Astronomy fanatica
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Astronomy Picture of the Day
2006 February 15
Rotating Titan in Infrared Light
Explanation: Titan is one of the strangest places in our Solar System. The only moon known with thick clouds, this unusual satellite of Saturn shows evidence of evaporating lakes created by methane rain. The clouds that make Titan featureless in visible light have now been imaged several times in infrared light by the robot Cassini spacecraft currently orbiting Saturn. These images have been compiled into the above time-lapse movie. Like Earth's Moon, Titan always shows the same face toward its central planet. It therefore takes Titan about 16 days to complete one rotation. Titan has numerous areas of light terrain with some large areas of dark terrain visible near the equator. Small areas of brightest terrain might arise from ice-volcanoes and have a high amount of reflective frozen water-ice. Titan's surface was imaged for the first time early last year by the Huygens probe, which survived for three hours on a cold and sandy dark region.
Credit: VIMS Team, U. Arizona, ESA, NASA -
Astronomy Picture of the Day
2006 February 16
The Color of the Moon
Explanation: Earth's Moon is normally seen in subtle shades of grey or yellow. But small color differences have been greatly exaggerated to make this dramatic mosaic image of the Moon's gibbous phase. The familiar Sea of Tranquility (Mare Tranquillitatis) is the blue area right of center. White lines radiate from the crater Tycho at bottom left, while purplish tones mottle the crater Copernicus left of center. Though exaggerated, the different colors are recognized to correspond to real differences in the chemical makeup of the lunar surface - blue hues reveal titanium rich areas while orange and purple colors show regions relatively poor in titanium and iron. Calibrated by rock samples from the Apollo missions, similar multicolor images from spacecraft have been used to explore the Moon's global surface composition.
Credit & Copyright: Johannes Schedler (Panther Observatory) -
Astronomy Picture of the Day
2006 February 17
Supernova Remnant and Shock Wave
Explanation: A massive star ends life as a supernova, blasting its outer layers back to interstellar space. The spectacular death explosion is initiated by the collapse of what has become an impossibly dense stellar core. Pictured is the expanding supernova remnant Puppis A - one of the brightest sources in the x-ray sky. Now seen to be about 10 light-years in diameter, light from the initial stellar explosion first reached Earth a few thousand years ago. Recorded by the Chandra Observatory's x-ray cameras, the inset view shows striking details of the strong shock wave disrupting an interstellar cloud as the shock sweeps through preexisting material. The larger field ROSAT image also captures a of pinpoint source of x-rays near the remnant's center. The source is a young neutron star, the remnant of the collapsed stellar core kicked out by the explosion and moving away at about 1,000 kilometers per second.
Credit: Chandra: NASA / CXC / GSFC, U.Hwang et al.; ROSAT: NASA/GSFC/S.Snowden et al. -
Astronomy Picture of the Day
2006 February 18
Mir Dreams
Explanation: This dream-like image of Mir was recorded by astronauts as the space shuttle orbiter Atlantis approached the Russian space station prior to docking during the STS-76 mission in 1996. Sporting spindly appendages and solar panels, Mir resembles a whimsical flying insect hovering about 350 kilometers above New Zealand's South Island and the city of Nelson near Cook Strait. Mir was launched 20 years ago this week, and served as a continuously occupied orbital outpost until August 1999. Mir was visited by over 100 spacefarers from the nations of planet Earth including, Russia, the United States, Great Britain, Germany, France, Japan, Austria, Kazakhstan and Slovakia. The Mir was deorbited in March 2001.
Credit: STS-76 Crew, NASA -
Astronomy Picture of the Day
2006 February 19
M51: The Whirlpool Galaxy in Dust and Stars
Explanation: The Whirlpool Galaxy is a classic spiral galaxy. At only 30 million light years distant and fully 60 thousand light years across, M51, also known as NGC 5194, is one of the brightest and most picturesque galaxies on the sky. The above image is a digital combination of a ground-based image from the 0.9-meter telescope at Kitt Peak National Observatory and a space-based image from the Hubble Space Telescope highlighting sharp features normally too red to be seen. Anyone with a good pair of binoculars, however, can see this Whirlpool toward the constellation of Canes Venatici. M51 is a spiral galaxy of type Sc and is the dominant member of a whole group of galaxies. Astronomers speculate that M51's spiral structure is primarily due to its gravitational interaction with a smaller galaxy just off the top of this digitally sharpened image.
Credit: N. Scoville (Caltech), T. Rector (U. Alaska, NOAO) et al., Hubble Heritage Team, NASA -
Astronomy Picture of the Day
2006 February 20
SuitSat-1: A Spacesuit Floats Free
Explanation: Who dunnit? Like a scene from a space mystery movie, a spacesuit floated away from the International Space Station earlier this month, but no investigation was needed. It was pushed out by the space station crew. Dubbed Suitsat-1, the unneeded Russian Orlan spacesuit filled mostly with old clothes was fitted with a faint radio transmitter and released to orbit the Earth. Suitsat-1 will orbit once every 90 minutes until it burns up in the Earth's atmosphere within a few weeks. The suit circled the Earth twice before its radio signal became unexpectedly weak. Pictured above, the lifeless spacesuit was photographed as it drifted away from the Earth-orbiting space station earlier this month.
Credit: ISS Expedition 12 Crew, NASA -
Astronomy Picture of the Day
2006 February 21
Wisps Surrounding the Horsehead Nebula
Explanation: The famous Horsehead Nebula in Orion is not alone. A deep exposure shows that the dark familiar shaped indentation, visible just below center, is part of a vast complex of absorbing dust and glowing gas. To bring out details of the Horsehead's pasture, amateur astronomers at the Star Shadow Remote Observatory in New Mexico, USA fixed a small telescope on the region for over seven hours filtering out all but a very specific color of red light emitted by hydrogen. They then added the image to a full color frame taken over three hours. The resulting spectacular picture details an intricate tapestry of gaseous wisps and dust-laden filaments that were created and sculpted over eons by stellar winds and ancient supernovas. The Horsehead Nebula lies 1,500 light years distant towards the constellation of Orion. Two stars from the Orion's Belt can be found in the above image.
Credit & Copyright: Star Shadows Remote Observatory -
Astronomy Picture of the Day
2006 February 22
An Unusually Smooth Surface on Saturn's Telesto
Explanation: Why is Saturn's small moon Telesto so smooth? Possibly Telesto is covered with a type of granular icy material similar to that suspected of covering Pandora, another of Saturn's small moons. If so, Telesto might be more like a pile of rubble than a solid body. This recently uncovered Solar System mystery is currently a topic of research, however. The unexpected finding originated last October when the robot Cassini spacecraft, currently orbiting Saturn, swooped past the 24-kilometer moon and captured the first ever image of Telesto's surface. Telesto orbits Saturn always just ahead of the much larger moon Tethys. Pictured above, Telesto's unusually smooth surface was found to show some large craters and boulders, but not the high density of craters found on nearby Tethys or most other Saturnian moons.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA -
Astronomy Picture of the Day
2006 February 23
Saturn Storm by Ringshine
Explanation: Imaged on the night side of Saturn by the Cassini spacecraft, these swirling storm clouds are illuminated by ringshine - sunlight reflected from the gas giant's magnificent ring system. The storm (top) was actually spotted last month by amateur astronomers as it rotated across Saturn's day side and spans about 3,500 kilometers. When the storm was on the same side of Saturn as the Cassini spacecraft, bursts of radio noise were detected, suggesting lightning discharges connected with the storm were responsible for the radio emission. While no lightning is seen directly in this Cassini image, scientists note that this storm appears along the planet's southern hemisphere storm alley in approximately the same location as Saturn's Dragon Storm, reported early last year. Though the new storm is larger and seems to be more powerful, it could well be the Dragon Storm reemerging.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA -
Astronomy Picture of the Day
2006 February 24
Recurrent Nova RS Ophiuci
Explanation: This pretty star field in the constellation Ophiucus is centered on a star not often seen - RS Ophiuci. In fact, early last week RS Oph suddenly became visible to the naked eye for the first time since 1985. A type of cataclysmic variable star classified as a recurrent nova, RS Oph dramatically increased in brightness from 11th magnitude, too faint to appear on some star charts. Historically, RS Oph was seen to go through only four similar outbursts since 1898. Such stars are now modeled as interacting binary star systems, composed of a compact white dwarf star co-orbiting with a swollen red giant. As material falls away from the red giant it collects in a rotating accretion disk before ultimately falling on to the white dwarf. Disk instabilities, or a build up of material on the compact star result in the occasional but rapid release of energy through nuclear burning. At an estimated distance of 3,000 light-years, RS Ophiuci is now reported to be fading rapidly. This telescopic view spans about 2 degrees (4 full moons) and was captured on the morning of February 16 from the RAS Observatory under New Mexico skies.
Credit & Copyright: John Chumack -
Astronomy Picture of the Day
2006 February 25
SOFIA's Window Seat
Explanation: Earlier this month, a 2.5-meter diameter infrared telescope was permanently assigned a window seat, looking through this opening in the fuselage of a historic Boeing 747 aircraft. The telescope mirror, about the size of the Hubble Space Telescope mirror, is protected by a red covering. Known as the Stratospheric Observatory For Infrared Astronomy (SOFIA), the airborne observatory is intended to fly at altitudes up to 45,000 feet - above more than 99% of the atmospheric water vapor. Water vapor strongly absorbs infrared light, so at that altitude SOFIA will be able to acquire infrared images not possible for even the largest ground-based telescopes. SOFIA's unique capabilities will include the ability to trace complex molecules in the cosmic environments surrounding star birth and death and the formation of new solar systems. The SOFIA aircraft was operated by Pan American World Airways and was originally christened the "Clipper Lindbergh". The airborne observatory was designed with an on board console for teachers and other educators to participate in research flights.
Credit: Courtesy Dana Backman (SETI Institute), USRA, L-3 -
Astronomy Picture of the Day
2006 February 26
Inside the Eagle Nebula
Explanation: From afar, the whole thing looks like an Eagle. A closer look at the Eagle Nebula, however, shows the bright region is actually a window into the center of a larger dark shell of dust. Through this window, a brightly-lit workshop appears where a whole open cluster of stars is being formed. In this cavity tall pillars and round globules of dark dust and cold molecular gas remain where stars are still forming. Already visible are several young bright blue stars whose light and winds are burning away and pushing back the remaining filaments and walls of gas and dust. The Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of Serpens. The above picture combines three specific emitted colors and was taken with the 0.9-meter telescope on Kitt Peak, Arizona, USA.
Credit & Copyright: T. A. Rector & B. A. Wolpa, NOAO, AURA -
Astronomy Picture of the Day
2006 February 27
GRB 060218: A Mysterious Transient
Explanation: What is it? Something is happening in a small portion of the sky toward the constellation of Aries and telescopes around the globe are tracking an unusual transient there as it changes day by day. No one is sure what it will do next. The entire space mystery began on February 18 when the Earth-orbiting robot Swift satellite noticed an unusual transient began to glow dimly in gamma rays. Dubbed GRB 060218, the object is a type of gamma ray burst (GRB) but the way its brightness changes is very unusual. Since detection, GRB 060218 has been found to emit light across the electromagnetic spectrum, including radio waves and visible light. Pictured above, the Sloan Digital Sky Survey (SDSS) image of the field of GRB 060218 well prior to its Swift trigger is shown on the left, while the same field, taken by the orbiting Swift satellites' ultraviolet telescope after the Swift trigger, is shown on the right. The oddball GRB is visible in the center of the right image. Subsequent observations found a redshift for the transient of z=0.033, showing it to be only about 440 million light years away, relatively nearby compared to typical GRBs. Whether GRB 060218 represents a new type of gamma ray burst, a new type of supernova, or an unusual link between the GRBs and supernovas has become an instant topic of research.
Credit: SDSS Collaboration, Swift Collaboration, Sloan Foundation, NSF, NASA -
Astronomy Picture of the Day
2006 February 28
The Flaming Star Nebula from CFHT
Explanation: Rippling dust and gas lanes give the Flaming Star Nebula its name. The red and purple colors of the nebula are present in different regions and are created by different processes. The bright star AE Aurigae, visible toward the image left, is so hot it is blue, emitting light so energetic it knocks electrons away from surrounding gas. When a proton recaptures an electron, red light is frequently emitted. The purple region's color is a mix of this red light and blue light emitted by AE Aurigae but reflected to us by surrounding dust. The two regions are referred to as emission nebula and reflection nebula, respectively. Pictured above, the Flaming Star Nebula, officially known as IC 405, lies about 1500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga).
Credit & Copyright: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT -
Astronomy Picture of the Day
2006 March 1
Multiverses: Do Other Universes Exist?
Explanation: Do nearly exact copies of you exist in other universes? If one or more of the multiverse hypotheses is correct, then quite possibly they do. In the above computer-enhanced illustration, independent universes are shown as independent circles or spheres. Spheres may be causally disconnected from all other spheres, meaning no communications can pass between them. Some spheres may contain different realizations of our universe, while others may have different physical laws. An entire set of parallel universes is called a multiverse. The human eye might represent the possibility that realizations of some multiverse hypotheses might only exist in the human mind. One criticism of multiverse hypotheses is that they are frequently difficult to test. Some multiverse hypotheses may therefore be great fun to think about but not practically falsifiable and therefore have no predictive scientific value.
Illustration Credit & Copyright: Clifford Pickover -
Astronomy Picture of the Day
2006 March 2
Messier 101
Explanation: Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier's famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way galaxy. M101 was also one of the original spiral nebulae observed by Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. Assembled from 51 exposures recorded by the Hubble Space Telescope in the 20th and 21st centuries, with additional data from ground based telescopes, this mosaic of M101 is touted as the largest, most detailed spiral galaxy view ever released from Hubble. The sharp image shows stunning features along the galaxy's face-on disk of stars and dust along with background galaxies, some visible right through M101 itself. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away.
Image Credit: NASA, ESA, CFHT, NOAO; Acknowledgement - K.Kuntz (GSFC), F.Bresolin (U.Hawaii), J.Trauger (JPL), J.Mould (NOAO), Y.-H.Chu (U. Illinois) -
Astronomy Picture of the Day
2006 March 3
Venus and Comet Pojmanski
Explanation: Shining brightly in the east at dawn, Venus dominates the sky in this view over a suburban landscape from Bursa, Turkey. An otherwise familiar scene for astronomer Tunc Tezel, his composite picture of the morning sky recorded on March 2nd also includes a surprise visitor to the inner solar system, Comet Pojmanski. Cataloged as C/2006 A1, the comet was discovered on January 2nd by Grzegorz Pojmanski of Warsaw University Astronomical Observatory in Poland. At the time very faint and tracking through southern skies, the comet has now moved north and grown just bright enough to be a good target for early-rising skygazers with binoculars. Enhanced and framed in this picture, the comet's tail has also grown to a length of several degrees. The comet will be at its closest approach to planet Earth, just over 100 million kilometers away, on March 5. For northern hemisphere observers in the next few days, the beginning of morning twilight really will be the best time to spot Comet Pojmanski.
Image Credit & Copyright: Tunc Tezel -
Astronomy Picture of the Day
2006 March 4
The Galaxy Within Centaurus A
Explanation: Peering deep inside Centaurus A, the closest active galaxy to Earth, the Spitzer Space Telescope's penetrating infrared cameras recorded this startling vista in February 2004. About 1,000 light-years across, the twisted cosmic dust cloud apparently shaped like a parallelogram is likely the result of a smaller spiral galaxy falling into the giant Centaurus A. The parallelogram lies along the active galaxy's central band of dust and stars visible in more familiar optical images. Astronomers believe that the striking geometric shape represents an approximately edge-on view of the infalling spiral galaxy's disk in the process of being twisted and warped by the interaction. Ultimately, debris from the ill-fated spiral galaxy should provide fuel for the supermassive black hole lurking at the center of Centaurus A.
Credit: J. Keene (SSC/Caltech) et al., JPL, Caltech, NASA -
Astronomy Picture of the Day
2006 March 5
Colorful Light Pillars
Explanation: How can an aurora appear so near the ground? Pictured above are not aurora but nearby light pillars, a local phenomenon that can appear as a distant one. In most places on Earth, a lucky viewer can see a Sun-pillar, a column of light appearing to extend up from the Sun caused by flat fluttering ice-crystals reflecting sunlight from the upper atmosphere. Usually these ice ice crystals evaporate before reaching the ground. During freezing temperatures, however, flat fluttering ice crystals may form near the ground in a form of light snow, sometimes known as a crystal fog. These ice crystals may then reflect ground lights in columns not unlike a Sun-pillar. In the above picture, the colorful lights causing the light pillars surround a ice-skating rink in Fairbanks, Alaska.
Credit & Copyright: Walter Tape (Alaska Fairbanks), Figure 8-1, Atmospheric Halos -
Astronomy Picture of the Day
2006 March 6
Unexpected Comet Pojmanski Now Visible
Explanation: Have you ever seen a comet? Comets bright enough to be visible to the unaided eye appear only every few years. Right now, however, a new comet has brightened unexpectedly and is visible as a faint streak to the unaided northern observer in the eastern morning sky just before sunrise. Binoculars may help. Comet Pojmanski, officially designated C/2006 A1 and discovered only in January, now sports a turquoise tail several times longer than the full moon. Comet Pojmanski's ion tail is due to gas particles expelled by the comet being pushed away from the Sun by the solar wind, the same wind that ionizes gas in the tail causing its blue tint. Pictured above as it appeared only last week, Comet Pojmanski has now begun to fade as its orbit around the Sun takes it further from the Earth.
Credit & Copyright: Chris Schur -
Astronomy Picture of the Day
2006 March 7
A Nearby Supernova in Spiral Galaxy M100
Explanation: One of the nearer supernovas of recent years was discovered last month in the bright nearby galaxy M100. The supernova, dubbed SN 2006X, is still near its maximum brightness and visible with a telescope toward the constellation of Berenice's Hair (Coma Berenices) The supernova, pictured above, has been identified as Type Ia indicating that a white dwarf star in the picturesque spiral galaxy has gone over its Chandrasekhar limit and exploded. Although hundreds of supernovas are now discovered each year by automated searches, nearby supernova are rare and important because they frequently become bright enough to be studied by many telescopes and are near enough for their immediate surroundings to be spatially resolved. Supernova 2006X's host galaxy M100 resides in the Virgo Cluster of Galaxies located about 50 million light years from Earth.
Credit: FORS Team, 8.2-meter VLT, ESO -
Astronomy Picture of the Day
2006 March 8
Earth's Shrinking Antarctic Ice Sheet
Explanation: Is the continent at the end of the Earth slowly melting? For millions of years, Antarctica, the frozen continent at the southern end of planet Earth, has been encased in a gigantic sheet of ice. Recently, the orbiting robotic GRACE satellite has been taking sensitive measurements of the gravity for the entire Earth, including Antarctica. Recent analysis of Gravity Recovery and Climate Experiment (GRACE) data indicate that the Antarctic ice sheet might have lost enough mass to cause the worlds' oceans to rise about 1.2 millimeters, on the average, from between 2002 and 2005. Although this may not seem like much, the equivalent amount of water is about 150 trillion liters, equivalent to the amount of water used by US residents in three months. Uncertainties in the measurement make the mass loss uncertain by about 80 trillion liters. Pictured above is an iceberg that is a small part of the Antarctic ice sheet. Future research will likely focus on trying to better understand the data, take more data, predict future trends, and understand possible effects of these trends on the future climate of our entire home planet.
Credit: Ben Holt Sr., GRACE team, DLR, NASA -
Astronomy Picture of the Day
2006 March 9
Trio Leo
Explanation: This popular group is famous as the Leo Triplet - a gathering of three magnificent galaxies in one field of view. Crowd pleasers when imaged with even modest telescopes, these galaxies can be introduced individually as NGC 3628 (top), M66 (bottom left), and M65 (bottom right). All three are large spiral galaxies. They tend to look dissimilar because their galactic disks are tilted at different angles to our line of sight. NGC 3628 is seen edge-on, with obscuring dust lanes cutting across the plane of the galaxy, while the disks of M66 and M65 are both inclined enough to show off their spiral structure. Gravitational interactions between galaxies in the group have also left telltale signs, including the warped and inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous deep view of the region spans about one degree (two full moons) on the sky. The field covers over 500 thousand light-years at the trio's estimated distance of 30 million light-years.
Credit & Copyright: Daniel Verschatse (Antilhue Observatory) -
Astronomy Picture of the Day
2006 March 10
Enceladus and the Search for Water
Explanation: Based on data from Cassini spacecraft instruments, researchers are now arguing that liquid water reservoirs exist only tens of meters below the surface of Saturn's small (500 kilometer diameter) but active moon Enceladus. The exciting new results center around towering jets and plumes of material erupting from the moon's surface. The plumes originate in the long tiger stripe fractures of the south polar region pictured here. Detailed models suport conclusions that the plumes arise from near-surface pockets of liquid water at temperatures of 273 kelvins (0 degrees Celsius), even though Enceladus has a surface temperature of about 73 kelvins (-200 degrees Celsius). Clearly an important step in the search for water and the potential for the origin of life beyond planet Earth, such near-surface reservoirs of water would be far more accessible than, for example, the internal ocean detected on the Jovian moon Europa.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA -
Astronomy Picture of the Day
2006 March 11
Colors of Comet Pojmanski
Explanation: Comet Pojmanski flew by planet Earth last weekend on a surprise trip through the inner solar system. Then an easy binocular target for morning skygazers, Pojmanski ultimately showed off a long tail, but it also presented some lovely green-blue hues as gas molecules in its tenuous coma and tail fluoresced in the sunlight. Astronomers Adam Block and Jay GaBany recorded this colorful high-resolution view on March 3rd in the darkness just before twilight. The picture spans about one full moon on the sky. Comet Pojmanski (C/2006 A1) is outward bound and fading now, still visible in binoculars for northern hemisphere observers.
Credit & Copyright: Adam Block (Caelum Observatory), R. Jay GaBany (Cosmotography.com)
