Astronomy fanatica
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Astronomy Picture of the Day
2005 November 7
NGC 7635: The Bubble Nebula
Explanation: It's the bubble versus the cloud. NGC 7635, the Bubble Nebula, is being pushed out by the stellar wind of massive central star BD+602522. Next door, though, lives a giant molecular cloud, visible above to the lower right. At this place in space, an irresistible force meets an immovable object in an interesting way. The cloud is able to contain the expansion of the bubble gas, but gets blasted by the hot radiation from the bubble's central star. The radiation heats up dense regions of the molecular cloud causing it to glow. The Bubble Nebula, pictured above in scientifically mapped colors to bring up contrast, is about 10 light-years across and part of a much larger complex of stars and shells. The Bubble Nebula can be seen with a small telescope towards the constellation of Cassiopeia.
Credit & Copyright: Russell Croman -
Astronomy Picture of the Day
2005 November 8
The Drifts of Mars
Explanation: What would it be like to walk across Mars? The robot Opportunity rover is currently experiencing what it is like to roll across part of the red planet. It's not always easy -- the rover is being instructed to dodge the deeper drifts of dark sand. During its exploration of Erebus Crater, the rover stopped and took the above picture. Inside this part of Erebus Crater, the surface of mars is covered not only by dark sand but also light outcrops of rock. Scattered across the exposed rock are numerous small round pebbles known as blueberries . Typically smaller than marbles, these unexpected and unusual rocks likely formed by accretion in an ancient wet environment. Also visible are some strange protruding edges known as razorbacks. The above image was taken early last month.
Credit : Mars Exploration Rover Mission, Cornell, JPL, NASA -
Astronomy Picture of the Day
2005 November 9
A Solar Prominence from SOHO
Explanation: What happened to the Sun? Nothing very unusual: the strange-looking solar appendage on the lower left is actually just a spectacular looking version of a common solar prominence. A solar prominence is a cloud of solar gas held above the Sun's surface by the Sun's magnetic field. Pictured above in 2002 October, NASA's Sun-orbiting SOHO spacecraft imaged an impressively large prominence hovering over the surface, informally dubbed a flame. Over 40 Earths could line up along the vast length of the fireless flame of hovering hot gas. A quiescent prominence typically lasts about a month, and may erupt in a Coronal Mass Ejection (CME) expelling hot gas into the Solar System. Although somehow related to the Sun's changing magnetic field, the energy mechanism that creates and sustains a Solar prominence is still a topic of research.
Credit : SOHO - EIT Consortium, ESA, NASA -
Astronomy Picture of the Day
2005 November 10
Gravitational Tractor
Explanation: How would you change the course of an Earth-threatening asteroid? One idea - a massive spacecraft that uses gravity as a towline - is illustrated in this dramatic artist's view of a gravitational tractor in action. In the hypothetical scenario worked out by Edward Lu and Stanley Love at NASA's Johnson Space Center, a 20 ton nuclear-electric spacecraft tows a 200 meter diameter asteroid by simply hovering near the asteroid. The spacecraft's ion drive thrusters are canted away from the surface. The steady thrust would gradually and predictably alter the course of the tug and asteroid, coupled by their mutual gravitational attraction. While it sounds like the stuff of science fiction, ion drives do power existing spacecraft and a gravitational tractor would work regardless of the asteroid's structure or surface properties.
Illustration Credit & Copyright: Dan Durda (FIAAA, B612 Foundation) -
Astronomy Picture of the Day
2005 November 11
Mountains of Creation
Explanation: This fantastic skyscape lies at the eastern edge of giant stellar nursery W5, about 7,000 light-years away in the constellation Cassiopeia. An infrared view from the Spitzer Space Telescope, it features interstellar clouds of cold gas and dust sculpted by winds and radiation from a hot, massive star outside the picture (just above and to the right). Still swaddled within the cosmic clouds, newborn stars are revealed by Spitzer's penetrating gaze, their formation also triggered by the massive star. Fittingly dubbed "Mountains of Creation", these interstellar clouds are about 10 times the size of the analogous Pillars of Creation in M16, made famous in a 1995 Hubble Space Telescope view. W5 is also known as IC 1848 and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae. The Spitzer image spans about 70 light-years at the distance of W5.
Credit: Lori Allen (Harvard-Smithsonian CfA) et al., JPL-Caltech, NASA -
Astronomy Picture of the Day
2005 November 12
Surveyor Hops
Explanation: This panorama of the cratered lunar surface was constructed from images returned by the US Surveyor 6 lander. Surveyor 6 was not the first spacecraft to accomplish a soft landing on the Moon ... but it was the first to land and then lift off again! After the spacecraft touched down near the center of the Moon's nearside in November of 1967, NASA controllers commanded it to hop. Briefly firing its rocket engine and lifting itself some 4 meters above the surface, the Surveyor moved about 2.5 meters to one side before setting down again. The hopping success of Surveyor 6 essentially marked the completion of the Surveyor series main mission - to determine if the lunar terrain was safe for the planned Apollo landings.
Credit: Surveyor Project, NASA -
Astronomy Picture of the Day
2005 November 13
Lunation
Explanation: Our Moon's appearance changes nightly. This time-lapse sequence shows what our Moon looks like during a lunation, a complete lunar cycle. As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible. The Moon always keeps the same face toward the Earth. The Moon's apparent size changes slightly, though, and a slight wobble called a libration is discernable as it progresses along its elliptical orbit. During the cycle, sunlight reflects from the Moon at different angles, and so illuminates different features differently. A full lunation takes about 29.5 days, just under a month (moon-th).
Credit & Copyright: Ant�nio Cidadƒo -
Astronomy Picture of the Day
2005 November 14
Everest Panorama from Mars
Click on above for image.
Explanation: If you could stand on Mars -- what might you see? Scroll right to find out. The robotic Spirit rover currently rolling across Mars climbed to the top of hill and took a series of images that were digitally combined into a 360 degree panorama over three days early last month. Spirit was instructed to take images having the same resolution as a human with 20-20 eyesight. The full panoramic result can be found by clicking on the above image and has a level of detail unparalleled in the history of Martian surface photography. The panorama was taken from the pinnacle of Husband Hill and has been dubbed the Everest panorama, in honor of the view from the tallest mountain on Earth. Visible in Gusev Crater are rocks, rusting sand, a Martian sundial, vast plains, nearby peaks, faraway peaks, and sand drifts. In the distance, fast moving dust devils can be seen as slight apparitions of red, green, or blue, the colors of filters used to build up this natural color vista.
Credit: Mars Exploration Rover Mission, Cornell, JPL, NASA -
Astronomy Picture of the Day
2005 November 15
A Taurid Meteor Fireball
Explanation: Have you ever seen a very bright meteor? Unexpected, this year's Taurid meteor shower resulted in numerous reports of very bright fireballs during the nights surrounding Halloween. Pictured above, a fireball that momentarily rivaled the brightness of the full Moon was caught over Cerro Pachon, Chile by a continuous sky monitor on November 1. Several bright Taurid fireballs are identifiable on the sky movie for that night. The above image is a digitally rectangled version of a circular fisheye frame and shows the entire sky, horizon to horizon. The bright meteor was seen swooping between the directions of the Large and Small Magellanic Clouds. The band of the Milky Way Galaxy crosses the horizon behind the dome of the 8-meter Gemini South Telescope. Taurid meteor fireballs are likely pebble sized debris left by Comet Encke. Over the next week the Leonids meteor shower will peak, although they will need to be seen through the glare of a nearly full Moon.
Credit: Lior Shamir (Michigan Tech), Cerro Pachon CONCAM, Night Sky Live Project -
Astronomy Picture of the Day
2005 November 16
A Robot's Shadow on Asteroid Itokawa
Explanation: What's that unusual looking spot on asteroid Itokawa? It's the shadow of the robot spacecraft Hayabusa that took the image. Japan's Hayabusa mission arrived at the asteroid in early September and has been imaging and maneuvering around the floating space mountain ever since. The above picture was taken earlier this month. Asteroid Itokawa spans about 300 meters. One scientific goal of the Hayabusa mission is to determine out how much ice, rock and trace elements reside on the asteroid's surface, which should give indications about how asteroids and planets formed in the early Solar System. A can-sized robot MINERVA that was scheduled to hop around the asteroid's surface has not, so far, functioned as hoped. Later this month, Hayabusa is scheduled to descend to asteroid Itokawa and collect surface samples in a return capsule. In December, Hayabusa will fire its rockets toward Earth and drop the return capsule down to Earth's Australian outback in 2007 June.
Credit & Copyright: ISIS, JAXA -
Astronomy Picture of the Day
2005 November 17
Young Stars of NGC 346
Explanation: Star cluster NGC 346 is embedded in the largest star forming region in the Small Magellanic Cloud, some 210,000 light-years distant. The massive stars of NGC 346 are short lived, but very energetic. Their winds and radiation sweep out an interstellar cavern in the gas and dust cloud about 200 light-years across, triggering star formation and sculpting the region's dense inner edge. Cataloged as N66, the star forming region also appears to contain a large population of infant stars. A mere 3 to 5 million years old and not yet burning hydrogen in their cores, the infant stars are strewn about the embedded star cluster. In the false-color Hubble Space Telescope image, visible and near-infrared light are seen as blue and green, while light from atomic hydrogen emission is red.
Credit: Antonella Nota (ESA/STScI) et al., ESA, NASA -
Astronomy Picture of the Day
2005 November 18
The 37 Cluster
Explanation: For the mostly harmless denizens of planet Earth, the brighter stars of open cluster NGC 2169 seem to form a cosmic 37. (Did you expect 42?.) Of course, the improbable numerical asterism appears solely by chance and lies at an estimated distance of 3,600 light-years toward the constellation Orion. As far as galactic or open star clusters go, NGC 2169 is a small one, spanning about 7 light-years. Formed at the same time from the same cloud of dust and gas, the stars of NGC 2169 are only about 8 million years old. Such clusters are expected to disperse over time as they encounter other stars, interstellar clouds, and experience gravitational tides while traveling through the galaxy. Over four billion years ago, our own Sun was likely formed in a similar open cluster of stars.
Credit & Copyright: Noel Carboni -
Astronomy Picture of the Day
2005 November 19
NGC 2359: Thor's Helmet
Explanation: NGC 2359 is a striking emission nebula with an impressive popular name - Thor's Helmet. Sure, its suggestive winged appearance might lead some to refer to it as the "duck nebula", but if you were a nebula which name would you choose? By any name NGC 2359 is a bubble-like nebula some 30 light-years across, blown by energetic winds from an extremely hot star seen near the center and classified as a Wolf-Rayet star. Wolf-Rayet stars are rare massive blue giants which develop stellar winds with speeds of millions of kilometers per hour. Interactions with a nearby large molecular cloud are thought to have contributed to this nebula's more complex shape and curved bow-shock structures. NGC 2359 is about 15,000 light-years distant toward the constellation Canis Major.
Credit: Christine and David Smith, Steve Mandel, Adam Block (KPNO Visitor Program), NOAO, AURA, NSF -
Astronomy Picture of the Day
2005 November 20
Rays from an Unexpected Aurora
Explanation: This aurora was a bit of a surprise. For starters, on this Friday morning in August 2002, no intense auroral activity was expected at all. Possibly more surprising, however, the aurora appeared to show an usual structure of green rays from some locations. In the above image, captured from North Dakota, USA, a picket fence of green rays stretches toward the horizon. Mirroring the green rays is a red band, somewhat rare in its own right. Lights from the cities of Bismarck and Mandan are visible near the horizon. Large sunspot groups indicate that activity from an active Sun is relatively likely, possibly causing other streams of energetic particles to cascade onto the Earth and so causing more auroras.
Credit & Copyright: Lyndon Anderson (Prairie Journal) -
Astronomy Picture of the Day
2005 November 21
The Missing Craters of Asteroid Itokawa
Explanation: Where are the craters on asteroid Itokawa? No one knows. The Japanese robot probe Hayabusa recently approached the Earth-crossing asteroid and is returning pictures showing a surface unlike any other Solar System body yet photographed -- a surface possibly devoid of craters. One possibility for the lack of common circular indentations is that asteroid Itokawa is a rubble pile -- a bunch of rocks and ice chunks only loosely held together by a small amount of gravity. If so, craters might be filled in whenever the asteroid gets jiggled by a passing planet -- Earth in this case. Alternatively, surface particles may become electrically charged by the Sun, levitate in the microgravity field, and move to fill in craters. Over the weekend, Hayabusa lowered itself to the surface of the strange asteroid in an effort to study the unusual body and collect surface samples that could be returned to Earth in 2007.
Credit & Copyright: ISAS, JAXA -
Astronomy Picture of the Day
2005 November 22
Galactic Collision in Cluster Abell 1185
Explanation: What is a guitar doing in a cluster of galaxies? Colliding. Clusters of galaxies are sometimes packed so tight that the galaxies that compose them collide. A prominent example occurs on the left of the above image of the rich cluster of galaxies Abell 1185. There at least two galaxies, cataloged as Arp 105 and dubbed The Guitar for their familiar appearance, are pulling each other apart gravitationally. Most of Abell 1185's hundreds of galaxies are elliptical galaxies, although spiral, lenticular, and irregular galaxies are all clearly evident. Many of the spots on the above image are fully galaxies themselves containing billions of stars, but some spots are foreground stars in our own Milky Way Galaxy. Recent observations of Abell 1185 have found unusual globular clusters of stars that appear to belong only to the galaxy cluster and not to any individual galaxy. Abell 1185 spans about one million light years and lies 400 million light years distant.
Credit & Copyright: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT -
Astronomy Picture of the Day
2005 November 23
Pandora: A Shepherd Moon of Saturn
Explanation: What does Saturn's small moon Pandora look like? To help find out, the robot Cassini spacecraft now orbiting Saturn passed about 50,000 kilometers from the unusual moon in early September. The highest resolution image of Pandora ever taken was then captured and is shown above in representative colors. Features as small as 300 meters can be discerned on 80-kilometer wide Pandora. Craters on Pandora appear to be covered over by some sort of material, providing a more smooth appearance than sponge-like Hyperion, another small moon of Saturn. Curious grooves and ridges also appear to cross the surface of the small moon. Pandora is partly interesting because, along with its companion moon Prometheus, it helps shepherd the particles of Saturn's F ring into a distinct ring.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA -
Astronomy Picture of the Day
2005 November 24
Dusty NGC 1333
Explanation: Dusty NGC 1333 is seen as a reflection nebula in visible light images, sporting bluish hues characteristic of starlight reflected by dust. But at longer infrared wavelengths, the interstellar dust itself glows - shown in red in this false-color Spitzer Space Telescope image. The penetrating infrared view also shows youthful stars that would otherwise still be obscured by the dusty clouds which formed them. Notably, greenish streaks and splotches that seem to litter the region trace the glow of cosmic jets blasting away from emerging young stellar objects as the jets plow into the cold cloud material. In all, the chaotic scene likely resembles one in which our own Sun formed over 4.5 billion years ago. NGC 1300 is a mere 1,000 light-years distant in the constellation Perseus.
Credit: R. A. Gutermuth (Harvard-Smithsonian CfA) et al. JPL-Caltech, NASA -
Astronomy Picture of the Day
2005 November 25
Moon Over Antarctica
Explanation: Last week, the nearly Full Moon set along the northern horizion - as seen from Davis Station, Antarctica. The squashed orange pumpkin shape just silhouettes the peak of a distant iceberg in this stunning view. The Moon's apparently squashed shape is due to atmospheric bending of light or refraction -- an effect which is more severe closer to the horizon. Skimming low along the stark features of the frozen landscape, the Moon's lower edge appears noticeably more distorted than the upper limb. Along with about 70 others present at Davis Station, Dr. Jim Behrens had a chance to enjoy the view while studying the ongoing detachment of a large iceberg known as "Loose Tooth".
Credit & Copyright: James Behrens (IGPP, Scripps Institution of Oceanography) -
Astronomy Picture of the Day
2005 November 26
A Stereo Sun
Explanation: A stereo view of the closest star, this creatively composited image was constructed from an extensive archive of pictures taken between March 2004 and April 2005. When viewed with red/blue glasses, the Sun's disk and surface features, including sunspots, filaments, and prominences, stand out in an exaggerated stereo perspective. The images were recorded through a narrow band hydrogen-alpha filter, designed to transmit only light from hydrogen atoms in the solar atmosphere. After combining the solar hydrogen-alpha images, a 3D star field was added to the final anaglyphic stereo view.
Credit & Copyright: Greg Piepol -
Astronomy Picture of the Day
2005 November 27
Light Echoes from V838 Mon
Explanation: What caused this outburst of V838 Mon? For reasons unknown, star V838 Mon's outer surface suddenly greatly expanded with the result that it became the brightest star in the entire Milky Way Galaxy in January 2002. Then, just as suddenly, it faded. A stellar flash like this has never been seen before -- supernovas and novas expel matter out into space. Although the V838 Mon flash appears to expel material into space, what is seen in the above image from the Hubble Space Telescope is actually an outwardly moving light echo of the bright flash. In a light echo, light from the flash is reflected by successively more distant rings in the complex array of ambient interstellar dust that already surrounded the star. V838 Mon lies about 20,000 light years away toward the constellation of the unicorn (Monoceros), while the light echo above spans about six light years in diameter.
Credit: NASA and the Hubble Heritage Team (AURA/STScI) -
Astronomy Picture of the Day
2005 November 28
Vista Inside Gusev Crater on Mars
Explanation: What is the geologic history of Mars? To help find out, the robot Spirit rover explored the terrain on the way up to the top of Husband Hill and took pictures along the way. Earth-bound team members later combined images from one camera with colors from another to create this semi-realistic vista from near the top of the rugged hill. Many rock faces were imaged and probed along the way. The above image captures not only a high and distant Mars inside Gusev crater, but also more of the refrigerator-sized Spirit rover than other similar vistas. Visible technology includes a wide array of energy-absorbing solar panels, a sundial, and the circular high gain communications antenna.
Credit: Marco Di Lorenzo et al. courtesy Aviation Week, Mars Exploration Rover Mission, Cornell, JPL, NASA;
Courtesy M. Di Lorenzo et al. & Aviation Week -
Astronomy Picture of the Day
2005 November 29
Simeis 147: Supernova Remnant from Palomar
Explanation: It's easy to get lost following the intricate filaments in this detailed image of faint supernova remnant Simeis 147. Seen towards the constellation Taurus it covers nearly 3 degrees (6 full moons) on the sky corresponding to a width of 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. The above image is a color composite of 66 blue and red color band images from the National Geographic Palomar Observatory Sky Survey taken with the wide field Samuel Oschin 48-inch Telescope. The area of the sky shown covers over 70 times the area of the full Moon. This supernova remnant has an apparent age of about 100,000 years - meaning light from the massive stellar explosion first reached Earth 100,000 years ago - but this expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star's core.
Credit: Digitized Sky Survey, ESA/ESO/NASA FITS Liberator
Color Composite: Davide De Martin (Skyfactory) -
Astronomy Picture of the Day
2005 November 30
Reflections on the Horsehead Nebula
Explanation: Sculpted by stellar winds and radiation, a magnificent interstellar dust cloud by chance has assumed this recognizable shape. Fittingly named the Horsehead Nebula, it is some 1,500 light-years distant, embedded in the vast Orion cloud complex. About five light-years "tall", the dark cloud is cataloged as Barnard 33 and is visible only because its obscuring dust is silhouetted against the glowing red emission nebula IC 434. Contrasting blue reflection nebula NGC 2023 is visible on the lower left. In this gorgeous color image, both Horsehead and NGC 2023 seem to be caught in beams of light shining from above -- but the beams are actually just internal reflections from bright star Sigma Orionis, just off the upper edge of the view.
Credit & Copyright: Daniel Verschatse (Antilhue Observatory) -
Astronomy Picture of the Day
2005 December 1
SOHO's Uninterrupted View of the Sun
Explanation: Launched ten years ago this week, SOHO (the SOlar and Heliospheric Observatory) still enjoys an uninterrupted view of the Sun. Twelve sungazing instruments on board the spacecraft have explored the Sun's internal structure, the extensive solar atmosphere and solar wind, and discovered over 1,000 comets from a remarkable orbit around a point about 1.5 million kilometers directly sunward of planet Earth itself. At that location, known as a Lagrange point, the gravitational influence of the Earth and Sun are equal. With scientific instrument teams distributed around the world, the SOHO operations center is located at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Mission operations are planned through March of 2007 to allow the study of a complete 11-year solar cycle. Contributions from SOHO's instruments are represented in the colorful montage image. Happy tenth anniversary SOHO!
Credit: SOHO Consortium, ESA, NASA
Image Montage: Steele Hill (GSFC)
