Astronomy Picture of the Day

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.
2008 June 20

Solstice Moonrise, Cape Sounion
Credit & Copyright: Anthony Ayiomamitis (TWAN) Explanation: Today's solstice marks the northernmost point of the Sun's annual motion through planet Earth's sky and the astronomical beginning of the northern hemisphere's summer. But only two days ago, the Full Moon nearest the solstice rose close to the ecliptic plane opposite the Sun, near its southernmost point for the year. Astronomer Anthony Ayiomamitis recorded this dramatic picture of the solstice Full Moon rising above Cape Sounion, Greece. The twenty-four hundred year old Temple of Poseidon lies in the foreground, also visible to sailors on the Aegean Sea. In this well-planned single exposure, a telescopic lens makes the Moon loom large, but even without optical aid casual skygazers often find the Full Moon looking astonishingly large when seen near the horizon. That powerful visual effect is known as the Moon Illusion.


Tomorrow's picture: light-weekend

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.
2008 June 28

Fireball at Ayers Rock
Credit & Copyright: Joseph Brimacombe Explanation: A weekend trip for astrophotography in central Australia can result in gorgeous skyscapes. In this example recorded in March of 2006, the center of our Milky Way Galaxy rises over planet Earth's horizon and the large sandstone formation called Uluru, also known as Ayers Rock. After setting up two cameras to automatically image this celestial scene in a series of exposures, one through a wide-angle and the other through a telephoto lens, photographer Joseph Brimacombe briefly turned his back to set up other equipment. To his surprise, the ground around him suddenly lit up with the brilliant flash of a fireball meteor. To his delight, both cameras captured the bright meteor streak. Highlighted in the telephoto view (inset), the fireball trail shines through cloud banks, just left of Ayers Rock.


Tomorrow's picture: light-weekend

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.
2008 July 1

Pickering's Triangle from Kitt Peak
Credit & Copyright: T. Rector (U. Alaska Anchorage), H. Schweiker, WIYN, NOAO, AURA, NSF Explanation: Wisps like this are all that remain visible of a Milky Way star. About 7,500 years ago that star exploded in a supernova leaving the Veil Nebula, also known as the Cygnus Loop. At the time, the expanding cloud was likely as bright as a crescent Moon, remaining visible for weeks to people living at the dawn of recorded history. Today, the resulting supernova remnant has faded and is now visible only through a small telescope directed toward the constellation of Cygnus. The remaining Veil Nebula is physically huge, however, and even though it lies about 1,400 light-years distant, it covers over five times the size of the full Moon. In images of the complete Veil Nebula, studious readers should be able to identify the Pickering's Triangle component pictured above, a component named for a famous astronomer and the wisp's approximate shape. The above image is a mosaic from the 4-meter Mayall telescope at the Kitt Peak National Observatory located in Arizona, USA.


Tomorrow's picture: jerry's wednesday

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.
2008 July 2

Night Shinings
Credit & Copyright: Laurent Laveder (PixHeaven.net / TWAN) Explanation: In the early morning hours of June 30th, ghostly clouds hovered in the east in this view of near dawn skies over western France. The noctilucent or night-shining clouds lie near the edge of space, reflecting sunlight from about 80 kilometers above Earth's surface. Usually spotted above the poles in summer, they are now seen with increasing frequency farther from the poles, in this case extending to the photographer's latitude of about 48 degrees north. The trend could be a telltale sign of global changes in the atmosphere. Another 400,000 kilometers away, the Moon's sunlit crescent shines brightly, its night side illuminated by Earthshine. Of course, as a bonus for early risers June's old crescent Moon was followed closely across the sky by the lovely Pleiades star cluster, surrounded by cosmic dust clouds and shining from a mere 400 light-years away.


Tomorrow's picture: pixels in space

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.
2008 July 4

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.
2008 July 5

Comet Between Fireworks and Lightning
Credit & Copyright: Antti Kemppainen Explanation: Sometimes the sky itself is the best show in town. Last January, people from Perth, Australia gathered on a local beach to watch a sky light up with delights near and far. Nearby, fireworks exploded as part of Australia Day celebrations. On the far right, lightning from a thunderstorm flashed in the distance. Near the image center, though, seen through clouds, was the most unusual sight of all: Comet McNaught. The photogenic comet was so bright that it even remained visible though the din of Earthly flashes. Comet McNaught has now returned to the outer Solar System and is now only visible with a large telescope. The above image is actually a three photograph panorama digitally processed to reduce red reflections from the exploding firework.


Tomorrow's picture: Sunday's Childe

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.
2008 July 7

The Southern Cross in a Southern Sky
Credit & Copyright: Yuri Beletsky (ESO) Explanation: This breathtaking patch of sky would be above you were you to stand at the South Pole of the Earth. On the upper left of this image are the four stars that mark the boundaries of the famous Southern Cross. At the top of this constellation, also known as The Crux, is the orange star Gamma Crucis. The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy. Just below the Southern Cross on the far left is the dark Coal Sack Nebula, and the bright nebula on the far right is the Carina Nebula. The Southern Cross is such a famous constellation that it is depicted on the national flag of Australia.


Tomorrow's picture: innocent galaxies

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.
2008 July 9
Planets and Fire by Moonlight
Credit & Copyright: Dmitrii Zagorodnov
Explanation: On July 5th, wandering planets, bright stars, and a young crescent Moon graced western skies after sunset. Arrayed along the solar system's ecliptic plane, the three celestial beacons forming this slyscape's eye-catching line-up with the Moon are Saturn (upper left), then Mars, and finally Regulus, alpha star of the constellation Leo. Of course planet Earth itself lies in the foreground, a scene dominated by the city lights of Santa Barbara, California. The smoky haze hanging over the city is from threatening wild fires still burning along the hill at the right. On Thursday evening, Saturn and Mars can be seen in a much closer pairing or conjunction, separated by only about 3/4 degree on the sly.

Tomorrow's picture: at Mercury

<div align="center"> 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.
2008 July 11

The Far 3kpc Arm
Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA
Explanation: A major discovery was lurking in the data. By accident, while preparing a talk on the Galaxy's spiral arms for a meeting of the American Astronomical Society, Tom Dame (Harvard-Smithsonian CfA) found it - a new spiral arm in the Milky Way. The arm is labeled in this illustration as the Far 3kpc Arm, located at a distance of 3 kpc (kiloparsecs) or about 10,000 light-years from the galactic center, on the opposite side from the Sun. Along with the Near 3kpc Arm whose presence was known since the mid 1950s, the counterpart inner arms now establish that the galaxy has a simple symmetry. The arms are defined by shocked interstellar gas flowing along both sides of the Milky Way's central bar. Dame and his collaborator Patrick Thaddeus recorded the presence of both inner spiral arms in their radio data tracking emission from carbon monoxide molecules along the galactic plane. How much star formation goes on in the counterpart arms? Despite this depiction of stars and star forming regions along the arms, the last attempt to search for star formation in the Near 3kpc Arm was in 1980 and didn't turn up any. The discovery of the Far 3kpc Arm has renewed