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#16    Roj47

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Posted 30 August 2006 - 09:43 AM

It must be as a direct result of sci-fi progs and films that I always imagine space explosions to last seconds and disappear in minutes.

340 years since the explosion and you can still see the outline of the explosion.



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#17    Startraveler

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Posted 30 August 2006 - 06:40 PM

Quote

340 years since the explosion and you can still see the outline of the explosion.


Not just that, Cas A is the brightest thing in the sky (excluding things in our solar system) in radio waves. If not for obscuring dust the supernova would've been a nice sight in the optical here on earth--the only one in our galaxy since the invention of the telescope. Too bad.


#18    Waspie_Dwarf

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Posted 01 September 2006 - 03:49 AM

Long-lasting but Dim Brethren of Cosmic Flashes

The European Southern Observatory (ESO) press release 33-06 is reproduced below:

31 August 2006

Long-lasting but Dim Brethren of Cosmic Flashes

Unusual Gamma-Ray Burst Studied in Detail


Astronomers, using ESO's Very Large Telescope, have for the first time made the link between an X-ray flash and a supernova. Such flashes are the little siblings of gamma-ray bursts (GRB) and this discovery suggests the existence of a population of events less luminous than 'classical' GRBs, but possibly much more numerous.

"This extends the GRB-supernova connection to X-ray flashes and fainter supernovae, implying a common origin," said Elena Pian, (INAF, Italy), lead-author of one of the four papers related to this event appearing in the 31 August issue of Nature.

The event began on 18 February 2006: the NASA/PPARC/ASI Swift satellite detected an unusual gamma-ray burst, about 25 times closer and 100 times longer than the typical gamma-ray burst. GRBs release in a few seconds more energy than that of the Sun during its entire lifetime of more than 10,000 million years. The GRBs are thus the most powerful events since the Big Bang known in the Universe.

user posted image
Region of the sky around the newly discovered X-ray flash/Supernova SN2006aj. The left image comes from the DSS2 survey and is taken in the red filter. The image was taken prior to the explosion and shows at the position of the flash (circle) the tiny host galaxy. The right image shows the VLT FORS image, showing the presence of a bright object, the flash. It is a colour composite, based on images obtained in the B-, V-, and R-filters. The two panels show the the same region at the same scale.

The explosion, called GRB 060218 after the date it was discovered, originated in a star-forming galaxy about 440 million light-years away toward the constellation Aries. This is the second-closest gamma-ray burst ever detected. Moreover, the burst of gamma rays lasted for nearly 2,000 seconds; most bursts last a few milliseconds to tens of seconds. The explosion was surprisingly dim, however.

A team of astronomers has found hints of a budding supernova. Using, among others, ESO's Very Large Telescope (VLT) in Chile, the scientists have watched the afterglow of this burst grow brighter in optical light. This brightening, along with other telltale spectral characteristics in the light, strongly suggests that a supernova was unfolding. Within days, the supernova became apparent.

The observations with the VLT started on 21 February 2006, just three days after the discovery. Spectroscopy was then performed nearly daily for seventeen days, providing the astronomers with a large data set to document this new class of events.

The group led by Elena Pian indeed confirmed that the event was tied to a supernova called SN 2006aj a few days later. Remarkable details about the chemical composition of the star debris continue to be analysed.

The newly discovered supernova is dimmer than hypernovae associated with normal long gamma-ray bursts by about a factor of two, but it is still a factor of 2-3 more luminous than regular core-collapse supernovae.

All together, these facts point to a substantial diversity between supernovae associated with GRBs and supernovae associated with X-ray flashes. This diversity may be related to the masses of the exploding stars.

Whereas gamma-ray bursts probably mark the birth of a black hole, X-ray flashes appear to signal the type of star explosion that leaves behind a neutron star. Based on the VLT data, a team led by Paolo Mazzali of the Max Planck Institute for Astrophysics in Garching, Germany, postulate that the 18 February event might have led to a highly magnetic type of neutron star called a magnetar.

Mazzali and his team find indeed that the star that exploded had an initial mass of 'only' 20 times the mass of the Sun. This is smaller, by about a factor two at least, than those estimated for the typical GRB-supernovae.

"The properties of GRB 060218 suggest the existence of a population of events less luminous than 'classical' GRBs, but possibly much more numerous", said Mazzali. "Indeed, these events may be the most abundant form of X- or gamma-ray bursts in the Universe, but instrumental limits allow us to detect them only locally."

The astronomers find that the number of such events could be about 100 times more numerous than typical gamma-ray bursts.


Source: ESO Press Release pr-33-06

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#19    Waspie_Dwarf

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Posted 19 September 2006 - 12:56 AM

New evidence links stellar remains to oldest recorded supernova

user posted image
Integrated The combined image from the Chandra and XMM-Newton X-ray observatories of RCW 86 shows the expanding ring of debris that was created after a massive star in the Milky Way collapsed onto itself and exploded. Both the XMM-Newton and Chandra images show low energy X-rays in red, medium energies in green and high energies in blue. The Chandra observations focused on the northeast (left-hand) side of RCW 86, and show that X-ray radiation is produced both by high-energy electrons accelerated in a magnetic field (blue) as well as heat from the blast itself (red).
Properties of the shell in the Chandra image, along with the remnant's size and a basic understanding of how supernovas expand, were used to help determine the age of RCW 86. The new data revealed that RCW 86 was created by a star that exploded about 2000 years ago. This age matches observations of a new bright star by Chinese astronomers in 185 AD (and possibly Romans as well) and may be the oldest known recordings of a supernova. Supernova explosions in galaxies like ours are rare, and none have been recorded in hundreds of years.

Credits: ESA/XMM, NASA/CXC, University of Utrecht (J. Vink)


18 September 2006
Recent observations from the European Space Agency's XMM-Newton Observatory and NASA's Chandra X-ray Observatory have uncovered evidence that helps to confirm the identification of the remains of one of the earliest stellar explosions recorded by humans.

The new study shows that the supernova remnant 'RCW 86', observed by XMM-Newton and Chandra, is much younger than previously thought. As such, the formation of the remnant appears to coincide with a supernova observed by Chinese astronomers in 185 AD.
"There have been previous suggestions that RCW 86 is the remains of the supernova from 185 AD," said Jacco Vink of University of Utrecht, The Netherlands, and lead author of the study. "These new X-ray data greatly strengthen the case."  

When a massive star runs out of fuel, it collapses on itself, creating a supernova that can outshine an entire galaxy. The intense explosion hurls the outer layers of the star into space and produces powerful shock waves. The remains of the star and the material it encounters are heated to millions of degrees and can emit intense X-ray radiation for thousands of years.

In their stellar forensic work, Vink and colleagues studied the debris in RCW 86 to estimate when its progenitor star originally exploded. They calculated how quickly the shocked, or energized, shell is moving in RCW 86, by studying one part of the remnant. They combined this expansion velocity with the size of the remnant and a basic understanding of how supernovas expand to estimate the age of RCW 86.

"Our new calculations tell us the remnant is about 2000 years old," said Aya Bamba, a co-author from the Institute of Physical and Chemical Research (RIKEN), Japan. "Previously astronomers had estimated an age of 10 000 years."

user posted image
The XMM-Newton EPIC (MOS/PN) mosaic (left)shows the expanding ring of debris of RCW 86, the oldest ever-recorded supernova remnant. On the right, the same object observed by the Archival Molonglo Observatory Synthesis Telescope (MOST).

Credits: University of Utrecht (J. Vink), ESA/XMM-Newton, MOST
  

The younger age for RCW 86 may explain an astronomical event observed almost 2000 years ago. In 185 AD, Chinese astronomers (and possibly the Romans) recorded the appearance of a new bright star.

The Chinese noted that it sparkled like a star and did not appear to move in the sky, arguing against it being a comet. Also, the observers noticed that the star took about eight months to fade, consistent with modern observations of supernovas.

RCW 86 had previously been suggested as the remnant from the 185 AD event, based on the historical records of the object's position. However, uncertainties about the age provided significant doubt about the association.

"Before this work I had doubts myself about the link, but our study indicates that the age of RCW 86 matches that of the oldest known supernova explosion in recorded history," said Vink. "Astronomers are used to referencing results from 5 or 10 years ago, so it's remarkable that we can build upon work from nearly 2000 years ago."

The smaller age estimate for the remnant follows directly from a higher expansion velocity. By examining the energy distribution of the X-rays, a technique known as spectroscopy, the team found most of the X-ray emission was caused by high-energy electrons moving through a magnetic field. This is a well-known process that normally gives rise to low-energy radio emission. However, only very high shock velocities can accelerate the electrons to such high energies that X-ray radiation is emitted.

"The energies reached in this supernova remnant are extremely high," said Andrei Bykov, another team member from the Ioffe Institute, St. Peterburg, Russia. "In fact, the particle energies are greater than what can be achieved by the most modern particle accelerators."

The difference in age estimates for RCW 86 is due to differences in expansion velocities measured for the supernova remnant. The authors speculate that these variations arise because RCW 86 is expanding into an irregular bubble blown by a wind from the progenitor star before it exploded. In some directions, the shock wave has encountered a dense region outside the bubble and slowed down, whereas in other regions the shock remains inside the bubble and is still moving rapidly. These regions give the most accurate estimate of the age.

Note

The study describing these results appeared in the 1 September 2006 issue of The Astrophysical Journal Letters, in the article titled: "The X-ray synchrotron emission of RCW 86 and the implications for its age", by Jacco Vink et al.

XMM-Newton is an European Space Agency science mission managed at the European Space Research and Technology Centre, Noordwijk, The Netherlands. NASA's Marshall Space Flight Center, Huntsville, Alabama, USA, manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory, Cambridge, Massachussets, USA, controls science and flight operations from the Chandra X-ray Center, Cambridge, Massachussets, USA.


Source: ESA - News

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#20    RollingThunder06

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Posted 20 September 2006 - 02:42 AM

This is so awesome that they have found something linked to about 2000 years ago. Not only does it tell us history is alive it also helps verify what people saw and recorded.

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#21    Waspie_Dwarf

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Posted 25 October 2006 - 12:51 AM

Crab Nebula: The Spirit of Halloween Lives on as a Dead Star Creates Celestial Havoc

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Credit: X-ray: NASA/CXC/ASU/J.Hester et al.; Optical: NASA/ESA/ASU/J.Hester & A.Loll; Infrared: NASA/JPL-Caltech/Univ. Minn./R.Gehrz

According to the folklore of the Celts and other ancient cultures, Halloween marked the midpoint between the autumnal equinox and the winter solstice on the astronomical calendar, a spooky night when spirits of the dead spread havoc upon their return to Earth.

Nowadays, Halloween is primarily a time for children to dress in costume and demand treats, but the original spirit of Halloween lives on in the sky in the guise of the Crab Nebula.

A star's spectacular death in the constellation Taurus was observed on Earth as the supernova of 1054 A.D. Now, almost a thousand years later, a superdense neutron star left behind by the stellar death is spewing out a blizzard of extremely high-energy particles into the expanding debris field known as the Crab Nebula.

This composite image uses data from three of NASA's Great Observatories. The Chandra X-ray image is shown in light blue, the Hubble Space Telescope optical images are in green and dark blue, and the Spitzer Space Telescope's infrared image is in red. The size of the X-ray image is smaller than the others because ultrahigh-energy X-ray emitting electrons radiate away their energy more quickly than the lower-energy electrons emitting optical and infrared light. The neutron star, which has the mass equivalent to the sun crammed into a rapidly spinning ball of neutrons twelve miles across, is the bright white dot in the center of the image.

Source: Chandra - Photo Album

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#22    Waspie_Dwarf

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Posted 26 October 2006 - 09:30 PM

NASA's Spitzer Peels Back Layers of Star's Explosion

Astronomers using NASA's infrared Spitzer Space Telescope have discovered that an exploded star, named Cassiopeia A, blew up in a somewhat orderly fashion, retaining much of its original onion-like layering.

"Spitzer has essentially found key missing pieces of the Cassiopeia A puzzle," said Jessica Ennis of the University of Minnesota, Minneapolis, lead author of a paper to appear in the Nov. 20 issue of the Astrophysical Journal.

linked-image
Image above: This image from NASA's Spitzer Space Telescope shows
the scattered remains of an exploded star named Cassiopeia A.
Image credit: NASA/JPL-Caltech/Univ. of Minn.


"We've found new bits of the 'onion' layers that had not been seen before," said Dr. Lawrence Rudnick, also of the University of Minnesota, and principal investigator of the research. "This tells us that the star's explosion was not chaotic enough to stir its remains into one big pile of mush."

Cassiopeia A, or Cas A for short, is what is known as a supernova remnant. The original star, about 15 to 20 times more massive than our sun, died in a cataclysmic "supernova" explosion relatively recently in our own Milky Way galaxy. Like all mature massive stars, the Cas A star was once neat and tidy, consisting of concentric shells made up of various elements. The star's outer skin consisted of lighter elements, such as hydrogen; its middle layers were lined with heavier elements like neon; and its core was stacked with the heaviest elements, such as iron.

Until now, scientists were not exactly sure what happened to the Cas A star when it ripped apart. One possibility is that the star exploded in a more or less uniform fashion, flinging its layers out in successive order. If this were the case, then those layers should be preserved in the expanding debris. Previous observations revealed portions of some of these layers, but there were mysterious gaps.

Spitzer was able to solve the riddle. It turns out that parts of the Cas A star had not been shot out as fast as others when the star exploded. Imagine an onion blasting apart with some layered chunks cracking off and zooming away, and other chunks from a different part of the onion shooting off at slightly slower speeds.

"Now we can better reconstruct how the star exploded," said Dr. William Reach of NASA's Spitzer Science Center, Pasadena, Calif. "It seems that most of the star's original layers flew outward in successive order, but at different average speeds depending on where they started."

How did Spitzer find the missing puzzle pieces? As the star's layers whiz outward, they are ramming, one by one, into a shock wave from the explosion and heating up. Material that hit the shock wave sooner has had more time to heat up to temperatures that radiate X-ray and visible light. Material that is just now hitting the shock wave is cooler and glowing with infrared light. Consequently, previous X-ray and visible-light observations identified hot, deep-layer material that had been flung out quickly, but not the cooler missing chunks that lagged behind. Spitzer's infrared detectors were able to find the missing chunks - gas and dust consisting of the middle-layer elements neon, oxygen and aluminum.

Cassiopeia A is the ideal target for studying the anatomy of a supernova explosion. Because it is young and relatively close to our solar system, it is undergoing its final death throes right in front of the watchful eyes of various telescopes. In a few hundred years or so, Cas A's scattered remains will have completely mixed together, forever erasing important clues about how the star lived and died.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.

For more information about Spitzer, visit http://www.nasa.gov/...main/index.html
or http://www.spitzer.caltech.edu/spitzer.

Media contact: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

2006-134


Source: NASA - Spitzer - News

Edited by Waspie_Dwarf, 18 December 2006 - 07:05 PM.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#23    Waspie_Dwarf

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Posted 26 October 2006 - 09:43 PM

Lighting Up a Dead Star's Layers

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This image from NASA's Spitzer Space Telescope shows the scattered remains of an exploded star named Cassiopeia A. Spitzer's infrared detectors "picked" through these remains and found that much of the star's original layering had been preserved.

In this false-color image, the faint, blue glow surrounding the dead star is material that was energized by a shock wave, called the forward shock, which was created when the star blew up. The forward shock is now located at the outer edge of the blue glow. Stars are also seen in blue. Green, yellow and red primarily represent material that was ejected in the explosion and heated by a slower shock wave, called the reverse shock wave.

The picture was taken by Spitzer's infrared array camera and is a composite of 3.6-micron light (blue); 4.5-micron light (green); and 8.0-micron light (red).

Image credit: NASA/JPL-Caltech/Univ. of Minn.

+ High resolution image


Source: NASA - Spitzer - Multimedia


"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#24    Waspie_Dwarf

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Posted 26 October 2006 - 09:47 PM

Order Amidst Chaos of Star's Explosion

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This artist's animation shows the explosion of a massive star, the remains of which are named Cassiopeia A. NASA's Spitzer Space Telescope found evidence that the star exploded with some degree of order, preserving chunks of its onion-like layers as it blasted apart.

Cassiopeia A is what is known as a supernova remnant. The original star, about 15 to 20 times more massive than our sun, died in a cataclysmic "supernova" explosion viewable from Earth about 340 years ago. The remnant is located 10,000 light-years away in the constellation Cassiopeia.

The movie begins by showing the star before it died, when its layers of elements (shown in different colors) were stacked neatly, with the heaviest at the core and the lightest at the top. The star is then shown blasting to smithereens. Spitzer found evidence that the star's original layers were preserved, flinging outward in all directions, but not at the same speeds. In other words, some chunks of the star sped outward faster than others, as illustrated by the animation.

The movie ends with an actual picture of Cassiopeia A taken by Spitzer. The colored layers containing different elements are seen next to each other because they traveled at different speeds.

The infrared observatory was able to see the tossed-out layers because they light up upon ramming into a "reverse" shock wave created in the aftermath of the explosion. When a massive star explodes, it creates two types of shock waves. The forward shock wave darts out quickest, and, in the case of Cassiopeia A, is now traveling at supersonic speeds up to 7,500 kilometers per second (4,600 miles/second). The reverse shock wave is produced when the forward shock wave slams into a shell of surrounding material expelled before the star died. It tags along behind the forward shock wave at slightly slower speeds.

Chunks of the star that were thrown out fastest hit the shock wave sooner and have had more time to heat up to scorching temperatures previously detected by X-ray and visible-light telescopes. Chunks of the star that lagged behind hit the shock wave later, so they are cooler and radiate infrared light that was not seen until Spitzer came along. These lagging chunks are seen in false colors in the Spitzer picture of Cassiopeia A. They are made up of gas and dust containing neon, oxygen and aluminum -- elements from the middle layers of the original star.

Image credit: NASA/JPL-Caltech

+ High resolution image


Source: NASA - Spitzer - Multimedia

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#25    Waspie_Dwarf

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Posted 26 October 2006 - 09:51 PM

Once an Onion, Always an Onion (artist concept)

user posted image

This artist's concept illustrates a massive star before and after it blew up in a cataclysmic "supernova" explosion. NASA's Spitzer Space Telescope found evidence that this star the remains of which are named Cassiopeia A -- exploded with some degree of order, preserving chunks of its onion-like layers as it blasted apart.

Cassiopeia A is located 10,000 light-years away in the constellation Cassiopeia. It was once a massive star 15 to 20 times larger than our sun. Its fiery death would have been viewable from Earth about 340 years ago.

The top figure shows the star before it died, when its layers of elements were stacked neatly, with the heaviest at the core and the lightest at the top. Spitzer found evidence that these layers were preserved when the star exploded, flinging outward in all directions, but not at the same speeds. As a result, some chunks of the layered material traveled farther out than others, as illustrated in the bottom drawing.

The infrared observatory was able to see the tossed-out layers, because they light up upon ramming into a "reverse" shock wave created in the aftermath of the explosion. When a massive star explodes, it creates two types of shock waves. The forward shock wave darts out quickest, and, in the case of Cassiopeia A, is now traveling at supersonic speeds up to 7,500 kilometers per second (4,600 miles/second). The reverse shock wave is produced when the forward shock wave slams into a shell of surrounding material expelled before the star died. It tags along behind the forward shock wave at slightly slower speeds.

Chunks of the star that were thrown out fastest hit the shock wave sooner and have had more time to heat up to scorching temperatures previously detected by X-ray and visible-light telescopes. Chunks of the star that lagged behind hit the shock wave later, so they are cooler and radiate infrared light that was not seen until Spitzer came along. These lagging chunks are made up of gas and dust containing neon, oxygen and aluminum -- elements from the middle layers of the original star.

Image credit: NASA/JPL-Caltech

+ High resolution image


Source: NASA - Spitzer - Multimedia

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#26    Waspie_Dwarf

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Posted 15 November 2006 - 05:38 PM

Chandra Discovers Relativistic Pinball Machine

The IPB Image press release is reproduced below:

11.15.06
Steve Roy
Marshall Space Flight Center, Huntsville, Ala.
(Phone: 256-544-0034)

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
(Phone: 617-496-7998)

RELEASE: 06-131

New clues about the origins of cosmic rays, mysterious high-energy particles that bombard the Earth, have been revealed using NASA's Chandra X-ray Observatory. An extraordinarily detailed image of the remains of an exploded star provides crucial insight into the generation of cosmic rays.

IPB Image
Image above: This extraordinarily deep Chandra image shows Casseiopeia A, the youngest supernova remnant in the Milky Way.
Image credit: NASA/CXC/UMass Amherst/M.D.Stage et al.


For the first time, astronomers have mapped the rate of acceleration of cosmic ray electrons in a supernova remnant. The new map shows that the electrons are being accelerated at close to the theoretically maximum rate. This discovery provides compelling evidence that supernova remnants are key sites for energizing charged particles.

The map was created from an image of Cassiopeia A, a 325-year-old remnant produced by the explosive death of a massive star. The blue, wispy arcs in the image trace the expanding outer shock wave where the acceleration takes place. The other colors in the image show debris from the explosion that has been heated to millions of degrees.

"Scientists have theorized since the 1960s that cosmic rays must be created in the tangle of magnetic fields at the shock, but here we can see this happening directly," said Michael Stage of the University of Massachusetts, Amherst. "Explaining where cosmic rays come from helps us to understand other mysterious phenomena in the high-energy universe."

Examples are the acceleration of charged particles to high energies in a wide variety of objects, ranging from shocks in the magnetosphere around Earth to awesome extragalactic jets that are produced by supermassive black holes and are thousands of light years in length.

Scientists had previously developed a theory to explain how charged particles can be accelerated to extremely high energies -- traveling at almost the speed of light -- by bouncing back and forth across a shock wave many times.

"The electrons pick up speed each time they bounce across the shock front, like they're in a relativistic pinball machine," said team member Glenn Allen of the Massachusetts Institute of Technology (MIT), Cambridge. "The magnetic fields are like the bumpers, and the shock is like a flipper."

In their analysis of the huge data set, the team was able to separate the X-rays coming from the accelerating electrons from those coming from the heated stellar debris. The data imply that some of these electrons are accelerated at a rate close to the maximum predicted by theory. Cosmic rays are composed of electrons, protons, and ions, of which only glow from electrons is detectable in X-rays. Protons and ions, which constitute the bulk of cosmic rays, are expected to behave similarly to the electrons.

"It's exciting to see regions where the glow produced by cosmic rays actually outshines the 10-million-degree gas heated by the supernova's shock waves," said John Houck, also of MIT. "This helps us understand not only how cosmic rays are accelerated, but also how supernova remnants evolve."

As the total energy of the cosmic rays behind the shock wave increases, the magnetic field behind the shock is modified, along with the character of the shock wave itself. Researching the conditions in the shocks helps astronomers trace the changes of the supernova remnant with time, and ultimately better understand the original supernova explosion.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center, Cambridge, Mass.

Additional information and images can be found at:



Source: NASA Press Release 06-131

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#27    Waspie_Dwarf

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    Oscar Wilde

Posted 15 November 2006 - 05:50 PM

Cassiopeia A: Chandra Discovers Relativistic Pinball Machine

IPB Image
Credit: NASA/CXC/UMass Amherst/M.D.Stage et al.

This extraordinarily deep Chandra image shows Cassiopeia A (Cas A, for short), the youngest supernova remnant in the Milky Way. New analysis shows that this supernova remnant acts like a relativistic pinball machine by accelerating electrons to enormous energies. The blue, wispy arcs in the image show where the acceleration is taking place in an expanding shock wave generated by the explosion. The red and green regions show material from the destroyed star that has been heated to millions of degrees by the explosion.

IPB Image
Credit: NASA/CXC/UMass Amherst/M.D.Stage et al.
Acceleration Map of Cassiopeia A
This figure shows regions in Cas A where the X-ray emission is generated by electrons spiraling along magnetic field lines and being accelerated as they pass across the remnant's shock front. In this acceleration map, the brighter parts of the image show where the acceleration is occurring relatively quickly. In the brightest areas the electrons are being accelerated almost as fast as theoretically possible.
Scale: Image is 7.3 arcmin across

Astronomers have used this data to make a map, for the first time, of the acceleration of electrons in a supernova remnant. Their analysis shows that the electrons are being accelerated to almost the maximum theoretical limit in some parts of Cas A. Protons and ions, which make up the bulk of cosmic rays, are expected to be accelerated in a similar way to the electrons. Therefore, this discovery provides strong evidence that supernova remnants are key sites for energizing cosmic rays.

IPB Image
Credit: NASA/CXC/UMass Amherst/M.D.Stage et al.
Temperature Map of Cassiopeia A
This image shows the temperature of the gas in the supernova remnant Cas A, assuming that the X-ray emission is caused by heat generated by the stellar explosion. Brighter regions represent higher temperatures. Although most of the remnant's X-ray emission is explained by heat from the explosion, in some regions the X-ray emission appears to be caused by a different mechanism. In the brightest regions of the image, corresponding to the blue regions in the 3-color image, energetic electrons spiral along magnetic field lines and are accelerated, generating X-rays that are detected by Chandra.
Scale: Image is 7.3 arcmin across

Charged particles are believed to scatter or bounce off tangled magnetic fields in the shock wave, which act like bumpers in a pinball machine. When the particles cross the shock front they are accelerated, like they received a kick from a flipper in a pinball machine. Typically it should take a few hundred scatterings off the shock's magnetic field before the particles cross the shock front. It then takes about 200 crossings of the shock front to accelerate the particles seen in the Chandra data. Scientists estimate it would take about 200 years -- over half the age of the remnant -- for the electrons to be accelerated to cosmic ray energies, and about 50 years for the most energetic protons and ions observed to be accelerated.

Source: Chandra - Photo Album

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#28    Waspie_Dwarf

Waspie_Dwarf

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Posted 01 December 2006 - 05:34 PM

Asymmetric Ashes

The European Southern Observatory (ESO) press release 44-06 is reproduced below:

ESO 44/06 - Science Release

30 November 2006
Under Embargo until Thursday, 30 November 2006, 20:00 CEST (7:00 pm GMT or 2:00 pm EST)


Asymmetric Ashes

Astronomers Study Shape of Stellar Candles


Astronomers are reporting remarkable new findings that shed light on a decade-long debate about one kind of supernovae, the explosions that mark a star's final demise: does the star die in a slow burn or with a fast bang? From their observations, the scientists find that the matter ejected by the explosion shows significant peripheral asymmetry but a nearly spherical interior, most likely implying that the explosion finally propagates at supersonic speed.

These results are reported today in Science Express, the online version of the research journal Science, by Lifan Wang, Texas A&M University (USA), and colleagues Dietrich Baade and Ferdinando Patat from ESO.

"Our results strongly suggest a two-stage explosion process in this type of supernova," comments Wang. "This is an important finding with potential implications in cosmology."

IPB Image

Using observations of 17 supernovae made over more than 10 years with ESO's Very Large Telescope and the McDonald Observatory's Otto Struve Telescope, astronomers inferred the shape and structure of the debris cloud thrown out from Type Ia supernovae. Such supernovae are thought to be the result of the explosion of a small and dense star - a white dwarf - inside a binary system. As its companion continuously spills matter onto the white dwarf, the white dwarf reaches a critical mass, leading to a fatal instability and the supernova. But what sparks the initial explosion, and how the blast travels through the star have long been thorny issues.

The supernovae Wang and his colleagues observed occurred in distant galaxies, and because of the vast cosmic distances could not be studied in detail using conventional imaging techniques, including interferometry. Instead, the team determined the shape of the exploding cocoons by recording the polarisation of the light from the dying stars.

Polarimetry relies on the fact that light is composed of electromagnetic waves that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light.

This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition.

"Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth."

"This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument,"
he adds.

The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy, it is.

"This has some impact on the use of Type Ia supernovae as standard candles,"
says Ferdinando Patat. "This kind of supernovae is used to measure the rate of acceleration of the expansion of the Universe, assuming these objects behave in a uniform way. But asymmetries can introduce dispersions in the quantities observed."

"Our discovery puts strong constraints on any successful models of thermonuclear supernova explosions," adds Wang.

Models have suggested that the clumpiness is caused by a slow-burn process, called 'deflagration', and leaves an irregular trail of ashes. The smoothness of the inner regions of the exploding star implies that at a given stage, the deflagration gives way to a more violent process, a 'detonation', which travels at supersonic speeds - so fast that it erases all the asymmetries in the ashes left behind by the slower burning of the first stage, resulting in a smoother, more homogeneous residue.

More Information

The results presented here are reported in "Spectropolarimetric diagnostics of thermonuclear explosions", by Lifan Wang, Dietrich Baade and Ferdinando Patat, Science Express, 30 November 2006. The article is also available as astro-ph/0611902.


Source: ESO Press Release pr-44-06

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#29    Waspie_Dwarf

Waspie_Dwarf

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Posted 01 December 2006 - 09:54 PM

Great Observatories Observe Oddball Supernova Remnant

Written by Jim Keller, Spitzer Science Center
November 29, 2006


NASA's Great Observatories -- Spitzer, Hubble, and Chandra -- are working together to unlock the mysterious structure of a supernova remnant in a nearby galaxy.

Supernova Remnant N49 is, in optical light, the brightest supernova remnant in the Large Magellanic Cloud, a nearby satellite galaxy of our own Milky Way Galaxy. To visible-light observatories, N49 appears to have a unique, lopsided filamentary structure which has long puzzled scientists because most supernova remnants appear spherical in shape.

IPB Image
N49 is the brightest supernova remnant (in
optical light) in the Large Magellanic Cloud.
X-ray: NASA/CXC/Caltech/S.Kulkarni et al.;
Optical: NASA/STScI/UIUC/Y.H.Chu &
R.Williams et al.; IR: NASA/JPL-Caltech/
R.Gehrz et al.


By using Spitzer and Chandra to map gas and dust in the area, astronomers have determined that the funny shape of N49 is being caused by the supernova remnant expanding into a region of denser gas on one side.

Infrared emission (red in the image) comes mostly from gas being heated up by the supernova remnant's expanding shell. Surprisingly, not as much of the infrared light is due to dust particles, as is seen in other supernova remnants. Hubble mapped the visible-light structure, which can be seen as yellow and white in the image, and Chandra mapped the location of hot gas, which can be seen as blue in the image.

NASA's Great Observatories Program is a family of four orbiting observatories, each observing the Universe in a different kind of light (visible, gamma rays, X-rays, and infrared). The Spitzer Space Telescope is the infrared Great Observatory. Other missions in this program include the Hubble Space Telescope, the Chandra X-Ray Observatory, and the now-defunct Compton Gamma-Ray Observatory.


Source: Spitzer / Caltech - Happenings

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#30    Waspie_Dwarf

Waspie_Dwarf

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Posted 01 December 2006 - 10:04 PM

IPB Image
X-ray: NASA/CXC/Caltech/S.Kulkarni et al.; Optical: NASA/STScI/UIUC/Y.H.Chu & R.Williams et al.; IR: NASA/JPL-Caltech/R.Gehrz et al.

Stellar Debris in the Large Magellanic Cloud

This is a composite image of N49, the brightest supernova remnant in optical light in the Large Magellanic Cloud. The Chandra X-ray image (blue) shows million-degree gas in the center. Much cooler gas at the outer parts of the remnant is seen in the infrared image from Spitzer (red). While astronomers expected that dust particles were generating most of the infrared emission, the study of this object indicates that much of the infrared is instead generated in heated gas.

The unique filamentary structure seen in the optical image by Hubble (white & yellow) has long set N49 apart from other well understood supernova remnants, as most supernova remnants appear roughly circular in visible light. Recent mapping of molecular clouds suggests that this supernova remnant is expanding into a denser region to the southeast, which would cause its asymmetrical appearance. This idea is confirmed by the Chandra data. Although X-rays reveal a round shell of emission, the X-rays also show brightening in the southeast, confirming the idea of colliding material in that area.

Source: NASA/Caltech - Spitzer - Images

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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