Astronomy fanatica

last SG · 2005-02-27T00:18:37+00:00

u'll find it on page 4 of this thread

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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)

poon cho tang SG

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

poon cho tang SG

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)

poon cho tang SG

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

poon cho tang SG

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)

poon cho tang SG

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)

poon cho tang SG

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)

poon cho tang SG

Astronomy Picture of the Day

2005 December 2

Crab Nebula Mosaic from HST

Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the cosmic Crab is now known to be a supernova remnant, an expanding cloud of debris from the death explosion of a massive star. Light from that stellar catastrophe was first witnessed by astronomers on planet Earth in the year 1054. Composed of 24 exposures taken in October 1999, January 2000, and December 2000, this Hubble Space Telescope mosaic spans about six light years. Colors in the intricate filaments trace the light emitted from atoms of hydrogen, oxygen, and sulfur in the debris cloud. The erie blue interior glow is emitted by high-energy electrons accelerated by the Crab's central pulsar. One of the most exotic objects known to modern astronomers, the pulsar is a neutron star, the spinning remnant of the collapsed stellar core. The Crab Nebula lies about 6,500 light-years away in the constellation Taurus.

Image Credit: NASA, ESA, J. Hester, A. Loll (ASU)
Acknowledgement: Davide De Martin (Skyfactory)

poon cho tang SG

Astronomy Picture of the Day

2005 December 3

Astro 1 In Orbit

Explanation: Fifteen years ago, in December of 1990, the Space Shuttle Orbiter Columbia carried an array of astronomical telescopes high above the Earth's obscuring atmosphere to explore the Universe at ultraviolet and x-ray wavelengths. The telescopes, known by the acronyms UIT, HUT, WUPPE, and BBXRT, are seen here in Columbia's payload bay against a spectacular view of the constellation Orion. The ultraviolet telescopes were mounted on a common structure - HUT is visible in this view along with a star tracker (the silver cone at the left). Taken during the nighttime portion of the shuttle's 90 minute orbit, the picture shows the telescopes and structures illuminated by moonlight.

Credit: STS-35 Crew, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 December 4

Proxima Centauri: The Closest Star

Explanation: What is the closest star to our Sun? It is Proxima Centauri, the nearest member of the Alpha Centauri triple star system. Light takes only 4.22 years to reach us from Proxima Centauri. This small red star, captured in the center of the above image, is so faint that it was only discovered in 1915 and is only visible through a telescope. Stars of all types from our Milky Way Galaxy are visible in the background. The brightest star in the Alpha Centauri system is quite similar to our Sun, has been known as long as recorded history, and is the third brightest star in the night sky. The Alpha Centauri system is primarily visible from Earth's Southern Hemisphere.

Credit & Copyright: David Malin, UK Schmidt Telescope, DSS, AAO

poon cho tang SG

Astronomy Picture of the Day

2005 December 5

Fountains Discovered on Saturn's Enceladus

Explanation: Fountains of ice shoot out from Saturn's moon Enceladus. Clear discovery images of the fountains were made using observations from the robot Cassini spacecraft currently orbiting Saturn. During a recent pass, Cassini was programmed to look back toward the Sun where Enceladus would appear as a thin crescent. From this vantage point, particles emitted from the surface would better show themselves by reflecting sunlight. The tactic was successful -- the above frame shows several plumes emanating from regions previously known to contain gashes in the surface dubbed tiger stripes. Cassini detected an increase in particle emissions from these regions during a July flyby. Some of these ice particles likely contribute to the make up of Saturn's mysterious E ring.

Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 December 6

The Veil Nebula Unveiled

Explanation: These wisps of gas are all that remain visible of a Milky Way star. Many thousands of years ago that star exploded in a supernova leaving the Veil Nebula, pictured above. At the time, the expanding cloud was likely as bright as a crescent Moon toward the constellation of Cygnus, visible for weeks to people living at the dawn of recorded history. The supernova remnant lies about 1400 light-years away and covers over five times the size of the full Moon. The above image of the Veil was made clearer by digitally dimming stars in the frame. The bright wisp at the top is known as the Witch's Broom Nebula and can be seen with a small telescope. The Veil Nebula is also known as the Cygnus Loop.

Credit & Copyright: Mikael Svalgaard

poon cho tang SG

Astronomy Picture of the Day

2005 December 7

Europe at Night

Explanation: Can you find your favorite European city? The above digital fantasy of Europe at Night is a digital composite of archived satellite images taken both during the day and night. This image is different from what an astronaut would see for reasons including a complete lack of clouds and an unrealistic exaggeration of lights and contrasts. Even so, the geography underlying the image is captivating. Nighttime light patterns have been accumulated from the USAF Defense Meteorological Satellite Program (DMSP) Operational Linescan System.

Illustration Credit & Copyright: Planetary Visions Ltd.; Courtesy: Kevin M. Tildsley

poon cho tang SG

Astronomy Picture of the Day

2005 December 8

X-Rays from the Perseus Cluster Core

Explanation: The Perseus Cluster of thousands of galaxies, 250 million light-years distant, is one of the most massive objects in the Universe and the brightest galaxy cluster in the x-ray sky. At its core lies the giant cannibal galaxy Perseus A (NGC 1275), accreting matter as gas and galaxies fall into it. This deep Chandra Observatory x-ray image spans about 300,000 light-years across the galaxy cluster core. It shows remarkable details of x-ray emission from the monster galaxy and surrounding hot (30-70 million degrees C) cluster gas. The bright central source is the supermassive black hole at the core of Perseus A itself. Low density regions are seen as dark bubbles or voids, believed to be generated by cyclic outbursts of activity from the central black hole. The activity creates pressure waves - sound waves on a cosmic scale- that ripple through the x-ray hot gas. Dramatically, the blue-green wisps just above centre in the false-color view are likely x-ray shadows of the remains of a small galaxy falling into the burgeoning Perseus A.

Credit: A. Fabian (IoA Cambridge) et al., NASA

poon cho tang SG

Astronomy Picture of the Day

2005 December 9

December Moon Meets Evening Star

Explanation: If you've been outdoors near sunset, then you've probably noticed Venus low in the west as the brilliant evening star. Sometimes mistaken for a tower light near the horizon, Venus is the third brightest celestial beacon, after the Sun and Moon, in planet Earth's sky. That distinction is particularly easy to appreciate in this peaceful scene featuring the crescent Moon, Venus, and sunset colors captured on December 4th near Albany, Missouri, USA. As this season's evening star, Venus will be at its most brilliant tonight, but as December progresses the bright planet will begin to fall out of the western sky. By early next week, December's Moon will have moved on to meet another bright planet overhead -- Mars.

Credit & Copyright: Dan Bush (Missouri Skies)

poon cho tang SG

Astronomy Picture of the Day

2005 December 10

The Last Moon Shot

Explanation: In 1865 Jules Verne predicted the invention of a space capsule that could carry people. His science fiction story "From the Earth to the Moon" outlined his vision of a cannon in Florida so powerful that it could shoot a Projectile-Vehicle carrying three adventurers to the Moon. Over 100 years later NASA, guided by Wernher Von Braun's vision, produced the Saturn V rocket. From a spaceport in Florida, this rocket turned Verne's fiction into fact, launching 9 Apollo Lunar missions and allowing 12 astronauts to walk on the Moon. As spotlights play on the rocket and launch pad at dusk, the last moon shot, Apollo 17, is pictured here awaiting its December 1972 night launch.

Credit: Apollo Program, NASA (image scanned by J.L. Pickering)

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