose behind Mount Hamilton, east of San Jose, California on March 7. The lunar disk frames historic Lick Observatory perched on the mountain's 4,200 foot summit. Both observatory and Moon echo the warm color of sunlight (moonlight is reflected sunlight) filtered by a long path through the atmosphere. Substantial atmospheric refraction contributes the Moon's ragged, green rim. Of course, the March Full Moon is also known as the Full Worm Moon. In the telescopic photo, Lick's 40 inch Nickel Telescope dome is on the left. The large dome on the right houses Lick's Great 36 inch Refractor.

2011 As evening twilight faded on March 7, sky gazers around planet Earth enjoyed a beautiful pairing of young crescent Moon and brilliant planet Jupiter. Along with stars setting in the west, the two bright celestial beacons, Moon above and Jupiter below, leave short trails in this well-planned time exposure, a composite of 54 individual frames each 4 seconds long. On its final flight, the Space Shuttle Discovery and International Space Station form the second close pairing in the night skyscape. Still glinting in the sunlight in low Earth orbit, they gracefully trace overlapping arcs from lower right to upper left. Moon, Jupiter, Discovery, and ISS are reflected in the calm waters of Lake Bakonybél, Hungary. Want to see the sequence of frames as a short youtube video? Check it out here. In the video, the trails of the ISS and Discovery are seen to separate as the pair passes above the Moon.

2010 What's happening on the surface of Saturn's moon Helene? The moon was imaged in unprecedented detail last week as the robotic Cassini spacecraft orbiting Saturn swooped to within two Earth diameters of the diminutive moon. Although conventional craters and hills appear, the above raw and unprocessed image also shows terrain that appears unusually smooth and streaked. Planetary astronomers will be inspecting these detailed images of Helene to glean clues about the origin and evolution of the 30-km across floating iceberg. Helene is also unusual because it circles Saturn just ahead of the large moon Dione, making it one of only four known Saturnian moons to occupy a gravitational well known as a stable Lagrange point.

2009 Adrift 1,500 light-years away in one of the night sky's most recognizable constellations, the glowing Orion Nebula and the dark Horsehead Nebula are contrasting cosmic vistas. They appear in opposite corners of this stunning mosaic taken with a digital camera attached to a small telescope. The magnificent emission region, the Orion Nebula (aka M42), lies at the upper right of the picture. Immediately to its left is a prominent bluish reflection nebula sometimes called the Running Man. The Horsehead nebula appears as a dark cloud, a small silhouette notched against the long red glow at the lower left. Alnitak is the easternmost star in Orion's belt and is seen as the brightest star to the left of the Horsehead. Below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes. Pervasive tendrils of glowing hydrogen gas are easily traced throughout the region in this deep field image of the same region.

2008 Last week, Mercury, Venus, and the Moon all appeared close together in Earth's sky. This picturesque conjunction was caught on camera behind elements of the Australia Telescope Compact Array (ATCA) near the town of Narrabri in rural New South Wales. The ATCA consists of six radio telescopes in total, each one larger than a house. Together they form one of the highest resolution measurement devices in the world. Impressive planetary conjunctions occur every few years. Involving the brightest objects in the night sky, this alignment was easy to spot just before sunrise. In the picture, taken on the morning of March 6, Mercury is the highest of the three bright celestial beacons.

2007 A red Moon rose over Cape Cod, Massachusetts, USA on March 3rd, immersed in Earth's shadow near the total phase of a lunar eclipse. This serene portrait of the eclipsed Moon in a dark blue twilight sky also features the Highland Lighthouse (aka Cape Cod lighthouse), another more locally familiar beacon in the night. Now automated, the 66 foot tall structure in use today was built in 1857. How often has there been an eclipse within view of the Highland light? For locations on planet Earth there are about two eclipse seasons each year. So, eclipses have actually had many chances to be part of the pictorial history of the Highland Lighthouse, including a total solar eclipse in 1932.

2006 Based on data from Cassini spacecraft instruments, researchers are now arguing that liquid water reservoirs exist only tens of meters below the surface of Saturn's small (500 kilometer diameter) but active moon Enceladus. The exciting new results center around towering jets and plumes of material erupting from the moon's surface. The plumes originate in the long tiger stripe fractures of the south polar region pictured here. Detailed models suport conclusions that the plumes arise from near-surface pockets of liquid water at temperatures of 273 kelvins (0 degrees Celsius), even though Enceladus has a surface temperature of about 73 kelvins (-200 degrees Celsius). Clearly an important step in the search for water and the potential for the origin of life beyond planet Earth, such near-surface reservoirs of water would be far more accessible than, for example, the internal ocean detected on the Jovian moon Europa.

2005 Drifting through the Orion Arm of the spiral Milky Way Galaxy, this cosmic cloud by chance echoes the outline of California on the west coast of the United States. Our own Sun also lies within the Milky Way's Orion Arm, only about 1,500 light-years from the California Nebula. Also known as NGC 1499, the classic emission nebula is around 100 light-years long. It glows with the red light characteristic of hydrogen atoms recombining with long lost electrons, stripped away (ionized) by energetic starlight. In this case, the star most likely providing the energetic starlight is the bright, hot, bluish Xi Persei, just right of the nebula and above picture center. Fittingly, this composite picture was made with images from a telescope in California - the 48-inch (1.2-meter) Samuel Oschin Telescope - taken as a part of the second National Geographic Palomar Observatory Sky Survey.

2004 How prevalent was water on Mars? Results from the Spirit rover now indicate that Gusev crater likely had a wet past, a result that comes shortly after Spirit's twin rover Opportunity uncovered clear evidence of past water at Meridiani Planum on the other side of Mars. Evidence uncovered by Spirit and released last week focussed on a large rock of unusual shape nicknamed Humphrey, shown above near the image bottom. Detailed inspection of the rock revealed a bright material filling internal cracks. Such material may have crystallized from water trickling through the volcanic rock. The amount of Mars once covered by ancient water remains unknown, as both rovers landed in regions thought likely to once be underwater. Spirit continues to roll across Mars, recently passing the 300-meter mark on its way to Bonneville crater.

2003 Why do many galaxies appear as spirals? A striking example is M101, shown above, whose relatively close distance of about 22 million light years allow it to be studied in some detail. Recent evidence indicates that a close gravitational interaction with a neighboring galaxy created waves of high mass and condensed gas which continue to orbit the galaxy center. These waves compress existing gas and cause star formation. One result is that M101, also called the Pinwheel Galaxy, has several extremely bright star-forming regions (called HII regions) spread across its spiral arms. M101 is so large that its immense gravity distorts smaller nearby galaxies.

2002 On 1996 March 22, a Galaxy and a comet shared the southern sky. They were captured together, from horizon to horizon, in the night sky above Loomberah, New South Wales, Australia by astronomer Gordon Garradd. Garradd used a home made all-sky camera with a fisheye lens, resulting in a circular 200 degree field of view. This gorgeous sky view was dominated by the luminous band of our Milky Way Galaxy cut by dramatic, dark interstellar dust clouds. Along with the bright stars of our Galaxy, the Large Magellanic Cloud is visible at the lower left. That night sky was also graced by the long, lovely, bluish tail of Comet Hyakutake, which can be seen toward the top of the image, near the bright star Arcturus. Bright city lights from nearby Tamworth glow along the Northwestern horizon.

2001 Put on your red/blue glasses and gaze into this dramatic stereo view from the surface of the Moon! Inspired by last Saturday's APOD, experimentor Patrick Vantuyne offers this stereo rendering of Apollo 12 astronaut Pete Conrad visiting the Surveyor 3 spacecraft in November of 1969. To create the stereo image, Vantuyne carefully combed through the pictures available for downloading from the Apollo Lunar Surface Journal web site to find two which would make an appropriate "stereo pair". He found a pair that depicted the captivating scene from only slightly different viewpoints, approximating the separation between human eyes. Combining the two separate pictures, one tinted red and the other blue-green, with the correct offset, produces the stereo effect when viewed using red/blue glasses, the red filter covering the left eye. The color filters guide each eye to see only the picture with the correct corresponding viewpoint and the brain interprets the result as normal stereo vision. (Editor's note: While you've got those glasses on ... other web sources of astronomy and space science stereo images include the Mars Path Finder archive and a 3D Tour of the Solar System.)

2000 On February 10th, an evocative evening sky above Rocklin, California, USA inspired astrophotographer Steve Sumner to record this remarkable sight - five planets and the Moon. Near its first quarter phase, the bright Moon was intentionally overexposed but Saturn, Jupiter, Mars, and Mercury (and, of course, planet Earth's horizon) are all clearly visible in the deepening twilight. Notably absent in this grouping of naked-eye planets is Venus which is still putting in an early appearance as the morning star. This month, Mercury has joined Venus in the dawn twilight while Saturn, Jupiter, and Mars still shine brightly in the western sky at nightfall making another gorgeous close grouping with the crescent Moon.

1999 Add another 8-meter telescope to the list of modern optical telescope giants. Kueyen achieved a first-light photograph of a bright star on March 1, ahead of schedule. The above picture of spiral galaxy NGC 2997 was taken with Antu, the first of the four planned Very Large Telscopes (VLTs) being built in Chile for the European Southern Observatory. NGC 2997 is a thin spiral galaxy tilted about 45 degrees with a bright compact nucleus and prominent lanes of dark dust.

1998 Which way to the interstate? What appears to be a caricature of a complex highway system on Earth is actually a system of ridges and cracks on the icy surface of Jupiter's moon Europa. The distance between parallel ridges in the above photograph is typically about 1 kilometer. The complexity of the cracks and ridges tell a story of Europa's past that is mostly undecipherable -- planetary geologists try to understand just the general origin of the overall features. One noteworthy feature is the overall white sheen, possibly indicating the presence of frost. Another is the dark centers between parallel ridges, which might indicate that dirty water from an underground ocean recently welled up in the cracks and froze.

1997 Jupiter's thick atmosphere is striped by wind-driven cloud bands that remain fixed in latitude - dark colored bands are known as belts while light colored bands are zones. At Jupiter's belt-zone boundaries the shearing wind velocities can reach nearly 300 miles per hour. Near infrared images recently returned by the Galileo Spacecraft were mapped to visible colors in this close-up of a belt-zone boundary near the gas giant's equator. The color mapping reveals different layers, lower clouds are bluish, higher ones pinkish. The smallest features seen are tens of miles across.

1996 The first module of the Russian Space Agency's Mir Space Station was launched into orbit 10 years ago (on February 20, 1986). Mir has since been substantially expanded in orbit by adding additional modules including the Kvant Astrophysics Module (1987) and recently a docking module. NASA's Space Shuttle Atlantis was modified to allow it to dock with Mir in 1995 (STS-71,, STS 74) beginning a series of Shuttle-Mir flights scheduled to continue through 1997. In this wide angle view - poised above planet Earth with sunlight glinting from solar panels - Mir and Atlantis are seen connected via the docking module from the perspective of the shuttle payload bay. The image is from an IMAX movie frame taken during the STS 74 mission. In late 1997, building on this jointly developed understanding and experience, the US and Russia will launch the first modules of the International Space Station.

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