APOD: 2021 November 28 - A High Cliff on Comet Churyumov Gerasimenko Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 28 A High Cliff on Comet Churyumov-Gerasimenko Image Credit & Licence: ESA, Rosetta spacecraft, NAVCAM; Additional Processing: Stuart Atkinson Explanation: This high cliff occurs not on a planet, not on a moon, but on a comet.It was discovered to be part of the dark nucleus of Comet Churyumov-Gerasimenko (CG) by Rosetta, a robotic spacecraft launched by ESA that rendezvoused with the Sun-orbiting comet in 2014. The ragged cliff, as featured here, was imaged by Rosetta in 2014.Although towering about one kilometer high, the low surface gravity of Comet CG would likely make it an accessible climb -- and even a jump from the cliff survivable. At the foot of the cliff is relatively smooth terrain dotted with boulders as large as 20 meters across.Data from Rosetta indicates that the ice in Comet CG has a significantly different deuterium fraction -- and hence likely a different origin -- than the water in Earth's oceans. Rosetta ended its mission with a controlled impact onto Comet...

APOD: 2021 November 27 - Messier 101 Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 27 Messier 101 Image Credit: NASA,ESA,CFHT,NOAO;Acknowledgement -K.Kuntz (GSFC),F.Bresolin (U.Hawaii),J.Trauger (JPL),J.Mould (NOAO),Y.-H.Chu (U. Illinois) Explanation: Big, beautiful spiral galaxy M101 is one of the last entries inCharles Messier'sfamous catalog, but definitely notone of the least.About 170,000 light-years across, this galaxy is enormous, almosttwice the size of our own Milky Way.M101 was also one of the originalspiral nebulaeobserved by Lord Rosse's large 19th century telescope, theLeviathanof Parsontown.Assembled from 51 exposures recorded by theHubble Space Telescopein the 20th and 21stcenturies, with additional data from ground based telescopes,this mosaic spans about 40,000 light-years across the central regionof M101 in one of the highest definitionspiral galaxy portraits ever released from Hubble.The sharp image shows stunning featuresof the galaxy's face-on disk of stars and dust along withbackground galaxies, some visible right through M101 itself.Also known as thePinwheel Galaxy, M101lies within the boundaries of the northern constellationUrsa Major, about 25 million light-years away. Tomorrow's picture: Churyumov-Gerasimenko<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell...

APOD: 2021 November 26 - Great Refractor and Lunar Eclipse Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 26 Great Refractor and Lunar Eclipse Image Credit &Copyright:Laurie Hatch Explanation: Rain clouds passedand the dome of the Lick Observatory's 36 inch Great Refractoropened on November 19.The historic telescopewas pointed toward a partially eclipsed Moon.Illuminated by dim red lighting to preserve an astronomer'snight vision,telescope controls, coordinate dials, andthe refractor's 57 foot long barrel werecaptured in this high dynamic range image.Visible beyond the foreshortened barrel and dome slit,growing brighter after itsalmost total eclipse phase,the lunar disk created a colorful corona through lingering clouds.From the open dome, the view of theclearing sky above includes the Pleiades star clusterabout 5 degrees fromMoon and Earth's shadow. Notable APOD Submissions: Lunar Eclipse of 2021 November 19 Tomorrow's picture: M101<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)NASA Official: Phillip NewmanSpecific rights apply.NASA WebPrivacy Policy and Important NoticesA service of:ASD atNASA /GSFC& Michigan Tech. U.

APOD: 2021 November 25 - At the Shadow's Edge Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 25 At the Shadow's Edge Image Credit &Copyright:Jean-Francois Gout Explanation: Shaped like a cone tapering into space, the Earth's darkcentral shadow or umbrahas a circular cross-section.It's wider than the Moon at the distance ofthe Moon's orbit though.Butduring the lunar eclipseof November 18/19, part ofthe Moon remained just outside the umbral shadow.The successive picturesin this composite of 5 images from thatalmost total lunar eclipsewere taken over a period of about 1.5 hours.The series is aligned to trace part of the cross-section'scirculararc, with the central image at maximum eclipse.It shows a bright, thin sliver of the lunar disk still beyondthe shadow's curved edge.Of course, even within the shadow the Moon's surface is not completelydark, reflecting the reddish hues of filtered sunlight scatteredinto the shadow by Earth's atmosphere. Notable APOD Submissions: Lunar Eclipse of 2021 November 19 Tomorrow's picture: pixels in space<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)NASA Official: Phillip NewmanSpecific rights apply.NASA WebPrivacy Policy...

APOD: 2021 November 24 - Pleiades: The Seven Sisters Star Cluster Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 24 Pleiades: The Seven Sisters Star Cluster Image Credit & Copyright: Damien Cannane Explanation: Have you ever seen the Pleiades star cluster?Even if you have, you probably have never seen it as large and clear as this.Perhaps the most famous star cluster on the sky, the bright stars of the Pleiadescan be seen without binoculars from even the depths of alight-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident.The featured exposure, taken from Florida, USA,covers a sky area several times the size of the full moon. Also known as the Seven Sisters andM45,the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six of the sister stars visible to the unaided eye.The actual number of Pleiades stars visible, however, may be more or less...

APOD: 2021 November 23 - The Sun in X rays from NuSTAR Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 23 The Sun in X-rays from NuSTAR Image Credit: NASA,NuSTAR, SDO Explanation: Why are the regions above sunspots so hot?Sunspots themselves are a bit cooler than the surrounding solar surface because the magnetic fields that create them reduce convective heating. It is therefore unusual that regions overhead -- even much higher up in the Sun's corona -- can be hundreds of times hotter.To help find the cause, NASA directed the Earth-orbiting Nuclear Spectroscopic Telescope Array (NuSTAR) satellite to point its very sensitive X-ray telescope at the Sun.Featured here is the Sun in ultraviolet light, shown in a red hue as taken by the orbiting Solar Dynamics Observatory (SDO). Superimposed in false-colored green and blue is emission above sunspots detected by NuSTAR in different bands of high-energy X-rays, highlighting regions of extremely high temperature.Clues about the Sun's atmospheric heating mechanisms come from NuSTAR images like this and shed lighton solar nanoflares and microflares as brief bursts of energy that may drive the unusual heating....

APOD: 2021 November 22 - Lunar Eclipse over a Skyscraper Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 22 Lunar Eclipse over a Skyscraper Image Credit & Copyright: Yuri Beletsky(CarnegieLas Campanas Observatory,TWAN) Explanation: Why is the Moon on top of this building?Planning.It took the astrophotographer careful planning -- including figuring out exactly where to place the camera and exactly when to take the shot -- to create this striking superposition.The single image featured was taken in the early morning hours of November 19, near the peak of the partial lunar eclipse that was occurring as the Moon passed through the Earth's shadow. At this time, almost the entire Moon -- 99.1 percent of its area -- was in the darkest part of the Earth's shadow. The building is the Gran Torre Santiago building in Chile, the tallest building in South America. Although the entire eclipse lasted an impressive six hours, this image had to be taken within just a few seconds to get the alignment right -- the Earth's rotation soon moved the building out of alignment.The next Earth-Moon eclipse will be a...

APOD: 2021 November 21 - Introducing Comet Leonard Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 21 Introducing Comet Leonard Image Credit & Copyright: Dan Bartlett Explanation: Here comes Comet Leonard.Comet C/2021 A1 (Leonard) was discovered as a faint smudge in January 2021 when it was out past Mars -- but its orbit will take the giant shedding ice-ball into the inner Solar System, passing near both Earth and Venus in December before it swoops around the Sun in early January 2022.Although comets are notoriously hard to predict, some estimations have Comet Leonard brightening to become visible to theunaided eye in December. Comet Leonard was captured just over a week ago already sporting a green-tinged coma and an extended dust tail.The featured picture was composed from 62 images taken through a moderate-sized telescope -- one set of exposures tracking the comet, while another set tracking the background stars.The exposures were taken from the dark skies above the Eastern Sierras (Mountains), near June Lake in California, USA. Soon after passing near the Earth in mid-December, the comet will shift from northern to southern skies....

APOD: 2021 November 20 - An Almost Total Lunar Eclipse Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 20 An Almost Total Lunar Eclipse Image Credit &Copyright:Robert Fedez Explanation: Predawn hours of November 19 found the Moonin partly cloudy skies over Cancun, Mexico.Captured in thistelephoto snapshot,the lunar disk is not quite entirely immersed in Earth's darkumbral shadowduring a long partial lunar eclipse.The partial eclipse was deep though, deep enough to showthe dimmed but reddened light in Earth's shadow.That's a sightoften anticipated byfans of total lunar eclipses.Wandering through the constellation Taurus,the eclipsedMoon's dimmer lightalso made it easier to spot the Pleiades star cluster.The stars of theSeven Sistersshare this frame at the upper right, with thealmost totally eclipsed Moon. Notable APOD Submissions (so far): Lunar Eclipse of 2021 November 19 Tomorrow's picture: New Bright Comet?<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)NASA Official: Phillip NewmanSpecific rights apply.NASA WebPrivacy Policy and Important NoticesA service of:ASD atNASA /GSFC& Michigan Tech. U.

APOD: 2021 November 19 - NGC 281: Starless with Stars Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 19 NGC 281: Starless with Stars Image Credit &Copyright:Wido Oerlemans -X-ray: Chandra,Infrared: Spitzer Explanation: In visible light the stars have been removed from this narrow-band imageof NGC 281,a star forming region some 10,000 light-years away towardthe constellation Cassiopeia.Stars were digitally added back to the resultingstarless image though.But instead of using visible light image data, the stars were added withX-ray data(in purple) from the Chandra X-ray Observatory andinfrared data(in red) from the Spitzer Space Telescope.The mergedmultiwavelengthview reveals a multitude ofstars in the region's embedded star clusterIC 1590.The young stars are normally hidden in visible light images bythe natal cloud's gas and obscuring dust.Also known to backyard astro-imagers as thePacmanNebula for its overall appearance in visible light,NGC 281 is about 80 light-years across. Tomorrow's picture: light-weekend<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)NASA Official: Phillip NewmanSpecific rights apply.NASA WebPrivacy Policy and Important NoticesA service of:ASD atNASA /GSFC& Michigan Tech. U.

APOD: 2021 November 18 - Full Moonlight Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 18 Full Moonlight Image Credit &Copyright:Zhengjie Wu andJeff Dai(TWAN) Explanation: A photographer in silhouette stands in bright moonlight asthe Full Moon risesin this well-planned telephoto image.Of course, the Full Moon is normally the brightest lunar phase.But onNovember 18/19, the Full Moon's light will be dimmed during a deep partial lunar eclipseseen across much of planet Earth.At maximum eclipse only a few percent of the lunar disk's diameter shouldremain outside the Earth's dark umbral shadow when the Moon slidesclose to the shadow's southern edge.Near apogee, the farthest point in its orbit,the Moon's motion will be slow.That should make this secondlunar eclipse of 2021an exceptionally long partial lunar eclipse.For most ofNorth America the eclipse partial phaseswill be visible in predawn hours.Since eclipsestend to come in pairs, this lunar eclipse will be followed by asolar eclipse in two weeks on December 4. Tomorrow's picture: starless with stars<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)NASA Official: Phillip NewmanSpecific rights...

APOD: 2021 November 17 - NGC 3314: When Galaxies Overlap Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 17 NGC 3314: When Galaxies Overlap Image Credit: NASA, ESA, Hubble; Processing & Copyright: William Ostling (The Astronomy Enthusiast) Explanation: Why doesn't the nearby galaxy create a gravitational lensing effect on the background galaxy?It does, but since both galaxies are so nearby, the angular shift is much smaller than the angular sizes of the galaxies themselves. The featured Hubble image of NGC 3314 shows two large spiral galaxies which happen to line up exactly. The foreground spiral NGC 3314a appears nearly face-on with its pinwheel shape defined by young bright star clusters. Against the glow of the background galaxy NGC 3314b, though, dark swirling lanes of interstellar dust can also be seen tracing the nearer spiral's structure. Both galaxies appear on the edge of the Hydra Cluster of Galaxies, a cluster that is about 200 million light years away.Gravitational lens distortions are much easier to see when the lensing galaxy is smaller and further away.Then, the background galaxy may even be distorted into a ring...

APOD: 2021 November 16 - Geminids from Gemini Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 16 Geminids from Gemini Image Credit & Copyright: Wang Jin Explanation: Where are all of these meteors coming from? In terms of direction on the sky, the pointed answer is theconstellationof Gemini. That is why the major meteor shower in December is known as theGeminids -- because shower meteors all appear to come from aradiant toward Gemini.Three dimensionally, however,sand-sized debrisexpelled from the unusual asteroid 3200 Phaethonfollows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation of Gemini.Therefore, when Earth crosses this orbit, theradiant point of falling debris appears in Gemini.Featured here, a composite of many images taken during the 2020 Geminids meteor shower shows over 200 bright meteors thatstreakedthrough the sky during the night December 14. The best meteor shower in November, the Leonids, peaks tonight and tomorrow.Unfortunately, this year, dim meteors during the early-morning peak will be hard to see against a sky lit by a bright gibbous moon. Still, a few bright...

APOD: 2021 November 15 - Light Pillar over Volcanic Etna Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation w ritten by a professional astronomer. 2021 November 15 Light Pillar over Volcanic Etna Image Credit & Copyright: Giancarlo Tinè Explanation: What happening above that volcano?Something very unusual -- a volcanic light pillar.More typically, light pillars are caused by sunlight and so appear as a bright column that extends upward above a rising or setting Sun.Alternatively, other light pillars -- some quite colorful -- have been recorded above street and house lights.This light pillar, though, was illuminated by the red light emitted by the glowing magma of an erupting volcano.The volcano is Italy's Mount Etna, and the featured image was captured with a single shot a few hours after sunset in mid-June.Freezing temperatures above the volcano's ash cloud created ice-crystals either in cirrus clouds high above the volcano -- or in condensed water vapor expelled by Mount Etna.These ice crystals -- mostly flat toward the ground but fluttering -- then reflected away light from the volcano's caldera. Explore Your Universe: Random APOD Generator Tomorrow's picture: meteor flow <| Archive| Submissions | Index|...

APOD: 2021 November 14 - How to Identify that Light in the Sky Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation w ritten by a professional astronomer. 2021 November 14 How to Identify that Light in the Sky Illustration Credit & Copyright: HK (The League of Lost Causes) Explanation: What is that light in the sky?Perhaps one of humanity's more common questions, an answer may result from a few quick observations. For example -- is it moving or blinking?If so, and if you live near a city, the answer is typically an airplane, since planes are so numerous and so few stars and satellites are bright enough to be seen over the din of artificial city lights.If not, and if you live far from a city, that bright light is likely a planet such as Venus or Mars -- the former of which is constrained to appear near the horizon just before dawn or after dusk. Sometimes the low apparent motion of a distant airplane near the horizon makes it hard to tell from a bright planet, but even this can usually be discerned by the plane's motion over a...

APOD: 2021 November 13 - Rosetta s Comet in Gemini Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 13 Rosetta's Comet in Gemini Image Credit &Copyright:Rolando Ligustri(CARA Project,CAST) Explanation: Returning alongits 6.4 year orbit,periodic comet Churyumov-Gerasimenko (67P) is caught in thistelescopic frame from November 7.Sweeping past background stars in the constellation Geminithe comet's dusty tail stretches toward the upper right to Upsilon Geminorum.Also known as Pollux,Beta Geminorum, Gemini's brightest star,shines just off the upper left edge of the field-of-view.Churyumov-Gerasimenkoreached its 2021 perihelionor closest approach to the Sun on November 2.At perigee, its closest approach to planet Earth on November 12,this comet was about 0.42 astronomical units away,though it remains too faint to be seen by eye alone.The well-studied cometwas explored by robots from planet Earthduring its last trip through the inner solar system.It's now famous as the final resting place for the historicRosetta spacecraft and Philae lander. Tomorrow's picture: What that was.<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)NASA Official: Phillip NewmanSpecific rights apply.NASA WebPrivacy Policy and Important NoticesA service...

APOD: 2021 November 12 - M33: The Triangulum Galaxy Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 12 M33: The Triangulum Galaxy Image Credit &Copyright:Bernard Miller Explanation: The small, northern constellationTriangulumharbors this magnificent face-on spiral galaxy, M33.Its popular names include the Pinwheel Galaxy or justthe Triangulum Galaxy.M33 is over 50,000 light-years in diameter, third largest in theLocalGroup of galaxies after the Andromeda Galaxy (M31), and ourown Milky Way.About 3 million light-years from the Milky Way,M33 is itself thought to be a satellite of theAndromeda Galaxy andastronomersin these two galaxies would likely have spectacular views ofeach other's grand spiral star systems.As for the view from planet Earth,this sharp imageshows off M33's blue star clustersand pinkish star forming regions alongthe galaxy's loosely wound spiral arms.In fact, thecavernous NGC 604 is thebrightest star forming region, seen here at about the 4 o'clock positionfrom the galaxy center.Like M31, M33's population of well-measured variable starshave helped make this nearby spiral a cosmic yardstick forestablishingthe distancescale of the Universe. Tomorrow's picture: 67P<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU)...

APOD: 2021 November 11 - NGC 1333: Stellar Nursery in Perseus Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer. 2021 November 11 NGC 1333: Stellar Nursery in Perseus Image Credit &Copyright:Michael Sherick Explanation: NGC 1333 is seen in visible light asa reflection nebula,dominated by bluish hues characteristic of starlight reflected byinterstellar dust.A mere 1,000 light-years distant toward the heroic constellationPerseus,it lies at the edge of a large,star-formingmolecular cloud.This telescopic close-up spans about two full moons on the sky or just over15 light-years at the estimated distance of NGC 1333.It shows details of the dusty regionalong with telltale hints of contrasty red emission fromHerbig-Haroobjects, jets and shocked glowing gasemanating from recently formed stars.In fact, NGC 1333 contains hundreds of stars less thana million years old, most stillhidden from optical telescopesby the pervasive stardust.The chaotic environment may be similar to one in which our own Sunformed over 4.5 billion years ago. Tomorrow's picture: pixels in space<| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)NASA Official: Phillip NewmanSpecific rights apply.NASA WebPrivacy Policy and Important NoticesA service...

APOD: 2021 November 10 - Video of a Green Flash Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation w ritten by a professional astronomer. Video of a Green Flash Video Credit & Copyright: Paolo Lazzarotti Explanation: Many think it is just a myth. Others think it is true but its cause isn't known. Adventurers pride themselves on having seen it. It's a green flash from theSun. The truth is thegreen flashdoes exist and its cause is well understood. Just as the settingSun disappears completely from view,a last glimmer appears startlinglygreen. The effect is typically visible only from locations with a low,distant horizon, and lasts just a few seconds.A green flash is also visible for a risingSun, but takes better timing to spot. A dramaticgreen flash was caught on video last month as the Sun set beyond the Ligurian Sea from Tuscany, Italy.The second sequence in the featured video shows the green flash in real time, while the first is sped up and the last is in slow motion.The Sun itself does not turnpartly green -- the effect is caused by layers of theEarth's atmosphere acting like a prism. Discovery +...

APOD: 2021 November 9 - All of These Space Images are Fake Except One Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation w ritten by a professional astronomer. 2021 November 9 All of These Space Images are Fake Except One Image Credit: M. J. Smith et al. (U. Hertfordshire) Explanation: Why would you want to fake a universe?For one reason -- to better understand our real universe.Many astronomical projects seeking to learn properties of our universe now start with a robotic telescope taking sequential images of the night sky.Next, sophisticated computer algorithms crunch these digital images to find stars and galaxies and measure their properties. To calibrate these algorithms, it is useful to test them on fake images from a fake universe to see if the algorithms can correctly deduce purposely imprinted properties.The featured mosaic of fake images was created to specifically mimic the images that have appeared on NASA's Astronomy Picture of the Day (APOD). Only one image of the 225 images is real -- can you find it?The accomplished deceptors have made available individual fake APOD images that can be displayed by accessing their ThisIsNotAnAPOD webpage or Twitter...