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 October 12

Cratered Cliffs of Ice on Saturn's Tethys

Explanation: The surface of Saturn's moon Tethys is riddled with icy cliffs and craters. The most detailed images ever taken of Tethys were captured late last month as the robot Cassini spacecraft swooped past the frozen ice moon. The above image was taken from about 32,000 kilometers distant and shows a jagged landscape of long cliffs covered with craters. At the bottom of many craters appears some sort of unknown light-colored substance, in contrast to the unknown dark substance that appears at the bottom of Saturn's moon Hyperion. Tethys is one of the larger moons of Saturn, spanning about 1,000 kilometers across. The density of Tethys indicates a composition almost entirely of water ice. Tethys is thought to have been predominantly liquid sometime in its distant past, creating some of its long ice-cliffs as it cracked during freezing.

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

poon cho tang SG

Astronomy Picture of the Day

2005 October 13

Alnitak, Alnilam, Mintaka

Explanation: Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (left to right) along the diagonal in this gorgeous cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun. They lie about 1,500 light-years away, born of Orion's well-studied interstellar clouds. In fact, clouds of gas and dust adrift in this region have intriguing and some surprisingly familiar shapes, including the dark Horsehead Nebula and Flame Nebula near Alnitak at the lower left. The famous Orion Nebula itself lies off the bottom of this star field that covers an impressive 4.4x3.5 degrees on the sky. The color picture was composited from digitized black and white photographic plates recorded through red and blue astronomical filters, with a computer synthesized green channel. The plates were taken using the Samuel Oschin Telescope, a wide-field survey instrument at Palomar Observatory, between 1987 and 1991.

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 October 14

Eclipse Shirt

Explanation: Of course, everyone is concerned about what to wear to a solar eclipse. No need to worry though, nature often conspires to project images of the eclipse so that stylish and appropriate patterns adorn many visible surfaces - including clothing - at just the right time. Most commonly, small gaps between leaves on trees can act as pinhole cameras and generate multiple recognizable images of the eclipse. But while in Madrid to view the October 3rd annular eclipse of the Sun, astronomer Philippe Haake met a friend who had another inspiration. The result, a grid of small holes in a kitchen strainer produced this pattern of images on an 'eclipse shirt'.

Credit & Copyright: Philippe Haake

poon cho tang SG

Astronomy Picture of the Day

2005 October 15

Dusty Environs of Eta Carinae

Explanation: Eta Car is a massive star, but it's not as bright as it used to be. Now only easily visible in binoculars or a small telescope, Eta Carinae has a history of spectacular flaring and fading behavior. In fact, in April of 1843 Eta Car briefly became second only to Sirius as the brightest star in planet Earth's night sky, even though at a distance of about 7,500 light-years, it is about 800 times farther away. Surrounded by a complex and evolving nebula, Eta Carinae is seen near the center of this false-color infrared image, constructed using data from the Midcourse Space Experiment (MSX). The MSX satellite mapped the galactic plane in 1996. In the picture, wispy, convoluted filaments are clouds of dust glowing at infrared wavelengths. Astronomers hypothesize that Eta Car itself will explode as a supernova in the next million years or so. Massive Eta Car has even been considered a candidate for a hypernova explosion and the potential source of a future gamma-ray burst.

Credit: MSX, IPAC, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 October 16

Astronomy Quilt of the Week

Explanation: Demonstrating her mastery of a traditional astronomical imaging technique quilter and astronomy enthusiast Judy Ross has produced this spectacular composition of "Astronomy Quilt Piece of the Week". Her year-long effort resulted in an arrangement for a six by seven foot quilt consisting of 52 individual pieces (11 inches by 8 inches), one for each week, which she reports were inspired by her steady diet of APOD's daily offerings. Some of the pieces are based on actual pictures, such as the Hubble Space Telescope's view of planet forming AB Aurigae or Bill Keel's image of the nearby Pinwheel Galaxy. Others, with titles like the Blue Carpet Nebula and Duck Contemplates Black Hole, are from her own creative imaginings.

Credit & Copyright: Judy W. Ross, Point Roberts, WA

poon cho tang SG

Astronomy Picture of the Day

2005 October 17

Short Gamma-Ray Bursts Localized

Explanation: What causes gamma-ray bursts? The most energetic type of explosions known in the cosmos has been an enigma since discovered over 30 years ago. It now appears that there may not be one unique type of progenitor. Long duration gamma-ray bursts (GRBs) have been localized, over the past few years, to blue regions in the universe rich in star formation. Massive young stars nearing the end of their short lives commonly explode in these regions. Astronomers associate these long duration GRBs, that can last from seconds to minutes, with a type of stellar explosion common in young massive stars. Over the past few months, short duration GRBs have finally been localized and found to occur in different types of regions -- not only blue regions rich in star formation. Many astronomers therefore now theorize that short GRBs, which typically last less than one second, are the result of a different progenitor process than long GRBs. A leading model is that a short GRB will occur when a neutron star either impacts another neutron star or a black hole. Such collisions may occur well after star-forming regions have otherwise burned out. Pictured in the above illustration, two energized neutrons stars finally approach each other in their orbits, a death spiral that might end with a short GRB.

Illustration Credit: Dana Berry, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 October 18

AE Aurigae: The Flaming Star

Explanation: Is star AE Aurigae on fire? No. Even though AE Aurigae is named the flaming star, the surrounding nebula IC 405 is named the Flaming Star Nebula, and the region appears to harbor red smoke, there is no fire. Fire, typically defined as the rapid molecular acquisition of oxygen, happens only when sufficient oxygen is present and is not important in such high-energy, low-oxygen environments such as stars. The material that appears as smoke is mostly interstellar hydrogen, but does contain smoke-like dark filaments of carbon-rich dust grains. The bright star AE Aurigae, visible just below the image center, 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, as seen in the surrounding emission nebula. Pictured above, the Flaming Star nebula lies about 1,500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga).

Credit & Copyright: Thomas V. Davis (tvdavisastropix.com)

poon cho tang SG

Astronomy Picture of the Day

2005 October 19

On the Possibility of Ascending to Mars

Explanation: On another October 19, in 1899, a 17 year-old Robert Goddard climbed a cherry tree on a beautiful autumn afternoon in Worcester, Massachusetts. Inspired by H.G. Wells' War of the Worlds and gazing out across a meadow, young Goddard imagined it would be wonderful to make a device that had the possibility of ascending to Mars. Forever more he felt his life had a purpose and in the following years his diary entries record October 19th as "Anniversary Day", the anniversary of his ascent into the cherry tree. By 1926 he had designed, built, and flown the world's first liquid fuel rocket. Mars is just visible through the trees at the lower right in this dramatic sky view that also features the Moon and Venus -- all visited by liquid fuel rockets constructed on principles developed by Goddard.

Image Credit & Copyright: Fred Espenak ( www.MrEclipse.com)

poon cho tang SG

Astronomy Picture of the Day

2005 October 20

The Andromeda Galaxy in Infrared

Explanation: What is the Andromeda galaxy really like? To find out, astronomers looked at our largest galactic neighbor in a different light: infrared. Astronomers trained the orbiting Spitzer Space Telescope at the Messier monster (M31) for over 18 hours, creating a mosaic that incorporated 11,000 separate exposures. The result, pictured above, shows M31 in greater infrared detail than ever before. Infrared light in this 24-micron color band is particularly sensitive to dust heated up by stars. Visible above are previously undiscovered features including intricate structure in the spiral arms, a spiral arc near the center, an off center ring of star formation, and an unusual hole in the galaxy's disk. In contrast, the Andromeda galaxy appears much smoother in visible light and even ultraviolet light. Analyses and comparison of this image to other images will likely yield clues not only to the violent past of M31 but to our own Milky Way Galaxy as well.

Credit: K. Gordon (U. Arizona), JPL-Caltech, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 October 21

Ringside

Explanation: Orbiting in the plane of Saturn's rings, Dione and the other icy saturnian moons have a perpetual ringside view of the gorgeous gas giant planet. Of course, while passing through the ring plane the Cassini spacecraft also shares their stunning perspective. The rings themselves can be seen slicing across the bottom of this Cassini snapshot. Remarkably thin, the bright rings still cast arcing shadows across the planet's cloud tops. Pale Dione, in the foreground, is about 1,100 kilometers across and orbits over 300,000 kilometers from the visible outer edge of the A ring.

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

poon cho tang SG

Astronomy Picture of the Day

2005 October 22

Ring Galaxy AM 0644-741 from Hubble

Explanation: How could a galaxy become shaped like a ring? The rim of the blue galaxy pictured on the right is an immense ring-like structure 150,000 light years in diameter composed of newly formed, extremely bright, massive stars. That galaxy, AM 0644-741, is known as a ring galaxy and was caused by an immense galaxy collision. When galaxies collide, they pass through each other -- their individual stars rarely come into contact. The ring-like shape is the result of the gravitational disruption caused by an entire small intruder galaxy passing through a large one. When this happens, interstellar gas and dust become condensed, causing a wave of star formation to move out from the impact point like a ripple across the surface of a pond. The intruder galaxy has since moved out of the frame taken by the Hubble Space Telescope and released to commemorate the anniversary of Hubble's launch in 1990. Ring galaxy AM 0644-741 lies about 300 million light years away.

Credit : Hubble Heritage Team (AURA / STScI), J. Higdon (Cornell) ESA, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 October 23

At the Center of the Milky Way

Explanation: At the center of our Milky Way Galaxy lies a black hole with over 2 million times the mass of the Sun. Once a controversial claim, this astounding conclusion is now virtually inescapable and based on observations of stars orbiting very near the galactic center. Using one of the Paranal Observatory's very large telescopes and a sophisticated infrared camera, astronomers patiently followed the orbit of a particular star, designated S2, as it came within about 17 light-hours of the center of the Milky Way (about 3 times the radius of Pluto's orbit). Their results convincingly show that S2 is moving under the influence of the enormous gravity of an unseen object that must be extremely compact -- a supermassive black hole. This deep near-infrared image shows the crowded inner 2 light-years of the Milky Way with the exact position of the galactic center indicated by arrows. The ability to track stars so close to the galactic center can accurately measure the black hole's mass and perhaps even provide an unprecedented test of Einstein's theory of gravity as astronomers watch a star orbit a supermassive black hole.

Credit : Rainer Schödel (MPE) et al., NAOS-CONICA, ESO

poon cho tang SG

Astronomy Picture of the Day

2005 October 24

Angular Sand on Martian Hills

Explanation: Why isn't this sand round? The robotic Spirit rover currently rolling across Mars has found notably angular sand in the Columbia Hills on Mars. Previously, small bits of sand found in the plains of Gusev Crater were significantly more round. The finding indicates that angular hill sand has tumbled less and likely traveled a shorter distance than the corresponding round plain sand. Such tumbling has the general effect of making sand and rocks increasingly round and with fewer sharp edges. Pictured above, as taken last month, are angular sand grains magnified by Spirit's Microscopic Imager. The above frame spans about three centimeters.

Credit : Mars Exploration Rover Mission, JPL, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 October 25

Supernova Remnant N132D in Optical and X Rays

Explanation: Thousands of years after a star exploded, its expanding remnant still glows brightly across the spectrum. Such is the case with N132D, a supernova remnant located in the neighboring Large Magellanic Cloud (LMC) galaxy. The expanding shell from this explosion now spans 80 light-years and has swept up about 600 Suns worth of mass. N132D was imaged recently in optical light and in great detail with the Hubble Space Telescope. The Hubble image was then combined with a position coincident detailed image in X-ray light taken by the Chandra X-ray Observatory. The combination, shown above in representative colors, shows a nearly spherical expanding shockwave highlighted by pink emission from hydrogen gas and purple emission from oxygen gas. A dense field of unrelated stars also from the LMC populates the image. Studying the image gives an opportunity to study material once hidden deep inside a star. N132D spans about 150 light years and lies about 160,000 light years away toward the constellation of Dorado.

Credit : NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
Acknowledgment: J.C. Green (Univ. of Colorado) and the Cosmic Origins Spectrograph (COS) GTO team; NASA/CXO/SAO

poon cho tang SG

Astronomy Picture of the Day

2005 October 26

4,500 Kilometers Above Dione

Explanation: What does the surface of Saturn's moon Dione look like? To find out, the robot Cassini spacecraft currently orbiting Saturn flew right past the fourth largest moon of the giant planet earlier this month. Pictured above is an image taken about 4,500 kilometers above Dione's icy surface, spanning about 23 kilometers. Fractures, grooves, and craters in Dione's ice and rock are visible. In many cases, surface features are caused by unknown processes and can only be described. Many of the craters have bright walls but dark floors, indicating that fresher ice is brighter. Nearly parallel grooves run from the upper right to the lower left. Fractures sometimes across the bottom of craters, indicating a relatively recent formation. The lip of a 60-kilometer wide crater runs from the middle left to the upper center of the image, while the crater's center is visible on the lower right. Images like this will continue to be studied to better understand Dione as well as Saturn's complex system of rings and moons.

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

poon cho tang SG

Astronomy Picture of the Day

2005 October 27

The Last Titan

Explanation: On October 19th, a rocket blasted off from Vandengberg Air Force Base - the last Titan rocket. Carrying a payload for the US National Reconnaissance Office, the successful Titan IV B launch brings to a close the Titan program whose first launch was in 1959. Originally designed as an intercontinental ballistic missle, the Titan rocket ultimately evolved into a heavy lift workhorse, launching defense, commercial, and scientific payloads to Earth orbit and beyond. In fact, many historic space explorations began with Titan launches, including manned Gemini missions, the Viking missions to Mars, the Voyager tours of the outer solar system, and the Cassini spacecraft now orbiting Saturn. Cassini's probe Huygens accomplished the most distant landing on another world, while Voyager 1 is now humanity's most distant spacecraft.

Credit : Courtesy 30th Space Wing, Vandenberg Air Force Base

poon cho tang SG

Astronomy Picture of the Day

2005 October 28

October Mars

Explanation: This October, Mars has become a bright, yellowish star in planet Earth's sky as it approaches oppositon, the period when Mars and Earth pass close as they orbit the Sun. How close is Mars? A mere 70 million kilometers or so, close enough to allow Earth-bound astronomers excellent views of the alluring Red Planet. For example, this series of sharp Mars images follows the development of a dust storm as the planet rotates from right to left. The telescopic views clearly show details of the martian surface, including the planet's southern ice cap (top) and hood of clouds over the north pole at the bottom edge. The dust storm itself is visible as light yellowish band across an otherwise dark region in the southern hemisphere. Even if a telescope isn't handy, be sure to check out Mars soon. It will continue to shine brightly in the night over the coming days.

Credit & Copyright: Chris Cook

poon cho tang SG

Astronomy Picture of the Day

2005 October 29

NGC 3242: The Ghost of Jupiter

Explanation: After a star like the Sun completes fusion in its core, it throws off its outer layers in a brief, beautiful cosmic display called a planetary nebula. NGC 3242 is such a planetary nebula, with the stellar remnant white dwarf star visible at the center. This nebula is sometimes called The Ghost of Jupiter for its faint, but similar appearance to our solar system's ruling gas giant planet. NGC 3242 is light-years across however, and much farther away than the measly 40 light-minutes distance to Jupiter. In fact, while watching this ghostly nebula expand over time, astronomers have estimated the distance to NGC 3242 to be about 1,400 light-years. The red FLIERs visible near the edges of the nebula are still a bit mysterious, though.

Credit: Bruce Balick (U. Washington) et al., HST, NASA

poon cho tang SG

Astronomy Picture of the Day

2005 October 30

A Dark and Stormy Night

Explanation: It was a dark and stormy night. But on 2003 August 29th the red planet Mars, near its closest approach to Earth in almost 60,000 years, shone brightly in the sky against a background of stars in the constellation Aquarius. In the foreground of this scary view, huge thunder clouds are lit by lightning strokes from within. Mars, of course, has nothing to do with storms on Earth, though both have the power to excite the imagination and wonder of Earthdwellers. Tonight, the night before Halloween, Mars will also pass close to the Earth, closer than it will come during the next thirteen years. And once again, the red planet Mars will look particularly bright, although much smaller and dimmer than the Moon and even Venus.

Credit : T. Credner & S. Kohle, AlltheSky.com

poon cho tang SG

Astronomy Picture of the Day

2005 October 31

A Martian Halloween

Explanation: From sunset to sunrise, an unusually bright yellowish orb will hang in the sky this Halloween: Mars. Yesterday, Earth passed Mars as they orbited the Sun, bringing Mars closer than it will be for the next thirteen years. Tonight though, Mars will be nearly as bright as last night, a beacon of extraterrestrial spookiness. Opposite the Sun, Mars will rise just when the Sun sets, set just when the Sun rises, and be visible the entire night. Mars will not always be the brightest object in tonight's sky, though. The last quarter Moon will rise near midnight. Brighter than even Mars, almost spooky Venus will light up the western horizon for a brief time just after sunset. Please have a safe and happy All Hallows Eve.

Credit & Copyright: Wally Pacholka (Astropics.com)

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