Thursday, April 9, 2015

Kepler 78b: Earth Sized Planet Discovered

Kepler 78b: Earth Sized Planet Discovered: APOD: 2013 November 5 - Kepler 78b: Earth-Sized Planet Discovered


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2013 November 5


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Kepler-78b: Earth-Sized Planet Discovered

Illustration Credit: David A. Aguilar (CfA)
Explanation: Even though Kepler-78b is only slightly larger than the Earth, it should not exist. Its size is extraordinary only in the sense that it is the most similar in size to the Earth of any exoplanet yet directly discovered. Its orbit, however, is extraordinary in the sense that it circles a Sun-like star 40 times closer than planet Mercury. At such a scathing distance, even rock is liquid. Models of planet formation predict that no planet can form in such a close orbit, and models of planet evolution predict that Kepler-78b's orbit should decay -- dooming the planet to eventually merge with its parent star. Illustrated above in comparison with the Earth, Kepler-78b was discovered by eclipse with the Earth-trailing Kepler spacecraft and further monitored for subtle wobbles by the HARPS- North, a spectrograph attached to the 3.6-meter Telescopio Nazionale Galileo in the Canary Islands.

Eclipse at 44 000 Feet

Eclipse at 44 000 Feet: APOD: 2013 November 7 - Eclipse at 44,000 Feet


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2013 November 7


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Explanation: Timing was critical to catch this image of November 3rd's solar eclipse. But flying at 44,000 feet, intrepid eclipse chasers on a chartered jet traveling 500 miles per hour managed to intercept the the Moon's shadow. The remarkable flight made a perpendicular crossing of the central shadow track. Darkening the skies beyond the wing tip at that moment, the Moon's shadow was moving at some 8,000 miles per hour across the Atlantic Ocean, 600 miles southeast of Bermuda. After only an instant of totality, this snapshot captured the lunar disk in silhouette. Rays of sunlight shining past peaks and valleys along the lunar limb created the fleeting appearance of a glistening diamond ring.

Solar Eclipse from Uganda

Solar Eclipse from Uganda: APOD: 2013 November 8 - Solar Eclipse from Uganda


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2013 November 8


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Explanation: The Sun's disk was totally eclipsed for a brief 20 seconds as the Moon's dark umbral shadow raced across Pokwero in northwestern Uganda on November 3rd. So this sharp telescopic view of totality in clear skies from the central African locale was much sought after by eclipse watchers. In the inspiring celestial scene the Moon just covers the overwhelmingly bright photosphere, the lower, normally visible layer of the Sun's atmosphere. Extending beyond the photosphere, the reddish hydrogen alpha glow of the solar chromosphere outlines the lunar silhouette, fading into the Sun's tenuous, hot, outer atmosphere or corona. Planet-sized prominences reaching beyond the limb of the active Sun adorn the edges of the silhouette, including a cloud of glowing plasma separated from the chromosphere near the 1 o'clock position.

Comet Lovejoy with M44

Comet Lovejoy with M44: APOD: 2013 November 9 - Comet Lovejoy with M44


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2013 November 9


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Explanation: While anxiously waiting for Comet ISON to brighten further as it falls toward the Sun, northern skygazers can also find three other bright comets in the east before dawn. In fact, Comet Lovejoy C/2013 R1 is currently the morning sky's brightest. Only discovered in September and not a sungrazing comet, this Comet Lovejoy is nearing the edge of naked-eye visibility and might be spotted from very dark sky sites. Sporting a greenish coma and tail in this telescopic view taken on November 7, Comet Lovejoy is about 0.5 AU from our fair planet and 1.2 AU from the Sun. The comet is having a photogenic Messier moment, sweeping past well known star cluster M44, the Beehive in Cancer. Yellowish bright star Delta Cancri is near the bottom of the frame.

An Active Sun During a Total Eclipse

An Active Sun During a Total Eclipse: APOD: 2013 November 11 - An Active Sun During a Total Eclipse


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2013 November 11


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Explanation: Sometimes, a total eclipse of the Sun is an opportunity. Taking advantage of such, the above image shows the solar eclipse earlier this month as covered and uncovered by several different solar observatories. The innermost image shows the Sun in ultraviolet light as recorded over a few hours by the SWAP instrument aboard the PROBA2 mission in a sun-synchronous low Earth orbit. This image is surrounded by a ground-based eclipse image, reproduced in blue, taken from Gabon. Further out is a circularly blocked region used to artificially dim the central sun by the LASCO instrument aboard the Sun-orbiting SOHO spacecraft. The outermost image -- showing the outflowing solar corona -- was taken by LASCO ten minutes after the eclipse and shows an outflowing solar corona. Over the past few weeks, our Sun has been showing an unusually high amount of sunspots, CMEs, and flares -- activity that was generally expected as the Sun is currently going through Solar Maximum -- the busiest part of its 11 year solar cycle. The above resultant image is a picturesque montage of many solar layers at once that allows solar astronomers to better match up active areas on or near the Sun's surface with outflowing jets in the Sun's corona.

The Unexpected Tails of Asteroid P5

The Unexpected Tails of Asteroid P5: APOD: 2013 November 12 - The Unexpected Tails of Asteroid P5


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2013 November 12


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Explanation: What is happening to asteroid P/2013 P5? No one is sure. For reasons unknown, the asteroid is now sporting not one but six discernible tails. The above images were taken two months ago by the orbiting Hubble Space Telescope and show the rapidly changing dust streams. It is not even known when P5 began displaying such unusual tails. Were the main belt asteroid struck by a large meteor, it would be expected to sport a single dust tail. Possible explanations include that light pressure from the Sun is causing the asteroid to rotate increasingly rapidly, which in turn causes pools of previously gravity-bound dust to spin off. Future observations should better indicate how P5 and its dust plumes are evolving and so provide more clues to its nature -- and to how many similar asteroids might exist.

In the Shadow of Saturn

In the Shadow of Saturn: APOD: 2013 November 13 - In the Shadow of Saturn


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2013 November 13


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Explanation: In the shadow of Saturn, unexpected wonders appear. The robotic Cassini spacecraft now orbiting Saturn drifted in giant planet's shadow earlier this year and looked back toward the eclipsed Sun. Cassini saw a unique and celebrated view. First, the night side of Saturn is seen to be partly lit by light reflected from its own majestic ring system. Next, Saturn's expansive ring system appears as majestic as always even from this odd angle. Ring particles, many glowing only as irregular crescents, slightly scatter sunlight toward Cassini in this natural color image. Several moons and ring features are also discernible. Appearing quite prominently is Saturn's E ring, the ring created by the unusual ice-fountains of the moon Enceladus and the outermost ring visible above. To the upper left, far in the distance, are the planets Mars and Venus. To the lower right, however, is perhaps the most wondrous spectacle of all: the almost invisible, nearly ignorable, pale blue dot of Earth.

The Jets of NGC 1097

The Jets of NGC 1097: APOD: 2013 November 14 - The Jets of NGC 1097


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2013 November 14


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Explanation: Enigmatic spiral galaxy NGC 1097 shines in southern skies, about 45 million light-years away in the chemical constellation Fornax. Its blue spiral arms are mottled with pinkish star forming regions in this colorful galaxy portrait. They seem to have wrapped around a small companion galaxy below and left of center, about 40,000 light-years from the spiral's luminous core. That's not NGC 1097's most peculiar feature, though. The very deep exposure hints of faint, mysterious jets, most easily seen to extend well beyond the bluish arms toward the lower right. In fact, four faint jets are ultimately recognized in optical images of NGC 1097. The jets trace an X centered on the galaxy's nucleus, but probably don't originate there. Instead, they could be fossil star streams, trails left over from the capture and disruption of a much smaller galaxy in the large spiral's ancient past. A Seyfert galaxy, NGC 1097's nucleus also harbors a supermassive black hole.

The Flash Spectrum of the Sun

The Flash Spectrum of the Sun: APOD: 2013 November 15 - The Flash Spectrum of the Sun


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2013 November 15


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Explanation: In a flash, the visible spectrum of the Sun changed from absorption to emission on November 3rd, during the brief total phase of a solar eclipse. That fleeting moment is captured by telephoto lens and diffraction grating in this well-timed image from clearing skies over Gabon in equatorial Africa. With overwhelming light from the Sun's disk blocked by the Moon, the normally dominant absorption spectrum of the solar photosphere is hidden. What remains, spread by the diffraction grating into the spectrum of colors to the right of the eclipsed Sun, are individual eclipse images at each wavelength of light emitted by atoms along the thin arc of the solar chromosphere. The brightest images, or strongest chromospheric emission lines, are due to Hydrogen atoms that produce the red hydrogen alpha emission at the far right and blue hydrogen beta emission to the left. In between, the bright yellow emission image is caused by atoms of Helium, an element only first discovered in the flash spectrum of the Sun.

Active Comet ISON

Active Comet ISON: APOD: 2013 November 16 - Active Comet ISON


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2013 November 16
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Explanation: Falling through planet Earth's predawn skies toward its close encounter with the Sun on November 28, Comet ISON is coming to life. The much anticipated comet has now been reported to have substantially increased in activity, surging to naked-eye visibility for dark sites and sprouting a more complex tail. ISON's tail stretches over two degrees in this telephoto skyview from southern Kenya, captured on the morning of November 14. Shown in two panels, the enlarged negative version on the right makes details of the long tail easier to trace, including the tail's separated filaments toward the top of the frame. A sungrazer and first time visitor to the inner solar system, the possibility of ISON's survival to become a bright comet in planet Earth's December skies remains a question.

The Magnificent Tail of Comet McNaught

The Magnificent Tail of Comet McNaught: APOD: 2013 November 17 - The Magnificent Tail of Comet McNaught


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2013 November 17


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Explanation: Comet McNaught, the Great Comet of 2007, grew a spectacularly long and filamentary tail. The magnificent tail spread across the sky and was visible for several days to Southern Hemisphere observers just after sunset. The amazing tail showed its greatest extent on long-duration, wide-angle camera exposures. During some times, just the tail itself estimated to attain a peak brightness of magnitude -5 (minus five), was caught by the comet's discoverer in the above image just after sunset in January 2007 from Siding Spring Observatory in Australia. Comet McNaught, the brightest comet in decades, then faded as it moved further into southern skies and away from the Sun and Earth. Within the next two weeks of 2013, rapidly brightening Comet ISON might sprout a tail that rivals even Comet McNaught.

Aurora and Unusual Clouds Over Iceland

Aurora and Unusual Clouds Over Iceland: APOD: 2013 November 18 - Aurora and Unusual Clouds Over Iceland


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2013 November 18


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Explanation: What's happening in the sky? On this cold winter night in Iceland, quite a lot. First, in the foreground, lies the largest glacier in Iceland: Vatnajokull. On the far left, bright green auroras appear to emanate from the glacier as if it was a volcano. Aurora light is reflected by the foreground lake Jökulsárlón. On the far right is a long and unusual lenticular cloud tinged with green light emitted from another aurora well behind it. Just above this lenticular cloud are unusual iridescent lenticular clouds displaying a broad spectral range of colors. Far beyond the lenticular is the setting Moon, while far beyond even the Moon are setting stars. The above image was captured in late March of 2012.

Globular Cluster M15 from Hubble

Globular Cluster M15 from Hubble: APOD: 2013 November 19 - Globular Cluster M15 from Hubble


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2013 November 19
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Explanation: Stars, like bees, swarm around the center of bright globular cluster M15. This ball of over 100,000 stars is a relic from the early years of our Galaxy, and continues to orbit the Milky Way's center. M15, one of about 170 globular clusters remaining, is noted for being easily visible with only binoculars, having at its center one of the densest concentrations of stars known, and containing a high abundance of variable stars and pulsars. Released only recently, this sharp image taken by the Earth-orbiting Hubble Space Telescope spans about 120 light years. It shows the dramatic increase in density of stars toward the cluster's center. M15 lies about 35,000 light years away toward the constellation of the Winged Horse (Pegasus).

Heavy Black Hole Jets in 4U1630 47

Heavy Black Hole Jets in 4U1630 47: APOD: 2013 November 20 - Heavy Black Hole Jets in 4U1630-47


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2013 November 20


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Heavy Black Hole Jets in 4U1630-47

Illustration Credit: NASA, CXC, M. Weiss
Explanation: What are black hole jets made of? Many black holes in stellar systems are surely surrounded by disks of gas and plasma gravitationally pulled from a close binary star companion. Some of this material, after approaching the black hole, ends up being expelled from the star system in powerful jets emanating from the poles of the spinning black hole. Recent evidence indicates that these jets are composed not only electrons and protons, but also the nuclei of heavy elements such as iron and nickel. The discovery was made in system 4U1630-47 using CSIRO’s Compact Array of radio telescopes in eastern Australia, and the European Space Agency's Earth-orbiting XMM-Newton satellite. The 4U1630-47 star system is depicted above in an artist's illustration, with a large blue star on the right and jets emanating from a black hole in the center of the accretion disc on the left. Although the 4U1630-47 star system is thought to contain only a small black hole -- a few times the mass of our Sun -- the implications of the results may be larger: that black holes of larger sizes might also be emitting jets of massive nuclei into the cosmos.

The Trail of a Minotaur

The Trail of a Minotaur: APOD: 2013 November 21 - The Trail of a Minotaur


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2013 November 21
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Explanation: Star trails arc above a moonlit beach and jetty in this serene sea and night skyscape. Captured on November 19, the single time exposure looks south down the Atlantic coast from Cape Cod, Massachusetts, USA. But the longest and brightest trail is a Minotaur 1 rocket, a stage separation and exhaust plume visible along the rocket's fiery path toward low Earth orbit. The multi-stage Minotaur was launched from the Mid-Atlantic Regional Spaceport at NASA's Wallops Flight Facility at 8:15 pm Eastern Time in Virginia, about 400 miles away. On board were a remarkable 29 satellites destined for low Earth orbit, including a small cubesat built by high school students, and Firefly.

From California to the Pleiades

From California to the Pleiades: APOD: 2013 November 22 - From California to the Pleiades


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2013 November 22
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Explanation: An astronomical trip from the California Nebula to the Pleiades star cluster would cover just over 12 degrees across planet Earth's night sky. That's equivalent to the angular extent of 25 Full Moons, as your telescope sweeps past the borders of the constellations Perseus and Taurus. This wide and deep mosaic image of the region explores the cosmic landscape's dusty nebulae and colors otherwise too faint for your eye to see. On the left, cataloged as NGC 1499, the California Nebula does have a familiar shape, though its coastline is actually over 60 light-years long and lies about 1,500 light-years away. The nebula's pronounced reddish glow is from hydrogen atoms ionized by luminous blue star Xi Persei seen just to its right. At the far right, the famous Pleiades star cluster is some 400 light-years distant and around 15 light-years across. Its spectacular blue color is due to the reflection of starlight by interstellar dust. In between are hot stars of the Perseus OB2 association and dusty, dark nebulae along the edge of the nearby, massive Perseus molecular cloud.

Comet ISON from STEREO

Comet ISON from STEREO: APOD: 2013 November 23 - Comet ISON from STEREO


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2013 November 23
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Explanation: Still intact, on November 21 Comet ISON (C/2012 S1) swept into this animated field of view (left) from the HI-1 camera on the STEREO-A spacecraft. The camera has also captured periodic Comet Encke, Mercury, and Earth, with the Sun cropped out of the frame at the right, the source of the billowing solar wind. From STEREO's perspective in interplanetary space, planet Earth is actually the most distant of the group, seen in its orbit beyond the Sun. Mercury is closest, but both planets are still so bright they create sharp vertical lines in the camera's detector. Both comets clearly sport substantial tails, but ISON is closer to the camera and will continue to move more rapidly through the field. Cameras on STEREO and SOHO spacecraft will be able to follow Comet ISON as it falls towards its close encounter with the Sun on November 28, even as ISON gets more difficult to see in the bright dawn skies of planet Earth.

Comet Hale Bopp Over Indian Cove

Comet Hale Bopp Over Indian Cove: APOD: 2013 November 24 - Comet Hale Bopp Over Indian Cove


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2013 November 24


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Explanation: Comet Hale-Bopp, the Great Comet of 1997, was quite a sight. In the above photograph taken on 1997 April 6, Comet Hale-Bopp was imaged from the Indian Cove Campground in the Joshua Tree National Park in California, USA. A flashlight was used to momentarily illuminate foreground rocks in this six minute exposure. An impressive blue ion tail was visible above a sunlight-reflecting white dust tail. Comet Hale-Bopp remained visible to the unaided eye for over a year before returning to the outer Solar System and fading. As Comet ISON approaches the Sun this week, sky enthusiasts around the Earth are waiting to see if its tails will become even more spectacular than those displayed by Comet Hale-Bopp.

Anemic Spiral NGC 4921 from Hubble

Anemic Spiral NGC 4921 from Hubble: APOD: 2013 November 25 - Anemic Spiral NGC 4921 from Hubble


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2013 November 25


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Explanation: How far away is spiral galaxy NGC 4921? Although presently estimated to be about 310 million light years distant, a more precise determination could be coupled with its known recession speed to help humanity better calibrate the expansion rate of the entire visible universe. Toward this goal, several images were taken by the Hubble Space Telescope in order to help identify key stellar distance markers known as Cepheid variable stars. Since NGC 4921 is a member of the Coma Cluster of Galaxies, refining its distance would also allow a better distance determination to one of the largest nearby clusters in the local universe. The magnificent spiral NGC 4921 has been informally dubbed anemic because of its low rate of star formation and low surface brightness. Visible in the above image are, from the center, a bright nucleus, a bright central bar, a prominent ring of dark dust, blue clusters of recently formed stars, several smaller companion galaxies, unrelated galaxies in the far distant universe, and unrelated stars in our Milky Way Galaxy.

Cap Cloud over the Sierra Nevadas

Cap Cloud over the Sierra Nevadas: APOD: 2013 November 26 - Cap Cloud over the Sierra Nevadas


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2013 November 26


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Explanation: One might say this was a bell weather day for the Sierra Nevada mountains. In January, just as the Sun was setting above the district of Albayzín in Grenada, Spain, a huge cloud appeared as a bell capping the Veleta peak. Such a Cap cloud is formed by air forced upwards by a mountain peak, with the air then cooling, saturating with moisture, and finally having its molecular water condense into cloud droplets. Such a bell-shaped cloud structure is unusual as air typically moves horizontally, making most clouds nearly flat across at the bottom. Vertical waves can also give additional lenticular cloud layers, as also seen above. Given the fleeting extent of the great cloud coupled with momentarily excellent sunset coloring, one might considered this also a bellwether day for an accomplished photographer.

Comet ISON Rising

Comet ISON Rising: APOD: 2013 November 27 - Comet ISON Rising


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2013 November 27
Explanation: Will Comet ISON survive tomorrow's close encounter with the Sun? Approaching to within a solar diameter of the Sun's surface, the fate of one of the most unusual comets of modern times will finally be determined. The comet could shed a great amount of ice and dust into a developing tail -- or break apart completely. Unfortunately, the closer Comet ISON gets to the Sun, the harder it has been for conventional telescopes to see the brightening comet in the glare of the morning Sun. Pictured in the above short time lapse video, Comet ISON was captured rising over the Canary Islands just above the morning Sun a few days ago. If the comet's nucleus survives, the coma and the tails it sheds might well be visible rising ahead of the Sun in the next few days or weeks. Alternatively, satellites watching the Sun might document one of the larger comet disintegrations yet recorded. Stay tuned!

NGC 1999: South of Orion

NGC 1999: South of Orion: APOD: 2013 November 28 - NGC 1999: South of Orion


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2013 November 28


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Explanation: South of the large star-forming region known as the Orion Nebula, lies bright blue reflection nebula NGC 1999. At the edge of the Orion molecular cloud complex some 1,500 light-years distant, NGC 1999's illumination is provided by the embedded variable star V380 Orionis. That nebula is marked with a dark sideways T-shape near center in this cosmic vista that spans about 10 light-years. The dark shape was once assumed to be an obscuring dust cloud seen in silhouette against the bright reflection nebula. But recent infrared images indicate the shape is likely a hole blown through the nebula itself by energetic young stars. In fact, this region abounds with energetic young stars producing jets and outflows with luminous shock waves. Cataloged as Herbig-Haro (HH) objects, named for astronomers George Herbig and Guillermo Haro, the shocks look like red gashes in this scene that includes HH1 and HH2 just below NGC 1999. The stellar jets push through the surrounding material at speeds of hundreds of kilometers per second.

Comet ISON Before and After

Comet ISON Before and After: APOD: 2013 November 29 - Comet ISON Before and After


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2013 November 29


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Comet ISON Before and After

Image Credit: NASA, SOHO
Explanation: Sungrazing Comet ISON reached perihelion, its closest approach to the Sun, yesterday, November 28, at 18:45 UT. The comet passed just over 1 million kilometers above the solar surface, a distance less than the diameter of the Sun. These two panels follow ISON before (right) and after its close approach, imaged by the LASCO instrument onboard the Sun staring SOHO spacecraft. Overwhelming sunlight is blocked by LASCO's central occulting disk with a white circle indicating the Sun's positon and scale. The bright comet is seen along its path at the bottom of the before panel, but something much fainter exits near the top of the after panel, potentially a dust tail reforming from the debris left from ISON's perihelion passage.

A Laser Strike at the Galactic Center

A Laser Strike at the Galactic Center:

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2013 December 1


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Explanation: Why are these people shooting a powerful laser into the center of our Galaxy? Fortunately, this is not meant to be the first step in a Galactic war. Rather, astronomers at the Very Large Telescope (VLT) site in Chile are trying to measure the distortions of Earth's ever changing atmosphere. Constant imaging of high-altitude atoms excited by the laser -- which appear like an artificial star -- allow astronomers to instantly measure atmospheric blurring. This information is fed back to a VLT telescope mirror which is then slightly deformed to minimize this blurring. In this case, a VLT was observing our Galaxy's center, and so Earth's atmospheric blurring in that direction was needed. As for inter-galaxy warfare, when viewed from our Galaxy's center, no casualties are expected. In fact, the light from this powerful laser would combine with light from our Sun to together appear only as bright as a faint and distant star.