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

2006 May 20

Elliptical Galaxy M87

Explanation: In spiral galaxies, majestic winding arms of young stars and interstellar gas and dust rotate in a flat disk around a bulging galactic nucleus. But elliptical galaxies seem to be simpler. Lacking gas and dust to form new stars, their randomly swarming older stars, give them an ellipsoidal (egg-like) shape. Still, elliptical galaxies can be very large. Over 120,000 light-years in diameter (larger than our own Milky Way), elliptical galaxy M87 is the dominant galaxy at the center of the Virgo Galaxy Cluster, some 50 million light-years away. M87 is likely home to a supermassive black hole responsible for the high-energy jet of particles emerging from the giant galaxy's central region.

Credit & Copyright: Robert Gendler

poon cho tang SG

Astronomy Picture of the Day

2006 May 21

An Intermediate Polar Binary System

Explanation: How can two stars create such a strange and intricate structure? Most stars are members of multiple-star systems. Some stars are members of close binary systems where material from one star swirls around the other in an accretion disk. Only a handful of stars, however, are members of an intermediate polar, a system featuring a white dwarf star with a magnetic field that significantly pushes out the inner accretion disk, only allowing material to fall down its magnetic poles. Shown above is an artist's depiction of an intermediate polar system, also known as a DQ Hercules system. The foreground white dwarf is so close to the normal star that it strips away its outer atmosphere. As the white dwarf spins, the columns of infalling gas rotate with it. The name intermediate polar derives from observations of emitted light polarized at a level intermediate to non-disk binary systems known as polars. Intermediate polars are a type of cataclysmic variable star system.

Illustration Credit & Copyright: Mark Garlick (Space-art)

poon cho tang SG

Astronomy Picture of the Day

2006 May 22

Maneuvering in Space

Explanation: What arm is 17 meters long and sometimes uses humans for fingers? The Canadarm2 aboard the International Space Station (ISS). Canadarm2 has multiple joints and is capable of maneuvering payloads as massive as 116,000 kilograms, equivalent to a fully loaded bus. Canadarm2 is operated by remote control by a human inside the space station. To help with tasks requiring a particularly high level of precision and detail, an astronaut can be anchored to an attached foot constraint. The arm is able propel itself end-over-end around the outside of the space station. Pictured above, astronaut Stephen Robinson rides Canadarm2 during the STS-114 mission of the space shuttle Discovery to the ISS in 2005 August. Space shuttles often deploy their own original version of a robotic arm dubbed Canadarm. Next year, a second robotic arm is scheduled to be deployed on the space station.

Credit: STS-114 Crew, ISS Expedition 11 Crew, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 May 23

Comet Schwassmann-Wachmann 3 Passes the Earth

Explanation: Rarely does a comet pass this close to Earth. Last week, dedicated astrofilmographers were able to take advantage of the close approach of crumbling 73P / Comet Schwassmann-Wachmann 3 to make time-lapse movies of the fast-moving comet. Large comet fragments passed about 25 times the Moon's distance from the Earth. The above time lapse movie of Fragment B of Comet Schwassmann-Wachmann 3 over Colorado, USA was taken during a single night, May 16, with 83 consecutive 49-second exposures. Some observers report being able to perceive the slight motion of the comet with respect to the background stars using only their binoculars and without resorting to the creation of fancy digital time-lapse movies. Fragment B of Comet Schwassmann-Wachmann 3 became just barely visible to the unaided eye two weeks ago but now is appearing to fade as the comet has moved past the Earth and nears the Sun. Many sky enthusiasts will be on the watch for a particularly active meteor shower tonight as the Earth made its closest approach to orbit of Comet Schwassmann-Wachmann 3 late yesterday.

Credit & Copyright: Thad V'Soske (Cosmotions.com)

poon cho tang SG

Astronomy Picture of the Day

2006 May 24

A Five Quasar Gravitational Lens

Explanation: What's happening near the center of this cluster of galaxies? At first glance, it appears that several strangely elongated galaxies and fully five bright quasars exist there. In reality, an entire cluster of galaxies is acting as a gigantic gravitational lens that distorts and multiply-images bright objects that occur far in the distance. The five bright white points near the cluster center are actually images of a single distant quasar. This Hubble Space Telescope image is so detailed that even the host galaxy surrounding the quasar is visible. Close inspection of the above image will reveal that the arced galaxies at 2 and 4 o'clock are actually gravitationally lensed images of the same galaxy. A third image of that galaxy can be found at about 10 o'clock from the cluster center. Serendipitously, numerous strange and distant galaxies dot the above image like colorful jewels. The cluster of galaxy that acts as the huge gravitational lens is cataloged as SDSS J1004+4112 and lies about 7 billion light years distant toward the constellation of Leo Minor.

Credit: K. Sharon (Tel Aviv U.) and E. Ofek (Caltech), ESA, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 May 25

NGC 1579: Trifid of the North

Explanation: Colorful NGC 1579 resembles the better known Trifid Nebula, but lies much farther north in planet Earth's sky, in the heroic constellation Perseus. About 2,100 light-years away and 3 light-years across, NGC 1579 is a captivating study in color. Like the Trifid, NGC 1579 is a dusty star forming region providing contrasting emission and reflection nebulae in the same field - the characteristic red glow of hydrogen gas and the blue of reflected starlight. Also like the Trifid, dark dust lanes are prominent in the nebula's central regions. In fact, obscuring dust is pervasive in NGC 1579, drastically dimming the visible light from the massive, young, hot stars still embedded in the cosmic cloud.

Credit & Copyright: R. Jay GaBany (Cosmotography.com)

poon cho tang SG

Astronomy Picture of the Day

2006 May 26

Omega Centauri

Explanation: Centaurus, the Centaur, is one of the most striking constellations in the southern sky. The Milky Way flows through this celestial expanse whose wonders also include the closest star to the Sun, Alpha Centauri, and the largest globular star cluster in our galaxy, Omega Centauri. This gorgeous wide-field telescopic view of Omega Centauri shows off the cluster of about 10 million stars and the surrounding star field, with very faint dust clouds and distant background galaxies. Omega Cen itself is about 15,000 light-years away and 150 light-years in diameter - one of 150 or so known globular star clusters that roam the halo of our galaxy. The stars in globular clusters are much older, cooler, and less massive than our Sun.

Credit & Copyright: Steve Crouch

poon cho tang SG

Astronomy Picture of the Day

2006 May 27

Gamma-Ray Moon

Explanation: If you could see gamma rays - photons with a million or more times the energy of visible light - the Moon would appear brighter than the Sun! The startling notion is demonstrated by this image of the Moon from the Energetic Gamma Ray Experiment Telescope (EGRET) in orbit on NASA's Compton Gamma Ray Observatory from April 1991 to June 2000. Then, the most sensitive instrument of its kind, even EGRET could not see the quiet Sun which is extremely faint at gamma-ray energies. So why is the Moon bright? High energy charged particles, known as cosmic rays, constantly bombard the unprotected lunar surface generating gamma-ray photons. EGRET's gamma-ray vision was not sharp enough to resolve a lunar disk or any surface features, but its sensitivity reveals the induced gamma-ray moonglow. So far unique, the image was generated from eight exposures made during 1991-1994 and covers a roughly 40 degree wide field of view with gamma-ray intensity represented in false color.

Credit: Dave Thompson (NASA/GSFC) et al., EGRET, Compton Observatory, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 May 28

GRO J1655-40: Evidence for a Spinning Black Hole

Explanation: In the center of a swirling whirlpool of hot gas is likely a beast that has never been seen directly: a black hole. Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes. The gas surrounding GRO J1655-40, for example, has been found to display an unusual flickering at a rate of 450 times a second. Given a previous mass estimate for the central object of seven times the mass of our Sun, the rate of the fast flickering can be explained by a black hole that is rotating very rapidly. What physical mechanisms actually cause the flickering -- and a slower quasi-periodic oscillation (QPO) -- in accretion disks surrounding black holes and neutron stars remains a topic of much research.

Drawing Credit: A. Hobart, CXC

poon cho tang SG

Astronomy Picture of the Day

2006 May 29

The NASA Television Channel

Explanation: Do you ever feel like watching the NASA channel? If so, in addition to standard cable access and the standard NASA TV web pages, it might now be possible to watch NASA TV simply by accessing today's APOD. Watch cool rocket launches, real-time return of scientific results and images from deep space probes, press conferences, and interviews with scientists, educators, and astronauts. To see the channel optimally, one should have a broadband web connection and Windows Media Player properly installed. Options for watching NASA TV on other platforms are also available. On most computers, a sound adjustment slider is available on the lower right. Double clicking on the image will expand the image to fill your computer screen. A standard schedule is available for NASA's Public TV channel, as well as a live events listing and an educational programming guide.

Credit: NASA TV, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 May 30

Ancient Craters on Saturn's Rhea

Explanation: Saturn's ragged moon Rhea has one of the oldest surfaces known. Estimated as changing little in the past billion years, Rhea shows craters so old they no longer appear round their edges have become compromised by more recent cratering. Like Earth's Moon, Rhea's rotation is locked on Saturn, and the above image shows part of Rhea's surface that always faces Saturn. Rhea's leading surface is more highly cratered than its trailing surface. Rhea is composed mostly of water-ice but is thought to have a small rocky core. The above image was taken by the robot Cassini spacecraft now orbiting Saturn. Cassini swooped past Rhea two months ago and captured the above image from about 100,000 kilometers away. Rhea spans 1,500 kilometers making it Saturn's second largest moon after Titan. Several surface features on Rhea remain unexplained including large light patches.

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

poon cho tang SG

Astronomy Picture of the Day

2006 May 31

Simulated Gamma-ray Sky

Explanation: Scheduled for launch in 2007, the Gamma-ray Large Area Space Telescope (GLAST) will explore the Universe in gamma-rays, the most energetic form of light. To get ready, consider this dynamic gamma-ray sky animation - constructed from simulating the first 55 days (seen above at one frame per day) of GLAST observations of cosmic gamma-ray sources. The all-sky view is projected in an astronomical (RA-Dec) coordinate system that shows the plane of our Milky Way Galaxy as a broad U-shape, with the center of the galaxy toward the right. So what shines in this gamma-ray sky? Besides the diffuse Milky Way glow, astronomers testing their skills on the simulated data have found flaring active galaxies, pulsars, gamma-ray bursts, the flaring Sun, and of course, the gamma-ray Moon.

Credit: GLAST DC2

poon cho tang SG

Astronomy Picture of the Day

2006 June 1

Reflections on NGC 6188

Explanation: NGC 6188 is an interstellar carnival of young blue stars, hot red gas, and cool dark dust. Located 4,000 light years away in the disk of our Galaxy, NGC 6188 is home to the Ara OB1 association, a group of bright young stars whose nucleus forms the open cluster NGC 6193. These stars are so bright that some of their blue light reflects off of interstellar dust forming the diffuse blue glow surrounding them stars in the above photograph. Open cluster NGC 6193 formed about three million years ago from the surrounding gas, and appears unusually rich in close binary stars. The red glow visible throughout the photograph arises from hydrogen gas heated by the bright stars in Ara OB1. The dark dust that blocks much of NGC 6188's light was likely formed in the outer atmospheres of cooler stars and in supernovae ejecta.

Credit & Copyright: Robert Gendler & Martin Pugh

poon cho tang SG

Astronomy Picture of the Day

2006 June 2

IC 443: Supernova Remnant and Neutron Star

Explanation: IC 443 is typical of the aftermath of a stellar explosion, the ultimate fate of massive stars. Seen in this false-color composite image, the supernova remnant is still glowing across the spectrum, from radio (blue) to optical (red) to x-ray (green) energies -- even though light from the stellar explosion that created the expanding cosmic cloud first reached planet Earth thousands of years ago. The odd thing about IC 443 is the apparent motion of its dense neutron star, the collapsed remnant of the stellar core. The close-up inset shows the swept-back wake created as the neutron star hurtles through the hot gas, but that direction is not aligned with the direction toward the apparent center of the remnant. The misalignment suggests that the explosion site was offset from the center or that fast-moving gas in the nebula has influenced the wake. The wide view of IC 443, also known as the Jellyfish nebula, spans about 65 light-years at the supernova remnant's estimated distance of 5,000 light-years.

Credit: Chandra X-ray: NASA/CXC/B.Gaensler et al; ROSAT X-ray: NASA/ROSAT/Asaoka & Aschenbach;
Radio Wide: NRC/DRAO/D.Leahy; Radio Detail: NRAO/VLA; Optical: DSS

poon cho tang SG

Astronomy Picture of the Day

2006 June 3

Gamma-Ray Earth

Explanation: The pixelated planet above is actually our own planet Earth seen in gamma rays - the most energetic form of light. In fact, the gamma rays used to construct this view pack over 35 million electron volts (MeV) compared to a mere two electron volts (eV) for a typical visible light photon. The Earth's gamma-ray glow is indeed very faint, and this image was constructed by combining data from seven years of exposure during the life of the Compton Gamma Ray Observatory, operating in Earth orbit from 1991 to 2000. Brightest near the edge and faint near the center, the picture indicates that the gamma rays are coming from high in Earth's atmosphere. The gamma rays are produced as the atmosphere interacts with high energy cosmic rays from space, blocking the harmful radiation from reaching the surface. Astronomers need to understand Earth's gamma-ray glow well as it can interfere with observations of cosmic gamma-ray sources like pulsars, supernova remnants, and distant active galaxies powered by supermassive black holes.

Credit: Dirk Petry (GLAST Science Support Center), EUD, EGRET, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 June 4

The First Rocket Launch from Cape Canaveral

Explanation: A new chapter in space flight began on 1950 July with the launch of the first rocket from Cape Canaveral, Florida: the Bumper 2. Shown above, the Bumper 2 was an ambitious two-stage rocket program that topped a V-2 missile base with a WAC Corporal rocket. The upper stage was able to reach then-record altitudes of almost 400 kilometers, higher than even modern Space Shuttles fly today. Launched under the direction of the General Electric Company, the Bumper 2 was used primarily for testing rocket systems and for research on the upper atmosphere. Bumper 2 rockets carried small payloads that allowed them to measure attributes including air temperature and cosmic ray impacts. Seven years later, the Soviet Union launched Sputnik I and Sputnik II, the first satellites into Earth orbit. In response, in 1958, the US created NASA.

Credit: GRIN, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 June 5

The Road to Victoria Crater on Mars

Explanation: Here is a road never traveled. To get to Victoria Crater on Mars, the rolling robotic rover Opportunity must traverse the landscape shown above. Victoria Crater lies about one kilometer ahead. The intervening terrain shows a series of light rock outcrops that appears like some sort of cobblestone road. Surrounding this naturally-occurring Martian road, is Martian sand ripples that must be navigated around. Inspection of the outcrop road shows it to be sprinkled with many small round rocks dubbed blueberries. Opportunity and its sister robot Spirit continue their third year exploring Mars. Within the next month, planetary scientists hope to maneuver Opportunity across Meridiani Planum to get a good view of 800-meter diameter Victoria Crater.

Credit: Mars Exploration Rover Mission, Cornell, JPL, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 June 6

NGC 6164: A Bipolar Emission Nebula

Explanation: How did a star form this beautiful nebula? In the middle of emission nebula NGC 6164-5 is an unusually massive star nearing the end of its life. The star, visible in the center of the above image and catalogued as HD 148937, is so hot that the ultraviolet light it emits heats up gas that surrounds it. That gas was likely thrown off from the star, possibly by its fast rotation, like a rotating lawn sprinkler. Expelled material might have been further channeled by the magnetic field of the star, creating the symmetric shape of the bipolar nebula. Several cometary knots of gas are also visible on the lower left. NGC 6164-5 spans about four light years and is located about 4,000 light years away toward the southern constellation Norma.

Credit & Copyright: Gemini Obs., AURA, NSF

poon cho tang SG

Astronomy Picture of the Day

2006 June 7

An Alaskan Volcano Erupts

Explanation: What is happening to that volcano? It's erupting! The first person to note that the Aleutian Cleveland Volcano was spewing ash was astronaut Jeffrey N. Williams aboard the International Space Station. Looking down on the Alaskan Aleutian Islands two weeks ago, Williams noted, photographed, and reported a spectacular ash plume emanating from the Cleveland Volcano. Starting just before this image was taken, the Cleveland Volcano underwent a short eruption lasting only about two hours. The Cleveland stratovolcano is one of the most active in the Aleutian Island chain. The volcano is fueled by magma displaced by the subduction of the northwest-moving tectonic Pacific Plate under the tectonic North America Plate.

Credit: J. N. Williams, International Space Station 13 Crew, NASA

poon cho tang SG

Astronomy Picture of the Day

2006 June 8

Enceladus Ice Volcanos

Explanation: In this stunning Saturnian vista - one in a series of artist's visions of volcanos on alien worlds - icy geysers erupt along narrow fractures in inner moon Enceladus. The majestic plumes were actually discovered by instruments on the Cassini Spacecraft during close encounters with bright and shiny Enceladus last year. Researchers now suspect the plumes originate from near-surface pockets of liquid water with temperatures near 273 kelvins (0 degrees C) - hot when compared to the distant moon's surface temperature of 73 kelvins (-200 degrees C). A dramatic sign that tiny, 500km-diameter Enceladus is surprisingly active, these ice volcanos hold out another potential site in the search for water and origin of life beyond planet Earth. Enceladus' ice volcanos also likely produce Saturn's faint but extended E ring.

Illustration Credit & Copyright: Michael Carroll

« Previous Page Next Page »