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Explanation: What caused this outburst of V838 Mon? For reasons unknown, star V838 Mon suddenly became one of the brightest stars in the entire Milky Way Galaxy. Then, just a few months later, it faded. A stellar flash like this has never been seen before -- supernovas and novas expel a tremendous amount of matter out into space. Although the V838 Mon flash appeared to expel some material into space, what is seen in the above eight-frame movie, interpolated for smoothness, is actually an outwardly moving light echo of the flash. The actual time-span of the above movie is from...

Explanation: The first APOD appeared 19 years ago today. To help celebrate, APOD brings you today an all-sky heatmap of (nearly) 19 years of APOD entries. The brighter a region appears on the above heatmap, the more APODs that occur in that region. Clicking anywhere on the map will bring up a link to all APODs, if any, that appear nearby. We at APOD again thank our readers, NASA, astrophotographers, volunteers who translate APOD daily into over 20 languages, volunteers who run APOD's over 20 mirror sites, volunteers who answer questions and administer APOD's main discussion board, and volunteers who...

Explanation: Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group of Galaxies. The Local Group falls toward the Virgo Cluster of Galaxies. But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background radiation (CMBR). In the above all-sky map from the COBE satellite, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and...

Explanation: Bright stars of Sagittarius and the center of our Milky Way Galaxy lie just off the wing of a Boeing 747 in this astronomical travel photo. The stratospheric scene was captured earlier this month during a flight from New York to London, 11,0000 meters above the Atlantic Ocean. Of course the sky was clear and dark at that altitude, ideal conditions for astronomical imaging. But there were challenges to overcome while looking out a passenger window of the aircraft moving at nearly 1,000 kilometers per hour (600 mph). Over 90 exposures of 30 seconds or less were attempted with...

Explanation: June's Full Moon (full phase on June 13, 0411 UT) is traditionally known as the Strawberry Moon or Rose Moon. Of course those names might also describe the appearance of this Full Moon, rising last month over the small Swedish village of Marieby. The Moon looks large in the image because the scene was captured with a long focal length lens from a place about 8 kilometers from the foreground houses. But just by eye a Full Moon rising, even on Friday the 13th, will appear to loom impossibly large near the horizon. That effect has long been recognized...

Explanation: The Tarantula Nebula is more than 1,000 light-years in diameter, a giant star forming region within our neighboring galaxy the Large Magellanic Cloud (LMC). That cosmic arachnid lies toward the upper left in this deep and colorful telescopic view made through broad-band and narrow-band filters. The image spans nearly 2 degrees (4 full moons) on the sky and covers a part of the LMC over 8,000 light-years across. Within the Tarantula (NGC 2070), intense radiation, stellar winds and supernova shocks from the central young cluster of massive stars, cataloged as R136, energize the nebular glow and shape the spidery...

Explanation: No, radio dishes cannot broadcast galaxies. Although they can detect them, the above image features a photogenic superposition during a dark night in New Zealand about two weeks ago. As pictured above, the central part of our Milky Way Galaxy is seen rising to the east on the image left and arching high overhead. Beneath the Galactic arc and just above the horizon are the two brightest satellite galaxies of our Milky Way, with the Small Magellanic Cloud to the left and the Large Magellanic Cloud on the right. The radio dish is the Warkworth Satellite Station located just...

Explanation: What if we X-rayed an entire spiral galaxy? This was done (again) recently by NASA's Chandra X-ray Observatory for the nearby interacting galaxies known as the Whirlpool (M51). Hundreds of glittering x-ray stars are present in the above Chandra image of the spiral and its neighbor. The image is a conglomerate of X-ray light from Chandra and visible light from the Hubble Space Telescope. The number of luminous x-ray sources, likely neutron star and black hole binary systems within the confines of M51, is unusually high for normal spiral or elliptical galaxies and suggests this cosmic whirlpool has experienced...

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...

Explanation: Jewels don't shine this bright -- only stars do. Like gems in a jewel box, though, the stars of open cluster NGC 290 glitter in a beautiful display of brightness and color. The photogenic cluster, pictured above, was captured recently by the orbiting Hubble Space Telescope. Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters of stars. NGC 290 lies about 200,000 light-years distant in a neighboring galaxy called the Small Cloud of Magellan (SMC). The open cluster contains hundreds of stars and spans about 65...

Explanation: A star cluster around 2 million years young, M16 is surrounded by natal clouds of dust and glowing gas also known as The Eagle Nebula. This beautifully detailed image of the region includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the left edge of the frame is another...

Explanation: Sweeping slowly through northern skies, the comet PanSTARRS C/2012 K1 posed for this telescopic portrait on June 2nd in the constellation Ursa Major. Now within the inner solar system, the icy body from the Oort cloud sports two tails, a lighter broad dust tail and crooked ion tail extending below and right. The comet's condensed greenish coma makes a nice contrast with the spiky yellowish background star above. NGC 3319 appears at the upper left of the frame that spans almost twice the apparent diameter of the full Moon. The spiral galaxy is about 47 million light-years away, far...

Explanation: Galaxies like colorful pieces of candy fill the Hubble Ultra Deep Field 2014. The dimmest galaxies are more than 10 billion times fainter than stars visible to the unaided eye and represent the Universe in the extreme past, a few 100 million years after the Big Bang. The image itself was made with the significant addition of ultraviolet data to the Hubble Ultra Deep Field, an update of Hubble's famous most distant gaze toward the southern constellation of Fornax. It now covers the entire range of wavelengths available to Hubble's cameras, from ultraviolet through visible to near-infrared. Ultraviolet data...

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 the Sun. The truth is the green flash does exist and its cause is well understood. Just as the setting Sun disappears completely from view, a last glimmer appears startlingly green. 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 rising Sun, but takes better timing to spot. A dramatic green flash,...

Explanation: Might this giant pinwheel one-day destroy us? Probably not, but investigation of the unusual star system Wolf-Rayet 104 has turned up an unexpected threat. The unusual pinwheel pattern has been found to be created by energetic winds of gas and dust that are expelled and intertwine as two massive stars orbit each other. One system component is a Wolf-Rayet star, a tumultuous orb in the last stage of evolution before it explodes in a supernova -- an event possible anytime in the next million years. Research into the spiral pattern of the emitted dust, however, indicates the we are...

Astronomers using the Hubble Space Telescope have captured the most comprehensive picture ever assembled of the evolving universe—and one of the most colorful. The study is called the Ultraviolet Coverage of the Hubble Ultra Deep Field project. Prior to this survey, astronomers were in a curious position. They knew a lot about star formation occurring in nearby galaxies thanks to UV telescope facilities such as NASA's Galex observatory, which operated from 2003 to 2013. And, thanks to Hubble's near-infrared and visible capability, they had also studied star birth in the most distant galaxies. We see these distant galaxies in their...

Explanation: The space station has caught a dragon. Specifically, in mid-April, the International Space Station captured the unmanned SpaceX Dragon capsule sent to resupply the orbiting outpost. Pictured above, the station's Canadarm2 had just grabbed the commercial spaceship. The Dragon capsule was filled with over 5000 lbs (2260 kilos) of supplies and experiments to be used by the current band of six ISS astronauts that compose Expedition 39, as well as the six astronauts that compose Expedition 40. After docking with the ISS, the Dragon capsule was unloaded and eventually released, splashing down in the Pacific Ocean on May 18....

NASA has been talking about sending people to Mars by 2035. That goal is still on the books, despite recent upheaval in the space program, according to two of the agency's top scientists. "In the near term, Mars remains our primary focus," Ellen Stofan, NASA's chief scientist said May 15 in a talk at the Royal Institution in London ... ....scientists [also] decided to "redirect" an asteroid into an orbit of the moon and are searching for an asteroid that's an appropriate candidate. "Once we find the right one, we'll use all the technology we've got," he said. "We'll snag...

Explanation: The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its haunting symmetries are seen in the very central region of this stunning false-color picture, processed to reveal the enormous but extremely faint halo of gaseous material, over three light-years across, which surrounds the brighter, familiar planetary nebula. Made with data from the Nordic Optical Telescope in the Canary Islands, the composite picture shows extended emission from the nebula. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. Only much more recently however, have...

Explanation: This clear night skyscape captures the colorful glow of aurora australis, the southern lights, just outside the port city of Hobart, Tasmania, Australia, planet Earth. As if staring into the dreamlike scene, the Tasmanian Earth Resources Satellite Station poses in the center, illuminated by nearby city lights. Used to receive data from spacebased Earth observing instruments, including NASA's MODIS and SeaWiFS, the station was decommissioned in 2011 and dismantled only recently, shortly after the picture was taken on April 30. Still shining in southern skies though, the central bulge of our Milky Way galaxy and two bright satellite galaxies...