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Astronomy Picture of the Day (General/Chat)

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  • Astronomy Picture of the Day -- Aurora Australis

    07/04/2015 5:20:45 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | July 04, 2015 | (see photo credit)
    Explanation: Not fireworks, these intense shimmering lights still danced across Earth's night skies late last month, seen here above the planet's geographic south pole. The stunning auroral displays were triggered as a coronal mass ejection blasted from the Sun days earlier impacted the magnetosphere, beginning a widespread geomagnetic storm. The six fisheye panels were recorded with digital camera and battery in a heated box to guard against -90 degree F ambient temperatures of the long winter night. Around the horizon are south pole astronomical observatories, while beyond the Aurora Australis stretch the stars of the southern Milky Way.
  • Astronomy Picture of the Day -- Venus and Jupiter are Far

    07/03/2015 7:40:22 AM PDT · by SunkenCiv · 16 replies
    NASA ^ | July 03, 2015 | (see photo credit)
    Explanation: On June 30 Venus and Jupiter were actually far apart, but both appeared close in western skies at dusk. Near the culmination of this year's gorgeous conjunction, the two bright evening planets are captured in the same telescopic field of view in this sharp digital stack of images taken after sunset from Poznań in west-central Poland. In fact, banded gas giant Jupiter was about 910 million kilometers from Poland. That's over 11 times farther than crescent Venus, only 78 million kilometers distant at the time. But since the diameter of giant planet Jupiter is over 11 times larger than...
  • Astronomy Picture of the Day -- Venus and Jupiter are Close

    07/02/2015 11:17:19 AM PDT · by SunkenCiv · 18 replies
    NASA ^ | July 02, 2015 | (see photo credit)
    Explanation: On June 30, Venus and Jupiter were close in western skies at dusk. Near the culmination of this year's gorgeous conjunction, the two bright evening planets are captured in the same telescopic field of view in this image taken after sunset from Bejing, China. As the two bright planets set together in the west, a nearly Full Moon rose above the horizon to the south and east. Imaged that night with the same telescope and camera, the rising Moon from the opposite part of the sky is compared with the planetary conjunction for scale in the digitally composited image....
  • Astronomy Picture of the Day -- Venus, Jupiter, and Noctilucent Clouds

    07/01/2015 3:18:08 PM PDT · by SunkenCiv · 10 replies
    NASA ^ | July 01, 2015 | (see photo credit)
    Explanation: Have you seen the passing planets yet? Today the planets Jupiter and Venus pass within half a degree of each other as seen from Earth. This conjunction, visible all over the world, is quite easy to see -- just look to the west shortly after sunset. The brightest objects visible above the horizon will be Venus and Jupiter, with Venus being the brighter of the two. Featured above, the closing planets were captured two nights ago in a sunset sky graced also by high-level noctilucent clouds. In the foreground, the astrophotographer's sister takes in the vista from a bank...
  • Astronomy Picture of the Day -- An Unusual Mountain on Asteroid Ceres

    06/29/2015 9:49:58 PM PDT · by SunkenCiv · 18 replies
    NASA ^ | June 30, 2015 | (see photo credit)
    Explanation: What created this large mountain on asteroid Ceres? No one is yet sure. As if in anticipation of today being Asteroid Day on Earth, the robotic spacecraft Dawn in orbit around Ceres took the best yet image of an unusually tall mountain on the Asteroid Belt's largest asteroid. Visible at the top of the featured image, the exceptional mountain rises about five kilometers up from an area that otherwise appears pretty level. The image was taken about two weeks ago from about 4,400 kilometers away. Although origin hypotheses for the mountain include volcanism, impacts, and plate tectonics, clear evidence...
  • Astronomy Picture of the Day -- Sunspot Group AR 2339 Crosses the Sun

    06/29/2015 7:18:10 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | June 29, 2015 | (see photo credit)
    Explanation: How do sunspots evolve? Large dark sunspots -- and the active regions that contain them -- may last for weeks, but all during that time they are constantly changing. Such variations were particularly apparent a few weeks ago as the active region AR 2339 came around the limb of the Sun and was tracked for the next 12 days by NASA's Solar Dynamic Observatory. In the featured time lapse video, some sunspots drift apart, while others merge. All the while, the dark central umbral regions shift internally and their surrounding lighter penumbras shimmer and wave. The surrounding Sun appears...
  • Astronomy Picture of the Day -- All the Colors of the Sun

    06/27/2015 9:16:14 PM PDT · by SunkenCiv · 20 replies
    NASA ^ | June 28, 2015 | (see photo credit)
    Explanation: It is still not known why the Sun's light is missing some colors. Here are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device. The spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our white-appearing Sun emits light of nearly every color, it does indeed appear brightest in yellow-green light. The dark patches in the above spectrum arise from gas at or above the Sun's surface absorbing sunlight emitted below. Since different types of gas absorb different colors of light, it is possible to determine...
  • Astronomy Picture of the Day -- Stars of a Summer's Triangle

    06/27/2015 3:42:59 PM PDT · by SunkenCiv · 13 replies
    NASA ^ | June 27, 2015 | (see photo credit)
    Explanation: Rising at the start of a northern summer's night, these three bright stars form the familiar asterism known as the Summer Triangle. Altair, Deneb, and Vega are the alpha stars of their respective constellations, Aquila, Cygnus, and Lyra, nestled near the Milky Way. Close in apparent brightness the three do look similar in these telescopic portraits, but all have their own stellar stories. Their similar appearance hides the fact that the Summer Triangle stars actually span a large range in intrinsic luminosity and distance. A main sequence dwarf star, Altair is some 10 times brighter than the Sun and...
  • Astronomy Picture of the Day -- Planet Aurora

    06/26/2015 1:21:43 PM PDT · by SunkenCiv · 5 replies
    NASA ^ | June 26, 2015 | (see photo credit)
    Explanation: What bizarre alien planet is this ? It's planet Earth of course, seen through the shimmering glow of aurorae from the International Space Station. About 400 kilometers (250 miles) above, the orbiting station is itself within the upper realm of the auroral displays, also watched from the planet's surface on June 23rd. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. The eerie greenish glow of molecular oxygen dominates this view. But higher, just above the space station's horizon, is a rarer red band of aurora from atomic oxygen. The...
  • Astronomy Picture of the Day -- Star Trails above Table Mountain

    06/26/2015 1:21:40 PM PDT · by SunkenCiv · 8 replies
    NASA ^ | June 25, 2015 | (see photo credit)
    Explanation: Stars trail above and urban lights sprawl below in this moonlit nightscape from Cape Town, South Africa, planet Earth. The looming form of Table Mountain almost seems to hold terrestrial lights at bay while the stars circle the planet's South Celestial Pole. This modern perspective on the natural night sky was captured in June 2014, the scene composed of over nine hundred, stacked 30 second exposures. The stunning result was chosen as the winner in the Against the Lights category, a selection from over 800 entries in The World at Night's 2015 International Earth and Sky Photo Contest.
  • Astronomy Picture of the Day -- Triple Conjunction Over Galician National Park

    06/24/2015 4:04:07 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | June 24, 2015 | (see photo credit)
    Explanation: What are those bright objects hovering over the horizon? Planets -- and the Moon. First out, the horizon featured is a shoreline of the Atlantic Ocean that occurs at the Galicia National Park in northern Spain. Next furthest out, on the left, is the Moon. Easily the brightest object on the night sky, the Moon here was in only a crescent phase. The next furthest out, on the right, is the planet Venus, while planet Jupiter is seen at the top of the triangle. The long exposure from our rapidly rotating Earth made all of celestial objects -- including...
  • Astronomy Picture of the Day -- Sharpless 308: Star Bubble

    06/23/2015 4:14:40 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | June 23, 2015 | (see photo credit)
    Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 2-308 it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive...
  • Astronomy Picture of the Day -- New Horizons [Pluto probe]

    06/21/2015 10:04:05 PM PDT · by SunkenCiv · 3 replies
    NASA ^ | June 22, 2015 | (see photo credit)
    Explanation: In three weeks, the robotic New Horizons spacecraft will reach Pluto. As the featured video makes clear, though, humanity has been on an unprecedented epoch of robotic exploration of our Solar System's planets for the past half century. The video highlights artistic illustrations of Mariner 2 flying by Venus in 1962, Mariner 4 flying past Mars in 1965, Pioneer 10 flying past Jupiter in 1973, Mariner 10 flying past Mercury in 1974, Pioneer 11 flying past Saturn in 1979, and Voyager 2 flying past Uranus in 1986 and then Neptune in 1989. Next is a hypothetical sequence depicting New...
  • Astronomy Picture of the Day -- Rings and Seasons of Saturn

    06/21/2015 7:10:57 AM PDT · by SunkenCiv · 15 replies
    NASA ^ | June 21, 2015 | (see photo credit)
    Explanation: On Saturn, the rings tell you the season. On Earth, today marks a solstice, the time when the Earth's spin axis tilts directly toward the Sun. On Earth's northern hemisphere, today is the Summer Solstice, the day of maximum daylight. Since Saturn's grand rings orbit along the planet's equator, these rings appear most prominent -- from the direction of the Sun -- when the Saturn's spin axis points toward the Sun. Conversely, when Saturn's spin axis points to the side, an equinox occurs and the edge-on rings are hard to see. In the featured montage, images of Saturn over...
  • Astronomy Picture of the Day -- Hubble's Messier 5 [whoa!]

    06/19/2015 11:33:10 PM PDT · by SunkenCiv · 27 replies
    NASA ^ | June 20, 2015 | (see photo credit)
    Explanation: "Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ..." begins the description of the 5th entry in 18th century astronomer Charles Messier's famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one...
  • Astronomy Picture of the Day -- LightSail A

    06/19/2015 5:31:30 PM PDT · by SunkenCiv · 3 replies
    NASA ^ | June 19, 2015 | (see photo credit)
    Explanation: Hitching a ride to low Earth orbit, LightSail A accomplished a challenging test mission, unfurling its 32 square meter mylar solar sail on June 7. This dramatic image from one of the bread loaf sized spacecraft's fisheye cameras captures the deployed sail glinting in sunlight. Sail out and visible to Earthbound observers before its final orbit, LightSail A reentered the atmosphere last weekend. Its succesful technology demonstration paves the way for the LightSail B spacecraft, scheduled for launch in April 2016. Once considered the stuff of science fiction, sailing through space was suggested 400 years ago by astronomer Johannes...
  • Astronomy Picture of the Day -- M64: The Black Eye Galaxy

    06/18/2015 4:26:59 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | June 18, 2015 | (see photo credit)
    Explanation: This big, bright, beautiful spiral galaxy is Messier 64, often called the Black Eye Galaxy or the Sleeping Beauty Galaxy for its heavy-lidded appearance in telescopic views. M64 is about 17 million light-years distant in the otherwise well-groomed northern constellation Coma Berenices. In fact, the Red Eye Galaxy might also be an appropriate moniker in this colorful composition. The enormous dust clouds obscuring the near-side of M64's central region are laced with the telltale reddish glow of hydrogen associated with star forming regions. But they are not this galaxy's only peculiar feature. Observations show that M64 is actually composed...
  • Astronomy Picture of the Day -- M45: The Pleiades Star Cluster

    06/17/2015 11:11:55 AM PDT · by SunkenCiv · 23 replies
    NASA ^ | June 17, 2015 | (see photo credit)
    Explanation: Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as dusty as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-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 took over 12 hours and covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45, the...
  • Astronomy Picture of the Day -- APOD is 20 Years Old Today

    06/16/2015 9:25:10 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | June 16, 2015 | (see photo credit)
    Explanation: Welcome to the vicennial year of the Astronomy Picture of the Day! Perhaps a source of web consistency for some, APOD is still here. As during each of the 20 years of selecting images, writing text, and editing the APOD web pages, the occasionally industrious Robert Nemiroff (left) and frequently persistent Jerry Bonnell (right) are pictured above plotting to highlight yet another unsuspecting image of our cosmos. Although the featured image may appear similar to the whimsical Vermeer composite that ran on APOD's fifth anniversary, a perceptive eye might catch that it has been digitally re-pixelated using many of...
  • Astronomy Picture of the Day -- A Colorful Lunar Corona

    06/15/2015 4:21:04 PM PDT · by SunkenCiv · 10 replies
    NASA ^ | June 15, 2015 | (see photo credit)
    Explanation: What are those colorful rings around the Moon? A corona. Rings like this will sometimes appear when the Moon is seen through thin clouds. The effect is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths, each color diffracts differently. Lunar Coronae are one of the few quantum mechanical color effects that can be easily seen with the unaided eye. The featured lunar corona was captured around a Strawberry Moon on June 2 from La Plata, Argentina. Similar coronae that form...
  • Astronomy Picture of the Day -- M101: The Pinwheel Galaxy

    06/15/2015 4:20:11 PM PDT · by SunkenCiv · 5 replies
    NASA ^ | June 14, 2015 | (see photo credit)
    Explanation: Why do many galaxies appear as spirals? A striking example is M101, shown above, whose relatively close distance of about 27 million light years allows it to be studied in some detail. Observational 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...
  • Astronomy Picture of the Day -- 1000 Sols

    06/15/2015 4:18:08 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | June 13, 2015 | (see photo credit)
    Explanation: Shortly before Mars' June 2015 conjunction, the Curiosity Rover celebrated 1000 sols on the red planet. After its August 5, 2012 landing, Curiosity's 1000th sol or martian day on the surface corresponded to planet Earth's calendar date May 31, 2015. Because the line-of-sight to Mars is close to the Sun near the conjunction, radio communications are affected and the six-wheeled, car-sized robotic rover cautiously remains parked at this spot for now. The view looks back toward the stomping grounds for Curiosity's nearly 10.6 kilometer trek so far, with the hazy rim of Gale Crater in the distance. The mosaicked...
  • Astronomy Picture of the Day -- The Medusa Nebula

    06/12/2015 4:11:16 AM PDT · by SunkenCiv · 8 replies
    NASA ^ | June 12, 2015 | (see photo credit)
    Explanation: Braided, serpentine filaments of glowing gas suggest this nebula's popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old planetary nebula some 1,500 light-years away along the southern border of the constellation Gemini. Like its mythological namesake, the nebula is associated with a dramatic transformation. The planetary nebula phase represents a final stage in the evolution of low mass stars like the sun, as they transform themselves from red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet radiation from the hot star powers the nebular glow....
  • Astronomy Picture of the Day -- The Light, the Dark, and the Dusty

    06/11/2015 4:01:59 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | June 11, 2015 | (see photo credit)
    Explanation: This colorful skyscape spans about three full moons (1.5 degrees) across nebula rich starfields along the plane of our Milky Way Galaxy in the royal northern constellation Cepheus. Near the edge of the region's massive molecular cloud some 2,400 light-years away, bright reddish emission region Sharpless (Sh) 155 lies at the upper left, also known as the Cave Nebula. About 10 light-years across the cosmic cave's bright rims of gas are ionized by ultraviolet light from hot young stars. Dusty blue reflection nebulae also abound on the interstellar canvas cut by dense obscuring clouds of dust. The long core...
  • Astronomy Picture of the Day -- Fly Over Dwarf Planet Ceres

    06/10/2015 3:55:24 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | June 10, 2015 | (see photo credit)
    Explanation: What would it look like to fly over dwarf planet Ceres? Animators from the German Aerospace Center recently took actual images and height data from NASA's robotic Dawn mission -- currently visiting Ceres -- to generate several fascinating virtual sequences. The featured video begins with a mock orbit around the 950-km wide space rock, with the crater featuring two of the enigmatic white spots soon rotating into view. The next sequences take the viewer around the Ceres' north and south poles, and then over a limb of the dark world highlighting its heavily cratered surface. Here, terrain height on...
  • Astronomy Picture of the Day -- Galaxy NGC 7714 After Collision

    06/09/2015 9:36:36 AM PDT · by SunkenCiv · 8 replies
    NASA ^ | June 09, 2015 | (see photo credit)
    Explanation: Is this galaxy jumping through a giant ring of stars? Probably not. Although the precise dynamics behind the featured image is yet unclear, what is clear is that the pictured galaxy, NGC 7714, has been stretched and distorted by a recent collision with a neighboring galaxy. This smaller neighbor, NGC 7715, situated off to the left of the featured frame, is thought to have charged right through NGC 7714. Observations indicate that the golden ring pictured is composed of millions of older Sun-like stars that are likely co-moving with the interior bluer stars. In contrast, the bright center of...
  • Astronomy Picture of the Day -- The Milky Way over the Temple of Poseidon

    06/08/2015 6:54:13 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | June 08, 2015 | (see photo credit)
    Explanation: What's that glowing in the distance? Although it may look like a lighthouse, the rays of light near the horizon actually emanate from the Temple of Poseidon at Cape Sounion, Greece. Some temple lights are even reflected in the Aegean Sea in the foreground. Although meant to be a monument to the sea, in this image, the temple's lights seem to be pointing out locations on the sky. For example, the wide ray toward the right fortuitously points toward the Lagoon Nebula in the central band of our Milky Way, which runs diagonally down the image from the upper...
  • Astronomy Picture of the Day -- NGC 3132: The Eight Burst Nebula

    06/06/2015 10:50:20 PM PDT · by SunkenCiv · 3 replies
    NASA ^ | June 07, 2015 | (see photo credit)
    Explanation: It's the dim star, not the bright one, near the center of NGC 3132 that created this odd but beautiful planetary nebula. Nicknamed the Eight-Burst Nebula and the Southern Ring Nebula, the glowing gas originated in the outer layers of a star like our Sun. In this representative color picture, the hot blue pool of light seen surrounding this binary system is energized by the hot surface of the faint star. Although photographed to explore unusual symmetries, it's the asymmetries that help make this planetary nebula so intriguing. Neither the unusual shape of the surrounding cooler shell nor the...
  • Astronomy Picture of the Day -- Into the Void

    06/06/2015 4:37:43 AM PDT · by SunkenCiv · 13 replies
    NASA ^ | June 06, 2015 | (see photo credit)
    Explanation: Fifty years ago, on June 3, 1965, Edward White stepped out of the orbiting Gemini 4 spacecraft to become the first US astronaut to walk in space. White is captured in this photo taken by mission commander James McDivit from inside the capsule as White's spacewalk began over the Pacific Ocean on Gemini 4's third orbit. Planet Earth, spacecraft, and tether are reflected in White's gold tinted helmet visor. A gas powered manuevering gun is held in his right hand. Though the gun ran out of gas after only 3 minutes, he continued to manuever by twisting his body...
  • Astronomy Picture of the Day -- Green Flash at Moonrise

    06/05/2015 3:01:47 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | June 05, 2015 | (see photo credit)
    Explanation: Follow a sunset on a clear day against a distant horizon and you might glimpse a green flash just as the Sun disappears, the sunlight briefly refracted over a long sight-line through atmospheric layers. You can spot a green flash at sunrise too. Pinpointing the exact place and time to see the rising Sun peeking above the horizon is a little more difficult though, and it can be harder still to catch a green flash from the fainter rising Moon. But well-planned snapshots did record a green flash at the Full Moon's upper edge on June 2nd, from the...
  • Astronomy Picture of the Day -- NGC 2419 - Intergalactic Wanderer

    06/04/2015 12:17:37 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | June 04, 2015 | (see photo credit)
    Explanation: Three objects stand out in this thoughtful telescopic image, a view toward the mostly stealthy constellation Lynx. The two brightest (the spiky ones) are nearby stars. The third is the remote globular star cluster NGC 2419, at distance of nearly 300,000 light-years. NGC 2419 is sometimes called "the Intergalactic Wanderer", an appropriate title considering that the distance to the Milky Way's satellite galaxy, the Large Magellanic Cloud, is only about 160,000 light-years. Roughly similar to other large globular star clusters like Omega Centauri, NGC 2419 is itself intrinsically bright, but appears faint because it is so far away. NGC...
  • Astronomy Picture of the Day -- Flyby Image of Saturn's Sponge Moon Hyperion

    06/03/2015 6:22:25 AM PDT · by SunkenCiv · 10 replies
    NASA ^ | June 03, 2015 | (see photo credit)
    Explanation: Why does this moon look like a sponge? To better investigate, NASA and ESA sent the Saturn-orbiting robotic spacecraft Cassini zooming past Saturn's moon Hyperion, once again, earlier this week. One of the images beamed back to Earth is featured above, raw and unprocessed. Visible, as expected, are many unusually shaped craters with an unusual dark material at the bottom. Although Hyperion spans about 250 kilometers, its small gravitational tug on Cassini indicates that it is mostly empty space and so has very low surface gravity. Therefore, the odd shapes of many of Hyperion's craters are thought to result...
  • Astronomy Picture of the Day -- Polaris and Comet Lovejoy

    06/02/2015 10:34:39 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | June 02, 2015 | (see photo credit)
    Explanation: One of these two bright sky objects is moving. On the right is the famous star Polaris. Although only the 45th brightest star in the sky, Polaris is famous for appearing stationary. Once you find it, it will always appear in the same direction -- all night and all day -- for the rest of your life. This is because the northern spin pole of the Earth -- called the North Celestial Pole -- points near Polaris. On the left, about ten million times closer, is Comet Lovejoy, which noticeably changes its sky position by the hour. The featured...
  • Full Strawberry Moon on June 2, 2015

    06/02/2015 5:45:04 AM PDT · by onyx · 21 replies
    EarthSky ^ | June 2, 2015 | EarthSky
    Tonight – June 2, 2015 – watch for the full moon to group up with the planet Saturn and star Antares in the eastern sky at dusk and nightfall. As our Earth turns underneath the heavens tonight, look for this full moon, Saturn and Antares to move westward across the nighttime sky. The celestial threesome will climb highest up tonight around midnight, and will sit low in the west at dawn June 3. In North America, we commonly call the June full moon the Strawberry Moon. This year’s Strawberry Moon turns precisely full on June 2, 2015 at 16:19...
  • Astronomy Picture of the Day -- Pulsating Aurora over Iceland

    05/31/2015 10:01:57 PM PDT · by SunkenCiv · 5 replies
    NASA ^ | June 01, 2015 | (see photo credit)
    Explanation: Why do some auroras pulsate? No one is sure. Although this unusual behavior has been known for a long time, the cause remains an active topic of research. Featured here is a dramatic video that captured some impressive pulsating auroras in mid-March over Svínafellsjökull Glacier in Iceland. The 48-second video is shown is not time-lapse. The real-time pulsations are exemplified by sequences where the astrophotographer is visible moving about in the foreground. A close inspection of the enigmatic flickering sky colors reveals that some structures appear to repeat, while others do not. The quick rapidity of the pulsations seen...
  • Astronomy Picture of the Day -- Supernova 1994D and the Unexpected Universe

    05/31/2015 8:55:02 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | May 31, 2015 | (see photo credit)
    Explanation: Long ago, far away, a star exploded. Supernova 1994D, visible as the bright spot on the lower left, occurred in the outskirts of disk galaxy NGC 4526. Supernova 1994D was not of interest for how different it was, but rather for how similar it was to other supernovae. In fact, the light emitted during the weeks after its explosion caused it to be given the familiar designation of a Type Ia supernova. If all Type 1a supernovae have the same intrinsic brightness, then the dimmer a supernova appears, the farther away it must be. By calibrating a precise brightness-distance...
  • Astronomy Picture of the Day -- Messier Craters in Stereo

    05/30/2015 3:06:55 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | May 30, 2015 | (see photo credit)
    Explanation: Many bright nebulae and star clusters in planet Earth's sky are associated with the name of astronomer Charles Messier, from his famous 18th century catalog. His name is also given to these two large and remarkable craters on the Moon. Standouts in the dark, smooth lunar Sea of Fertility or Mare Fecunditatis, Messier (left) and Messier A have dimensions of 15 by 8 and 16 by 11 kilometers respectively. Their elongated shapes are explained by an extremely shallow-angle trajectory followed by the impactor, moving left to right, that gouged out the craters. The shallow impact also resulted in two...
  • Astronomy Picture of the Day -- Saturn at Opposition

    05/29/2015 2:15:34 PM PDT · by SunkenCiv · 9 replies
    NASA ^ | May 29, 2015 | (see photo credit)
    Explanation: Telescopic observers on Earth have been treated to spectacular views of Saturn lately as the ringed planet reached its 2015 opposition on May 23 at 0200 UT. Of course opposition means opposite the Sun in Earth's sky. So near opposition Saturn is up all night, at its closest and brightest for the year. These sharp images taken within hours of the Sun-Earth-Saturn alignment also show the strong brightening of Saturn's rings known as the opposition surge or the Seeliger Effect. Directly illuminated, the ring's icy particles cast no shadows and strongly backscatter sunlight toward planet Earth, creating the dramatic...
  • Astronomy Picture of the Day -- Nearby Spiral Galaxy NGC 4945

    05/28/2015 4:59:41 AM PDT · by SunkenCiv · 7 replies
    NASA ^ | May 28, 2015 | (see photo credit)
    Explanation: Large spiral galaxy NGC 4945 is seen edge-on near the center of this cosmic galaxy portrait. In fact, NGC 4945 is almost the size of our own Milky Way Galaxy. Its own dusty disk, young blue star clusters, and pink star forming regions standout in the sharp, colorful telescopic image. About 13 million light-years distant toward the expansive southern constellation Centaurus, NGC 4945 is only about six times farther away than Andromeda, the nearest large spiral galaxy to the Milky Way. Though the galaxy's central region is largely hidden from view for optical telescopes, X-ray and infrared observations indicate...
  • Astronomy Picture of the Day -- Approaching Pluto

    05/27/2015 1:32:31 PM PDT · by SunkenCiv · 10 replies
    NASA ^ | May 27, 2015 | (see photo credit)
    Explanation: Here comes Pluto. NASA's robotic New Horizons spacecraft is now beyond the orbit of Neptune and closing fast on the Solar System's most famous unexplored world. The featured time lapse video shows Pluto and Pluto's largest moon, Charon, orbiting their common center of mass in 13 frames taken from April 12 to April 18. Although blurry, images in the video now rival even the best images of Pluto yet taken from Earth. New Horizons remains on schedule to zoom past the distant dwarf planet on July 14.
  • Astronomy Picture of the Day -- Starburst Galaxy M94

    05/26/2015 7:03:13 AM PDT · by SunkenCiv · 10 replies
    NASA ^ | May 26, 2015 | (see photo credit)
    Explanation: What could cause the center of M94 to be so bright? Spiral galaxy M94 has a ring of newly formed stars surrounding its nucleus, giving it not only an unusual appearance but also a strong interior glow. A leading progenitor hypothesis holds that an elongated knot of stars known as a bar rotates in M94 and has generated a burst of star formation in the inner ring. Recent observations have revealed the outer, fainter ring is not closed and relatively complex. M94, pictured here spans about 30,000 light years, lies about 15 million light years away, and can be...
  • Astronomy Picture of the Day -- The Galaxy Tree

    05/25/2015 12:23:13 PM PDT · by SunkenCiv · 2 replies
    NASA ^ | May 25, 2015 | (see photo credit)
    Explanation: First came the trees. In the town of Salamanca, Spain, the photographer noticed how distinctive a grove of oak trees looked after being pruned. Next came the galaxy. The photographer stayed up until 2 am, waiting until the Milky Way Galaxy rose above the level of a majestic looking oak. From this carefully chosen perspective, dust lanes in the galaxy appear to be natural continuations to branches of the tree. Last came the light. A flashlight was used on the far side of the tree to project a silhouette. By coincidence, other trees also appeared as similar silhouettes across...
  • Astronomy Picture of the Day -- Space Shuttle Rising

    05/25/2015 12:23:10 PM PDT · by SunkenCiv · 11 replies
    NASA ^ | May 24, 2015 | (see photo credit)
    Explanation: What's that rising from the clouds? The space shuttle. Sometimes, if you looked out the window of an airplane at just the right place and time, you could have seen something very unusual -- a space shuttle launching to orbit. Images of the rising shuttle and its plume became widely circulated over the web shortly after Endeavour's final launch in 2011 May. The above image was taken from a shuttle training aircraft by NASA and is not copyrighted. Taken well above the clouds, the image can be matched with similar images of the same shuttle plume taken below the...
  • Astronomy Picture of the Day -- NGC 7822 in Cepheus

    05/25/2015 12:23:07 PM PDT · by SunkenCiv · 2 replies
    NASA ^ | May 23, 2015 | (see photo credit)
    Explanation: Hot, young stars and cosmic pillars of gas and dust seem to crowd into NGC 7822. At the edge of a giant molecular cloud toward the northern constellation Cepheus, the glowing star forming region lies about 3,000 light-years away. Within the nebula, bright edges and dark shapes are highlighted in this colorful skyscape. The image includes data from narrowband filters, mapping emission from atomic oxygen, hydrogen, and sulfur into blue, green, and red hues. The atomic emission is powered by energetic radiation from the hot stars, whose powerful winds and radiation also sculpt and erode the denser pillar shapes....
  • Astronomy Picture of the Day -- A Dark and Dusty Sky

    05/22/2015 4:25:13 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | May 22, 2015 | (see photo credit)
    Explanation: In the dusty sky toward the constellation Taurus and the Orion Arm of our Milky Way Galaxy, this broad mosaic follows dark and faint reflection nebulae along the region's fertile molecular cloud. The six degree wide field of view starts with long dark nebula LDN 1495 stretching from the lower left, and extends beyond the (upside down) bird-like visage of the Baby Eagle Nebula, LBN 777, at lower right. Small bluish reflection nebulae surround scattered fainter Taurus stars, sights often skipped over in favor of the constellation's better known, brighter celestial spectacles. Associated with the young, variable star RY...
  • Astronomy Picture of the Day -- NGC 6240: Merging Galaxies

    05/21/2015 3:55:01 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | May 21, 2015 | (see photo credit)
    Explanation: NGC 6240 offers a rare, nearby glimpse of a cosmic catastrophe in its final throes. The titanic galaxy-galaxy collision takes place a mere 400 million light-years away in the constellation Ophiuchus. The merging galaxies spew distorted tidal tails of stars, gas, and dust and undergo fast and furious bursts of star formation. The two supermassive black holes in the original galactic cores will also coalesce into a single, even more massive black hole and soon, only one large galaxy will remain. This dramatic image of the scene is a composite of narrowband and near-infrared to visible broadband data from...
  • Astronomy Picture of the Day -- A Cliff Looming on Comet 67P

    05/20/2015 4:46:01 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | May 20, 2015 | (see photo credit)
    Explanation: What 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...
  • Astronomy Picture of the Day -- Globular Star Cluster 47 Tucanae

    05/19/2015 2:30:13 PM PDT · by SunkenCiv · 12 replies
    NASA ^ | May 19, 2015 | (see photo credit)
    Explanation: Globular star cluster 47 Tucanae is a jewel box of the southern sky. Also known as NGC 104, it roams the halo of our Milky Way Galaxy along with over 150 other globular star clusters. The second brightest globular cluster (after Omega Centauri) as seen from planet Earth, 47 Tuc lies about 17,000 light-years away and can be spotted naked-eye near the Small Magellanic Cloud in the constellation of the Toucan. The dense cluster is made up of hundreds of thousands of stars in a volume only about 120 light-years across. Recent observations have shown that 47 Tuc's white...
  • Astronomy Picture of the Day -- Auroras and Star Trails over Iceland

    05/18/2015 9:57:36 AM PDT · by SunkenCiv · 19 replies
    NASA ^ | May 18, 2015 | (see photo credit)
    Explanation: It was one of the quietest nights of aurora in weeks. Even so, in northern- Iceland during last November, faint auroras lit up the sky every clear night. The featured 360-degree panorama is the digital fusion of four wide-angle cameras each simultaneously taking 101 shots over 42 minutes. In the foreground is serene Lake Myvatn dotted with picturesque rock formations left over from ancient lava flows. Low green auroras sweep across the sky above showing impressive complexity near the horizon. Stars far in the distance appear to show unusual trails -- as the Earth turned -- because early exposures...
  • Astronomy Picture of the Day -- NGC 2440: Pearl of a New White Dwarf

    05/17/2015 11:50:08 AM PDT · by SunkenCiv · 15 replies
    NASA ^ | May 17, 2015 | (see photo credit)
    Explanation: Like a pearl, a white dwarf star shines best after being freed from its shell. In this analogy, however, the Sun would be a mollusk and its discarded hull would shine prettiest of all! In the above shell of gas and dust, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The glowing stellar pearl can be seen as the bright dot near the image center. The portion of NGC 2440 shown spans about one light year. The center of our Sun will eventually become a white dwarf, but not for another five...