Η διαστημική φωτογραφία της ημέρας - Αρχείο

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 19

Ring Galaxy AM 0644-741 from Hubble

Image Credit: Hubble Heritage Team (AURA / STScI), J. Higdon (Cornell) ESA, NASA

Explanation: How could a galaxy become shaped like a ring? The rim of the blue galaxy pictured on the right is an immense ring-like structure 150,000 light years in diameter composed of newly formed, extremely bright, massive stars. That galaxy, AM 0644-741, is known as a ring galaxy and was caused by an immense galaxy collision. When galaxies collide, they pass through each other -- their individual stars rarely come into contact. The ring-like shape is the result of the gravitational disruption caused by an entire small intruder galaxy passing through a large one. When this happens, interstellar gas and dust become condensed, causing a wave of star formation to move out from the impact point like a ripple across the surface of a pond. The intruder galaxy is just outside of the frame taken by the Hubble Space Telescope. This featured image was taken to commemorate the anniversary of Hubble's launch in 1990. Ring galaxy AM 0644-741 lies about 300 million light years away.

Tomorrow's picture: one eclipse every three minutes

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 20

Total Solar Eclipse over Svalbard
Image Credit & Copyright: Thanakrit Santikunaporn

Explanation: Going, going, gone. That was the feeling in Svalbard, Norway last month during a total eclipse of the Sun by the Moon. In the featured image, the eclipse was captured every three minutes and then digitally merged with a foreground frame taken from the same location. Visible in the foreground are numerous gawking eclipse seekers, some deploying pretty sophisticated cameras. As the Moon and Sun moved together across the sky -- nearly horizontally from this far north -- an increasing fraction of the Sun appears covered by the Moon. In the central frame, the Moon's complete blockage of the disk of the Sun makes the immediate surroundings appear like night during the day. The exception is the Moon itself, which now appears surrounded by the expansive corona of the Sun. Of course, about 2.5 minutes later, the surface of the Sun began to reappear. The next total eclipse of the Sun will occur in 2016 March and be visible from Southeast Asia.

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Tomorrow's picture: explore an asteroid

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[Xenios]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 22

Colorful Star Clouds in Cygnus
Image Credit & Copyright: André van der Hoeven

Explanation: Stars can form in colorful surroundings. Featured here is a star forming region rich in glowing gas and dark dust toward the constellation of the Swan (Cygnus), near the bright star Sadr. This region, which spans about 50 light years, is part of the Gamma Cygni nebula which lies about 1,800 light years distant. Toward the right of the image is Barnard 344, a dark and twisted dust cloud rich in cool molecular gas. A dramatic wall of dust and red-glowing hydrogen gas forms a line down the picture center. While the glowing red gas is indicative of small emission nebulas, the blue tinted areas are reflection nebulas -- starlight reflecting from usually dark dust grains. The Gamma Cygni nebula will likely not last the next billion years, as most of the bright young stars will explode, most of the dust will be destroyed, and most of the gas will drift away.

Explore a Virtual Universe: Random APOD Generator
Tomorrow's picture: explore an asteroid

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[Xenios]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 23

Meteor in the Milky Way
Image Credit & Copyright: Marko Korosec

Explanation: Earth's April showers include the Lyrid Meteor Shower, observed for more than 2,000 years when the planet makes its annual passage through the dust stream of long-period Comet Thatcher. A grain of that comet's dust, moving 48 kilometers per second at an altitude of 100 kilometers or so, is swept up in this night sky view from the early hours of April 21. Flashing toward the southeastern horizon, the meteor's brilliant streak crosses the central region of the rising Milky Way. Its trail points back toward the shower's radiant in the constellation Lyra, high in the northern springtime sky and off the top of the frame. The yellowish hue of giant star Antares shines to the right of the Milky Way's bulge. Higher still is bright planet Saturn, near the right edge. Seen from Istra, Croatia, the Lyrid meteor's greenish glow reflects in the waters of the Adriatic Sea.

Tomorrow's picture: Noctiluca scintillans

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 24

Blue Tears and the Milky Way
Image Credit & Copyright: Rogelio Bernal Andreo (Deep Sky Colors)

Explanation: Lapping at rocks along the shore of the Island of Nangan, Taiwan, planet Earth, waves are infused with a subtle blue light in this sea and night skyscape. Composed of a series of long exposures made on April 16 the image captures the faint glow from Noctiluca scintillans. Also known as sea sparkles or blue tears, the marine plankton's bioluminescence is stimulated by wave motion. City lights along the coast of mainland China shine beneath low clouds in the west but stars and the faint Milky Way still fill the night above. Over the horizon the galaxy's central bulge and dark rifts seem to echo the rocks and luminous waves.

Tomorrow's picture: star party

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[Xenios]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 25

Cluster and Starforming Region Westerlund 2
Image Credit & Copyright: NASA, ESA, the Hubble Heritage Team

(STScI / AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team

Explanation: Located 20,000 light-years away in the constellation Carina, the young cluster and starforming region Westerlund 2 fills this cosmic scene. Captured with Hubble's cameras in near-infrared and visible light, the stunning image is a celebration of the 25th anniversary of the launch of the Hubble Space Telescope on April 24, 1990. The cluster's dense concentration of luminous, massive stars is about 10 light-years across. Strong winds and radiation from those massive young stars have sculpted and shaped the region's gas and dust, into starforming pillars that point back to the central cluster. Red dots surrounding the bright stars are the cluster's faint newborn stars, still within their natal gas and dust cocoons. But brighter blue stars scattered around are likely not in the Westerlund 2 cluster and instead lie in the foreground of the Hubble anniversary field of view.

Tomorrow's picture: cosmic entomology

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 26

Planetary Nebula Mz3: The Ant Nebula
Image Credit: R. Sahai (JPL) et al., Hubble Heritage Team, ESA, NASA

Explanation: Why isn't this ant a big sphere? Planetary nebula Mz3 is being cast off by a star similar to our Sun that is, surely, round. Why then would the gas that is streaming away create an ant-shaped nebula that is distinctly not round? Clues might include the high 1000-kilometer per second speed of the expelled gas, the light-year long length of the structure, and the magnetism of the star visible above at the nebula's center. One possible answer is that Mz3 is hiding a second, dimmer star that orbits close in to the bright star. A competing hypothesis holds that the central star's own spin and magnetic field are channeling the gas. Since the central star appears to be so similar to our own Sun, astronomers hope that increased understanding of the history of this giant space ant can provide useful insight into the likely future of our own Sun and Earth.

Celebration: 25 Years of the Hubble Space Telescope
Tomorrow's picture: terminator station

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 27

Space Station over Lunar Terminator
Image Credit & Copyright: Dani Caxete

Explanation: What's that in front of the Moon? It's the International Space Station. Using precise timing, the Earth-orbiting space platform was photographed in front of a partially lit Moon last year. The featured image was taken from Madrid, Spain with an exposure time of only 1/1000 of a second. In contrast, the duration of the transit of the ISS across the entire Moon was about half a second. The sun-glinting station can be seen just to the dark side of the day / night line known as the terminator. Numerous circular craters are visible on the distant Moon, as well as comparatively rough, light colored terrain known as highlands, and relatively smooth, dark colored areas known as maria. On-line tools can tell you when the International Space Station will be visible from your area.

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Tomorrow's picture: amazing spiral

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[Xenios]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 28

Massive Nearby Spiral Galaxy NGC 2841

Image Credit: Hubble, Subaru; Composition & Copyright: Roberto Colombari

Explanation: It is one of the more massive galaxies known. A mere 46 million light-years distant, spiral galaxy NGC 2841 can be found in the northern constellation of Ursa Major. This sharp view of the gorgeous island universe shows off a striking yellow nucleus and galactic disk. Dust lanes, small, pink star-forming regions, and young blue star clusters are embedded in the patchy, tightly wound spiral arms. In contrast, many other spirals exhibit grand, sweeping arms with large star-forming regions. NGC 2841 has a diameter of over 150,000 light-years, even larger than our own Milky Way and captured by this composite image merging exposures from the orbiting 2.4-meter Hubble Space Telescope and the ground-based 8.2-meter Subaru Telescope. X-ray images suggest that resulting winds and stellar explosions create plumes of hot gas extending into a halo around NGC 2841.

Tomorrow's picture: comet tailing

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 29

Comet Churyumov Gerasimenko in Crescent
Image Credit: ESA, Rosetta, NAVCAM; processing by Giuseppe Conzo

Explanation: What's happening to Comet 67P/Churyumov–Gerasimenko? As the 3-km wide comet moves closer to the Sun, heat causes the nucleus to expel gas and dust. The Rosetta spacecraft arrived at the comet's craggily double nucleus last July and now is co-orbiting the Sun with the giant dark iceberg. Recent analysis of data beamed back to Earth from the robotic Rosetta spacecraft has shown that water being expelled by 67P has a significant difference with water on Earth, indicating that Earth's water could not have originated from ancient collisions with comets like 67P. Additionally, neither Rosetta nor its Philae lander detected a magnetic field around the comet nucleus, indicating that magnetism might have been unimportant in the evolution of the early Solar System. Comet 67P, shown in a crescent phase in false color, should increase its evaporation rate as it nears its closest approach to the Sun in 2015 August, when it reaches a Sun distance just a bit further out than the Earth.

Tomorrow's picture: open space

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 April 30

Across the Sun
Image Credit & Copyright: Göran Strand

Explanation: A long solar filament stretches across the relatively calm surface of the Sun in this telescopic snap shot from April 27. The negative or inverted narrowband image was made in the light of ionized hydrogen atoms. Seen at the upper left, the magnificent curtain of magnetized plasma towers above surface and actually reaches beyond the Sun's edge. How long is the solar filament? About as long as the distance from Earth to Moon, illustrated by the scale insert at the left. Tracking toward the right across the solar disk a day later the long filament erupted, lifting away from the Sun's surface. Monitored by Sun staring satellites, a coronal mass ejection was also blasted from the site but is expected to swing wide of our fair planet.

Tomorrow's picture: days in the Sun

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 May 1

MESSENGER's Last Day on Mercury
Image Credit: NASA, Johns Hopkins Univ. APL, Arizona State Univ., CIW

Explanation: The first to orbit Mercury, the MESSENGER spacecraft came to rest on this region of Mercury's surface yesterday. Constructed from MESSENGER image and laser altimeter data, the scene looks north over the northeastern rim of the broad, lava filled Shakespeare basin. The large, 48 kilometer (30 mile) wide crater Janacek is near the upper left edge. Terrain height is color coded with red regions about 3 kilometers above blue ones. MESSENGER'S final orbit was predicted to end near the center, with the spacecraft impacting the surface at nearly 4 kilometers per second (over 87,000 miles per hour) and creating a new crater about 16 meters (52 feet) in diameter. The impact on the far side of Mercury was not observed by telescopes, but confirmed when no signal was detected from the spacecraft given time to emerge from behind the planet. Launched in 2004, the MErcury Surface, Space ENvironment, GEochemisty and Ranging spacecraft completed over 4,000 orbits after reaching the Solar System's innermost planet in 2011.

Tomorrow's picture: cosmic whirlpool

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 May 2

M51: The Whirlpool Galaxy
Image Credit & Copyright: Martin Pugh

Explanation: Follow the handle of the Big Dipper away from the dipper's bowl until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the eye, deep images like this one can reveal striking colors and the faint tidal debris around the smaller galaxy

Tomorrow's picture: Sunday's shadow

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 May 3

Moonrise Through Mauna Kea's Shadow
Image Credit & Copyright: Michael Connelley (U. Hawaii)

Explanation: How can the Moon rise through a mountain? It cannot -- what was photographed here is a moonrise through the shadow of a large volcano. The volcano is Mauna Kea, Hawai'i, USA, a frequent spot for spectacular photographs since it is arguably the premier observing location on planet Earth. The Sun has just set in the opposite direction, behind the camera. Additionally, the Moon has just passed full phase -- were it precisely at full phase it would rise, possibly eclipsed, at the very peak of the shadow. The Moon is actually rising in the triangular shadow cone of the volcano, a corridor of darkness that tapers off in the distance like converging train tracks. The Moon is too large and too far away to be affected by the shadow of the volcano. Refraction of moonlight through the Earth's atmosphere makes the Moon appear slightly oval. Cinder cones from old volcanic eruptions are visible in the foreground.

Tomorrow's picture: aurora moon

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2015 May 4

An Unexpected Aurora over Norway
Image Credit & Copyright: Tommy Richardsen

Explanation: Sometimes the sky lights up unexpectedly. A trip to northern Norway to photograph auroras was not going as well as hoped. It was now past midnight in Steinsvik, Troms, in northern Norway, and the date was 2014 February 8. Despite recent activity on the Sun, the skies were disappointing. Therefore, the astrophotographer began packing up to go. His brother began searching for a missing lens cap. When the sky suddenly exploded with spectacular aurora. Reacting quickly, a sequence detailing dramatic green curtains was captured, with the bright Moon near the image center, and the lens-cap seeking brother on the far right. The auroral flare lasted only a few minutes, but the memory of this event, the photographer speculates, will last much longer.

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Tomorrow's picture: heavy mercury

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