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 1

A Soyuz Spacecraft Approaches the Space Station

Explanation: Last month, a Soyuz TMA-7 spacecraft docked with the International Space Station. The spacecraft was launched a few days earlier from the Baikonur Cosmodrome in Kazakhstan. Pictured above, the approaching Soyuz spacecraft carried the new Expedition 12 crew to the Earth-orbiting International Space Station (ISS), as well as fee-paying spaceflight participant. The Expedition 12 crew is expected to stay on the ISS for about six months, while replacing the Expedition 11 crew who had been on the station for about six months themselves. About a week after this image was taken, the Expedition 11 crew returned to Earth in the Soyuz capsule, along with the spaceflight participant. The Expedition 12 crew will carry out repairs on the ISS, explore new methods of living in space, and conduct research in space including a kidney stone experiment.

Credit : ISS Expedition 11 Crew, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 November 2

Epimetheus and Janus: Interchangeable Moons of Saturn

Explanation: These two moons change places. Epimetheus and Janus, two small moons of Saturn, actually switch positions as they orbit their home planet. The orbital radii of the moons are strangely separated by less than the radii of the moons themselves: about 50 kilometers. One moon orbits Saturn well ahead of the other, at first. As the two moons gravitationally attract, they approach each other and, every few years, actually pass and trade orbits. This strange dance creates speculation that Epimetheus and Janus were once joined and later split from each other. Pictured above, the two moons were photographed rounding their orbits just outside of Saturn's F ring. The above image was taken in early September by the robot Cassini spacecraft, also orbiting Saturn.

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

poon cho tang SG

Astronomy Picture of the Day

2005 November 3

Possible Pluto Moons

Explanation: In 1930, tiny, icy world Pluto was discovered orbiting in the distant solar system. In 1978, its relatively large companion Charon was detected by ground-based observations. This year, the Hubble Space Telescope may well have detected two further members of the Pluto system. Provisionally designated S/2005 P1 and S/2005 P2, the two potential new moons are seen orbiting in a counterclockwise direction about 44,000 kilometers (27,000 miles) from Pluto in these deep Hubble images recorded only three days apart. The diminutive and faint companions are also apparently detected on Hubble images of Pluto from 2002, but this coming February follow-up observations are planned in an effort to confirm the discovery of the new moons. Compared to Pluto's and Charon's diameters of 2,300 and 1,300 kilometers respectively, these moons are estimated to be between 60 and 200 kilometers across. Well within the Kuiper Belt, an extensive region beyond the orbit of Neptune, the Pluto system could be the first quadruple Kuiper Belt object known.

Credit : H. Weaver (JHU / APL), A. Stern (SwRI), and the HST Pluto Companion Search Team, ESA, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 November 4

M78: Stardust and Starlight

Explanation: Interstellar dust clouds and bright nebulae abound in the fertile constellation of Orion. One of the brightest, M78, is just below center in this sharp widefield view, covering an area north of Orion's belt. At a distance of about 1,500 light-years, the bluish nebula itself is about 5 light-years across. Its blue tint is due to dust preferentially reflecting the blue light of hot, young stars in the region. Dark dust lanes and other nebulae can easily be traced through this gorgeous skyscape that also includes the remarkable McNeil's Nebula -- a newly recognized nebula associated with the formation of a sun-like star.

Credit & Copyright: Stephan Messner

poon cho tang SG

Astronomy Picture of the Day

2005 November 5

Aurora from Space

Explanation: From the ground, spectacular auroras seem to dance high above. But the International Space Station (ISS) orbits at nearly the same height as many auroras, sometimes passing over them, and sometimes right through them. Still, the auroral electron and proton streams pose no direct danger to the ISS. In 2003, ISS Science Officer Don Pettit captured the green aurora, pictured above in a digitally sharpened image. From orbit, Pettit reported that changing auroras appeared to crawl around like giant green amoebas. Over 300 kilometers below, the Manicouagan Impact Crater can be seen in northern Canada, planet Earth.

Credit: Don Pettit, ISS Expedition 6, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 November 6

A Sunspot Up Close

Explanation: Why would a small part of the Sun appear slightly dark? Visible above is a close-up picture of a sunspot, a depression on the Sun's face that is slightly cooler and less luminous than the rest of the Sun. The Sun's complex magnetic field creates this cool region by inhibiting hot material from entering the spot. Sunspots can be larger than the Earth and typically last for only a few days. This high-resolution picture also shows clearly that the Sun's face is a bubbling sea of separate cells of hot gas. These cells are known as granules. A solar granule is about 1,000 kilometers across and lasts about 10 minutes. After that, many granules end up exploding.

Credit : Vacuum Tower Telescope, NSO, NOAO

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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)

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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: Antnio Cidado

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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

poon cho tang SG

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)

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