APOD: 2021 October 21 - Sharpless 308: The Dolphin-head Nebula 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 October 21 SH2-308: The Dolphin-head Nebula Image Credit &Copyright:Nik Szymanek Explanation: Blown by fast winds from a hot, massive star,this cosmic bubble is huge.Cataloged asSharpless2-308 it lies some 5,000 light-years away toward the constellation ofthe Big Dog(CanisMajor) and covers slightly more of the sky than a Full Moon.Thatcorrespondsto a diameter of 60 light-years at its estimated distance.The massive star that created the bubble, aWolf-Rayet star,is the bright onenear the centerof the nebula.Wolf-Rayet stars have over 20 times the mass of the Sunand are thought to be in a brief,pre-supernova phaseof massive star evolution.Fast winds from this Wolf-Rayet starcreate the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution.The windblown nebula has an age of about 70,000years.Relatively faint emission captured by narrowband filters in the deep imageis dominated by the glow of ionized oxygen atomsmapped toa blue hue.Presenting amostly harmlessoutline, SH2-308 is also known as The Dolphin-head Nebula. Tomorrow's picture: it's a comet<| Archive| Submissions | Index| Search| Calendar| RSS| Education|...

APOD: 2021 October 20 - Lucy Launches to Eight Asteroids 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 October 20 Lucy Launches to Eight Asteroids Image Credit & Copyright: John Kraus Explanation: Why would this mission go out as far as Jupiter -- but then not visit Jupiter?Lucy's plan is to follow different leads about the origin of our Solar System than can be found at Jupiter -- where Juno now orbits.Jupiter is such a massive planet that its gravity captures numerous asteroids that orbit the Sun ahead of it -- and behind.These trojan asteroids formed all over our Solar System and some may have been trapped there for billions of years.Flying by these trojan asteroids enables studying them as fossils that likely hold unique clues about our early Solar System.Lucy, named after a famous fossil skeleton which was named after a famous song, is scheduled to visit eight asteroids from 2025 to 2033. Pictured, Lucy's launch was captured with reflection last week aboard a powerful Atlas V rocket from Cape Canaveral, Florida, USA. Tomorrow's picture: mostly harmless <| Archive| Submissions | Index| Search|...

APOD: 2021 October 19 - Palomar 6: Globular 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 October 19 Palomar 6: Globular Star Cluster Image Credit: ESA/Hubble and NASA, R. Cohen Explanation: Where did this big ball of stars come from?Palomar 6 is one of about 200 globular clusters of stars that survive in our Milky Way Galaxy.These spherical star-balls are older than our Sun as well as older than most stars that orbit in our galaxy's disk. Palomar 6 itself is estimated to be about 12.5 billion years old, so old that it is close to -- and so constrains -- the age of the entire universe. Containing about 500,000 stars, Palomar 6 lies about 25,000 light years away, but not very far from our galaxy's center. At that distance, this sharp image from the Hubble Space Telescope spans about 15 light-years. After much study including images from Hubble, a leading origin hypothesis is that Palomar 6 was created -- and survives today -- in the central bulge of stars that surround the Milky Way's center, not in the distant galactic halo...

APOD: 2021 October 18 - Earthshine Moon over Sicily 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 October 18 Earthshine Moon over Sicily Image Credit & Copyright: Dario Giannobile Explanation: Why can we see the entire face of this Moon? When the Moon is in a crescent phase, only part of it appears directly illuminated by the Sun. The answer is earthshine, also known as earthlight and the da Vinci glow. The reason is that the rest of the Earth-facing Moon is slightly illuminated by sunlight first reflected from the Earth. Since the Earth appears near full phase from the Moon -- when the Moon appears as a slight crescent from the Earth -- earthshine is then near its brightest. Featured here in combined, consecutively-taken, HDR images taken earlier this month, a rising earthshine Moon was captured passing slowly near the planet Venus, the brightest spot near the image center. Just above Venus is the star Dschubba (catalogued as Delta Scorpii), while the red star on the far left is Antares.The celestial show is visible through scenic cloud decks.In the foreground are the lights...

APOD: 2021 October 17 - The Einstein Cross Gravitational Lens 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 October 17 The Einstein Cross Gravitational Lens Image Credit & License: J. Rhoads(Arizona State U.) et al.,WIYN,AURA,NOIRLab,NSF Explanation: Most galaxies have a single nucleus -- does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar. The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross. Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy. Tomorrow's picture: earthshine fireworks <| Archive| Submissions | Index| Search| Calendar| RSS| Education| About APOD| Discuss| > Authors & editors:...

APOD: 2021 October 16 - The Moona Lisa 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 October 16 The Moona Lisa Image Credit &Copyright:Gianni SarconeandMarcella Giulia Pace Explanation: Only natural colorsof the Moon in planet Earth'ssky appear in this creative visual presentation.Arrangedas pixelsin a framed image, the lunar disks were photographed at different times.Their varying hues are ultimately due to reflected sunlightaffected by changing atmospheric conditions and thealignmentgeometry of Moon, Earth, and Sun.Here, the darkest lunar disks are thecolors of earthshine.A description of earthshine, in terms of sunlight reflected by Earth'soceans illuminating the Moon's dark surface, was written over 500 yearsago by Leonardo da Vinci. But stand farther back from your monitor or just shift your gaze to the smallerversions of the image.You might also see one of da Vinci's most famousworks of art. Tonight:International Observe the Moon Night Tomorrow's picture: looking through gravity's lens<| 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 October 15 - NGC 289: Swirl in the Southern Sky 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 October 15 NGC 289: Swirl in the Southern Sky Image Credit &Copyright:Mike Selby Explanation: About 70 million light-years distant, gorgeous spiral galaxy NGC 289 islarger than ourown Milky Way.Seen nearly face-on, its bright core and colorful central disk give wayto remarkably faint, bluish spiral arms.The extensive armssweep well over 100 thousand light-years from the galaxy's center.At the lower right in this sharp,telescopic galaxy portraitthe main spiral arm seems toencounter a small, fuzzy ellipticalcompanion galaxy interacting with enormous NGC 289.Of course spiky stars are in the foreground of the scene.They lie within the Milky Way toward the southern constellationSculptor. Tomorrow's picture: Pixel 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 of:ASD atNASA /GSFC& Michigan Tech. U.

APOD: 2021 October 14 - NGC 7293: The Helix Nebula 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 October 14 NGC 7293: The Helix Nebula Image Credit &Copyright:Ignacio Diaz Bobillo Explanation: A mere seven hundred light years from Earth, toward the constellationAquarius,a sun-like star is dying.Its last few thousand years have produced theHelixNebula (NGC 7293), a well studied and nearby example of aPlanetaryNebula, typical of this final phase of stellar evolution. A total of 90 hours of exposure time have gone in to creatingthis expansive view of the nebula.Combining narrow band image data from emission lines of hydrogen atomsin red and oxygen atoms in blue-green hues,it shows remarkable details of theHelix's brighter inner region about 3light-years across.The white dot at the Helix's center is this Planetary Nebula's hot,central star.A simple looking nebula at first glance,the Helix is now understood to have a surprisinglycomplex geometry. 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 of:ASD atNASA /GSFC& Michigan...

APOD: 2021 October 13 - NGC 7822: Cosmic Question Mark 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 October 13 NGC 7822: Cosmic Question Mark Image Credit & Copyright: Yizhou Zhang Explanation: It may look like a huge cosmic question mark, but the big question really is how does the bright gas and dark dust tell this nebula's history of star formation. At the edge of a giantmolecular cloud toward the northernconstellation Cepheus, the glowing star forming region NGC 7822 lies about 3,000 light-years away.Within the nebula, bright edges and dark shapes stand out in thiscolorful and detailed skyscape.The 9-panel mosaic, taken over 28 nights with a small telescope in Texas,includes data from narrowband filters,mapping emission from atomic oxygen, hydrogen, and sulfur into blue,green, and red hues.The emission line and color combination has become well-known as theHubble palette.The atomic emission is powered by energetic radiation from the central hot stars.Their powerful winds and radiation sculpt and erodethe denser pillar shapes and clear out acharacteristic cavity light-years acrossthe center of the natal cloud.Stars could still be forming inside the pillars bygravitational collapse but as the...

APOD: 2021 October 12 - Fireball over Lake Louise 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 October 12 Fireball over Lake Louise Image Credit & Copyright: Hao Qin Explanation: What makes a meteor a fireball? First of all, everyone agrees that a fireball is an exceptionally bright meteor.Past that, the International Astronomical Union defines a fireball as a meteor brighter than apparent magnitude -4, which corresponds (roughly) to being brighter than any planet -- as well as bright enough to cast a human-noticeable shadow. Pictured, an astrophotographer taking a long-duration sky image captured by accident the brightest meteor he had ever seen. Clearly a fireball, the disintegrating space-rock created a trail so bright it turned night into day for about two seconds earlier this month. The fireball has been artificially dimmed in the featured image to bring up foreground Lake Louise in Alberta, Canada. Although fireballs are rare, many people have been lucky enough to see them. If you see a fireball, you can report it. If more than one person recorded an image, the fireball might be traceable back to the Solar...

APOD: 2021 October 11 - Juno Flyby of Ganymede and Jupiter 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. Juno Flyby of Ganymede and Jupiter Video Credit: Images: NASA,JPL-Caltech,SWRI,MSSS; Animation: Koji Kuramura, Gerald Eichstädt, Mike Stetson; Music: Vangelis Explanation: What would it be like to fly over the largest moon in the Solar System?In June, the robotic Juno spacecraft flew past Jupiter's huge moon Ganymede and took images that have been digitally constructed into a detailed flyby.As the featured video begins, Juno swoops over the two-toned surface of the 2,000-km wide moon, revealing an icy alien landscape filled with grooves and craters.The grooves are likely caused by shifting surface plates, while the craters are caused by violent impacts.Continuing on in its orbit, Juno then performed its 34th close pass over Jupiter's clouds.The digitally-constructed video shows numerous swirling clouds in the north, colorful planet-circling zones and bands across the middle -- featuring several white-oval clouds from the String of Pearls, and finally more swirling clouds in the south. Next September, Juno is scheduled to make a close pass over another of Jupiter's large moons: Europa. Tomorrow's picture: fireball...

APOD: 2021 October 10 - Full Moon Silhouettes 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. Full Moon Silhouettes Video Credit & Copyright: Mark Gee; Music: Tenderness (Dan Phillipson) Explanation: Have you ever watched the Moon rise?The slow rise of a nearly full moon over a clear horizon can be an impressive sight.One impressive moonrise was imaged in early 2013 over Mount VictoriaLookout in Wellington, New Zealand.With detailed planning, an industrious astrophotographer placed a camera about two kilometers away and pointed it across the lookout to where the Moon would surely soon be making its nightly debut.The featured single shot sequence is unedited and shown in real time -- it is not a time lapse.People on Mount Victoria Lookout can be seen in silhouette themselves admiring the dawn of Earth's largest satellite.Seeing a moonrise yourself is not difficult: it happens every day, although only half the time at night.Each day the Moon rises about fifty minutes later than the previous day, with a full moon always rising at sunset. This Saturday, October 16, is International Observe the Moon Night, where you observe a first-quarter Moon...

APOD: 2021 October 9 - 50 Light years to 51 Pegasi 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 October 9 50 Light-years to 51 Pegasi Image Credit &Copyright:Josselin Desmars Explanation: It's only 50 light-yearsto 51 Pegasi.That star's position is indicated in this snapshot fromAugust, taken on a hazy night with mostly brighter stars visible abovethe dome at Observatoire de Haute-Provence in France.Twenty-six years ago,in October of 1995, astronomersMichel Mayor and Didier Quelozannounced a profound discovery made at the observatory.Using a precise spectrograph they had detected a planet orbiting 51 Peg,the first known exoplanet orbiting a sun-like star.Mayor and Queloz had used the spectrograph to measure changes in thestar's radial velocity,a regular wobble caused by the gravitationaltug of the orbiting planet.Designated 51 Pegasi b,the planet was determined tohave a mass at least half of Jupiter's massand an orbital period of 4.2 days,making it much closer to its parent star than Mercury is to the Sun.Their discovery was quickly confirmed and Mayor and Quelozwere ultimately awarded theNobel Prize in physicsin 2019.Now recognized as the prototype for the class of exoplanetsfondly known ashot Jupiters,51 Pegasi b...

APOD: 2021 October 8 - The Double Cluster 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 October 8 The Double Cluster in Perseus Image Credit &Copyright:Jack Groves Explanation: This pretty starfield spans about three full moons (1.5 degrees)across the heroic northern constellation ofPerseus.It holds the famouspair of open star clusters,h and Chi Persei.Also cataloged asNGC 869 (top) and NGC 884,both clusters are about 7,000 light-years away andcontain stars much younger and hotter than the Sun. Separated by only a few hundred light-years, the clusters areboth 13 million years youngbased onthe ages oftheir individualstars,evidence that they were likely a product of the samestar-forming region.Always a rewardingsight in binoculars,the Double Cluster iseven visible to the unaided eye fromdark locations.But a shroud of guitar strings was used to producediffraction spikeson the colorful stars imaged in this vibrant telescopic view. Global Moon Party: Including APOD's Best Moon Images: Saturday, October 9 Tomorrow's picture: 50 light-years to planet Dimidium<| 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...

APOD: 2021 October 7 - NGC 6559: East of the Lagoon 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 October 7 NGC 6559: East of the Lagoon Image Credit &Copyright:Roberto Sartori Explanation: Slide your telescope just east of the Lagoon Nebula to find thisalluring field of viewin the rich starfields of the constellationSagittarius toward the central Milky Way.Of course the Lagoon nebula is also known as M8, the eighth objectlisted inCharles Messier'sfamous catalog of bright nebulae and star clusters.Close on the skybut slightly fainter than M8,this complex of nebulae was left out of Messier's list though.It contains obscuring dust, striking red emissionand blue reflection nebulae of star-forming regionNGC 6559 at right.Like M8, NGC 6559 is located about 5,000 light-years awayalong the edge of a large molecular cloud.At that distance,this telescopic frame nearly 3 full moons widewould span about 130 light-years. Global Moon Party: NASA's Night Sky Network: Saturday, October 9 Tomorrow's picture: when stars play guitars<| 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...

APOD: 2021 October 6 - M43: Streams of Orion 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 October 6 M43: Streams of Orion Image Credit & Copyright: Jari Saukkonen Explanation: Where do the dark streams of dust in the Orion Nebula originate?This part of the Orion Molecular Cloud Complex, M43, is the often imaged but rarely mentioned neighbor of the more famous M42.M42, seen in part to the upper right, includes many bright stars from the Trapezium star cluster.M43 is itself a star forming region that displays intricately-laced streams of dark dust -- although it is really composed mostly of glowing hydrogen gas.The entire Orion field is located about 1600 light years away. Opaque to visible light, the picturesque dark dust is created in the outer atmosphere of massive cool stars and expelled by strong outer winds of protons and electrons. Tomorrow's picture: open 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 of:ASD atNASA /GSFC& Michigan Tech. U.

APOD: 2021 October 5 - Sunrise at the South Pole 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 October 5 Sunrise at the South Pole Image Credit & Copyright: Martin Wolf (U. Wisconsin), IceCube Neutrino Obs.,NSF; ht: Alice Allen Explanation: Sunrise at the South Pole is different.Usually a welcome sight, it follows months of darkness -- and begins months of sunshine.At Earth's poles, it can take weeks for the Sun to rise, in contrast with hours at any mid-latitude location. Sunrise at a pole is caused by the tilt of the Earth as it orbits the Sun, not by the rotation of the Earth. Although at a pole, an airless Earth would first see first Sun at an equinox, the lensing effect of the Earth's atmosphere and the size of the solar disk causes the top of the Sun to appear about two-weeks early. Pictured two weeks ago, the Sun peeks above the horizon of a vast frozen landscape at Earth's South Pole. The true South Pole is just a few meters to the left of the communications tower.This polar sunrise capture was particularly...

APOD: 2021 October 4 - NGC 4676: When Mice Collide 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 October 4 NGC 4676: When Mice Collide Image Credit: NASA, ESA, Hubble; Processing & Copyright: William Ostling (The Astronomy Enthusiast) Explanation: These two mighty galaxies are pulling each other apart. Known as the "Mice" because they have such long tails, each spiral galaxy has likely already passed through the other.The longtails are created by the relative difference between gravitational pulls on the near and far parts of each galaxy. Because the distances are so large, the cosmic interaction takes place in slow motion -- over hundreds of millions of years. NGC 4676 lies about 300 million light-years away toward the constellation of Bernice's Hair (Coma Berenices) and are likely membersof the Coma Cluster of Galaxies. The featured picture was taken with the Hubble Space Telescope's Advanced Camera for Surveys in 2002.These galactic mice will probably collide again and again over the next billion years so that, instead of continuing to pull each other apart, they coalesce to form a single galaxy. Follow APOD in English on:...

APOD: 2021 October 3 - The Holographic Principle and a Teapot 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 October 3 The Holographic Principle and a Teapot Image Credit: Caltech Explanation: Sure, you can see the 2D rectangle of colors, but can you see deeper? Counting color patches in the featured image, you might estimate that the mostinformation that this 2D digital image can hold is about60 (horizontal) x 50(vertical) x 256 (possible colors) = 768,000 bits. However, the yet-unproven Holographic Principle states that, counter-intuitively, the information in a 2D panel can include all of the information in a 3D room that can be enclosed by the panel. The principle derives from the idea that thePlanck length, the length scale wherequantum mechanics begins to dominateclassical gravity, is one side of an areathat can hold only about one bit of information. The limit was first postulated by physicistGerard 't Hooft in 1993. It can arise from generalizations from seeminglydistant speculation that the information held by ablack hole is determined not by itsenclosed volume but by the surface area of itsevent horizon. The term "holographic" arises...

APOD: 2021 October 2 - A Light and Dusty Night 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 October 2 A Light and Dusty Night Image Credit &Copyright:Rodrigo Guerra Explanation: Posing as a brilliant evening star,Venus lies near the western horizonin this southern hemisphere, early spring, night skyscape.To create the composite view exposures tracking the skyand fixed for the foreground were taken onSeptember 25 from Cascavel in southern Brazil.In view after sunset, Venus appears immersed in a cone of zodiacal light,sunlight scattered from dust along theSolar System's ecliptic plane.In fact from either hemisphere of planet Earth,zodiacal light is most visibleafter sunset near a spring equinox,(or before sunrise near an autumn equinox)when its luminous arc lies at steep angles to the horizon.Extending above the sunset on this night, the zodiacal lightreaches toward rich starfields and immense interstellar dust cloudsin the bulge of the central Milky Way.Follow along the Milky Way from the central bulge back toward the horizonand you'll spot the closest star system to the Sun,Alpha Centauri, a mere 4.37 light-years away. Tomorrow's picture: holographic tea time<| Archive| Submissions | Index| Search| Calendar| RSS|...