V838 Mon: Echoes from the Edge
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Variable star V838 Monocerotis lies near the edge of our Milky Way Galaxy, about 20,000 light-years from the Sun. Still, ever since a sudden outburst was detected in January 2002, this enigmatic star has taken the center of an astronomical stage. As astronomers watch, light from the outburst echoes across pre-existing dust shells around V838 Mon, progressively illuminating ever more distant regions. This stunning image of swirls of dust surrounding the star was recorded by the Hubble Space Telescope in September of this year. The picture spans about 14 light-years. Astronomers expect the expanding echoes to continue to light up the dusty environs of V838 Mon for at least the rest of the current decade. Researchers have now found that V838 Mon is likely a young binary star, but the cause of its extraordinary outburst remains a mystery.
2006-11-03
Aurora over Clouds
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Auroras usually occur high above the clouds. The auroral glow is created when fast-moving particles ejected from the Sun impact the Earth's magnetosphere, from which charged particles spiral along the Earth's magnetic field to strike atoms and molecules high in the Earth's atmosphere. An oxygen atom, for example, will glow in the green light commonly emitted by an aurora after being energized by such a collision. The lowest part of an aurora will typically occur about 100 kilometers up, while most clouds exist only below about 10 kilometers. The relative heights of clouds and auroras are shown clearly in the featured picture in 2015 from Dyrholaey, Iceland. There, a determined astrophotographer withstood high winds and initially overcast skies in an attempt to capture aurora over a picturesque lighthouse, only to take, by chance, the featured picture including elongated lenticular clouds, along the way. Follow APOD on Instagram in: English, Farsi, Indonesian, Persian, or Portuguese
2021-05-30 Daniele Boffelli
Sunrise Solstice at Stonehenge
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Today the Sun reaches its northernmost point in the planet Earth's sky. Called a solstice, the date traditionally marks a change of seasons -- from spring to summer in Earth's Northern Hemisphere and from fall to winter in Earth's Southern Hemisphere. Pictured above is the 2005 Summer Solstice celebration at Stonehenge in England. The event was rare because Stonehenge was not always open to the public, and because recent summer solstices there had been annoyingly cloudy. In 2005, however, thousands of people gathered at sunrise to see the sun rise through the 4,000 year old solar monument. Even given the precession of the Earth's rotational axis over the millennia, the Sun continues to rise over Stonehenge in an astronomically significant way. In fact, the photographer was able to find a good spot where the rising Sun appeared over one of Stonehenge's massive standing stones.
2006-06-21 Pete Strasser (Tucson, Arizona, USA)
A Cliff Looming on Comet 67P
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What's that looming behind this gravel-strewn hill on Comet Churyumov�Gerasimenko? A jagged cliff. The unusual double-lobed nucleus of Comet 67P/Churyumov�Gerasimenko lends itself to unusual and dramatic vistas, another of which has been captured by the Rosetta spacecraft that arrived at the comet last September. The featured cometscape, taken last October and digitally enhanced, spans about 850 meters across. Meanwhile, Comet Churyumov�Gerasimenko continues to sprout jets as it nears its closest approach to the Sun in August. Along the way, Rosetta will continue listening for signals from Philae, a probe that landed on the nucleus but rebounded to an unknown surface location last November. If newly exposed to sunlight, Philae might regain enough energy to again signal Rosetta. Click Through the Universe: Random APOD Generator
2015-05-20
NGC 6888: The Crescent Nebula
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NGC 6888, also known as the Crescent Nebula, is a cosmic bubble about 25 light-years across, blown by winds from its central, bright, massive star. This beautiful portrait of the nebula is from the Isaac Newton Telescope at Roque de los Muchachos Observatory in the Canary Islands. It combines a composite color image with narrow band data that isolates light from hydrogen and oxygen atoms in the wind-blown nebula. The oxygen atoms produce the blue-green hue that seems to enshroud the detailed folds and filaments. NGC 6888's central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun's mass every 10,000 years. The nebula's complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.
2009-09-15 Daniel López
An Unusual Vein of Deposited Rock on Mars
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What could create this unusual vein of rock on Mars? A leading hypothesis is that this thin rock layer dubbed "Homestake" was deposited by a running liquid -- like most mineral veins are here on Earth. And the running liquid of choice is water. Therefore, this mineral streak -- rich in calcium and sulfur -- is the latest in the growing body of evidence that part of Mars had a watery past. This, in turn, increases the speculation that Mars was once hospitable to life. Pictured above is a vista taken near the western rim of Endeavour Crater by the Opportunity rover currently exploring Mars. The inset image shows a close up of the recently discovered mineral vein. Browse or share: Latest lunar eclipse pictures
2011-12-12
Starbirth in the Lagoon Nebula Credit and Copyright:
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Stars are forming even today in the Lagoon Nebula. This bright nebula is visible in the constellation of Sagittarius with binoculars. The above photo is the result of a new sensitive camera being attached to one of the world's largest telescopes. Curtains of collapsing hydrogen are shown above in green, highlighted by a special filter that isolates light from this specific atom. Many young stars are evident in the open cluster M8 in the Lagoon, the result of previously collapsed gas clouds. Many of the stars appear red because of the high amount of dust in the Lagoon Nebula. Red light penetrates dust clouds best, although enough dust will block all visible light and leave a dark nebula.
1996-10-24Illustris Simulation of the Universe
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How did we get here? Click play, sit back, and watch. A computer simulation of the evolution of the universe provides insight into how galaxies formed and perspectives into humanity's place in the universe. The Illustris project exhausted 20 million CPU hours in 2014 following 12 billion resolution elements spanning a cube 35 million light years on a side as it evolved over 13 billion years. The simulation tracks matter into the formation of a wide variety of galaxy types. As the virtual universe evolves, some of the matter expanding with the universe soon gravitationally condenses to form filaments, galaxies, and clusters of galaxies. The featured video takes the perspective of a virtual camera circling part of this changing universe, first showing the evolution of dark matter, then hydrogen gas coded by temperature (0:45), then heavy elements such as helium and carbon (1:30), and then back to dark matter (2:07). On the lower left the time since the Big Bang is listed, while on the lower right the type of matter being shown is listed. Explosions (0:50) depict galaxy-center supermassive black holes expelling bubbles of hot gas. Interesting discrepancies between Illustris and the real universe have been studied, including why the simulation produced an overabundance of old stars.
2020-02-23
Edge-on NGC 3628
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Sharp telescopic views of magnificent edge-on spiral galaxy NGC 3628 show a puffy galactic disk divided by dark dust lanes. The tantalizing scene puts many astronomers in mind of its popular moniker, The Hamburger Galaxy. About 100,000 light-years across and 35 million light-years away in the constellation Leo, NGC 3628 shares its neighborhood in the local Universe with two other large spirals, a grouping otherwise known as the Leo Triplet. Gravitational interactions with its cosmic neighbors are likely responsible for the extended flare and warp of this spiral's disk, populated by the galaxy's young blue star clusters and tell tale pinkish star forming regions. Also a result of past close encounters, a faint tidal tail of material is just visible extending upward and left in this deep galaxy portrait.
2011-11-04 Stephen Leshin
Supernova Remnant E0102-72 from Radio to X-Ray
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Not all stars form a big Q after they explode. The shape of supernova remnant E0102-72, however, is giving astronomers a clue about how tremendous explosions disperse elements and interact with surrounded gas. The above image is a composite of three different photographs in three different types of light. Radio waves, shown in red, trace high-energy electrons spiraling around magnetic field lines in the shock wave expanding out from the detonated star. Optical light, shown in green, traces clumps of relatively cool gas that includes oxygen. X-rays, shown in blue, show relatively hot gas that has been heated to millions of degrees. This gas has been heated by an inward moving shock wave that has rebounded from a collision with existing or slower moving gas. This big Q currently measures 40 light-years across and was found in our neighboring SMC galaxy. Perhaps we would know even more if we could buy a vowel.
2000-04-14