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[Waspie_Dwarf]

X-ray Evidence Supports Possible New Class of Supernova

The press release is reproduced below:

01.04.07

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: 07-001


Evidence for a significant new class of supernova has been found with NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton. These results strengthen the case for a population of stars that evolve rapidly and are destroyed by thermonuclear explosions. Such "prompt" supernovas could be valuable tools for probing the early history of the cosmos.

A team of astronomers uncovered a puzzling situation when they examined X-ray data from DEM L238 and DEM L249, the remnants of two supernovas in a nearby galaxy. On the one hand, the unusually high concentration of iron atoms implied that the remnants are the products of thermonuclear explosions of white dwarf stars, a well-known type of supernova known as Type Ia. On the other hand, the hot gas in the remnants was much denser and brighter in X-rays than typical Type Ia remnants.

A white dwarf, the dense final stage in the evolution of a sun-like star, is a very stable object and will not explode on its own. However, if a white dwarf has a close companion star it can grow beyond a critical mass by pulling gas off the companion and explode.

Computer simulations of Type Ia supernova remnants showed that the most likely explanation for the X-ray data is that the white dwarfs exploded into very dense environments. This suggests that the stars which evolved into these white dwarfs were more massive than usual, because heavier stars are known to expel more gas into their surroundings.

"We know that the more massive a star is, the shorter its lifetime," said Kazimierz Borkowski of North Carolina State University, Raleigh. "If such a star could also begin to pull matter from its companion at an early stage, then this star would have a much shorter fuse and explode in only about 100 million years -- much less than other Type Ia supernovas."

Other teams have independently found evidence for prompt Type Ia explosions using optical observations, but at much greater distances where the environment of the stellar explosion cannot be probed. The X-ray data of DEM L238 and DEM L249 represent nearby examples of prompt Type Ia supernovas.

"We still need to know more about the details of these explosions since they are such an important tool for studying cosmology," said Stephen Reynolds also of North Carolina State University. "So, it's exciting to discover we have some really nearby examples, astronomically speaking, of this different class of explosion."

The luminosity of Type Ia explosions is thought to be very consistent from star to star, and astronomers have used observations of Type Ia supernovas in optical light as cosmic mile markers to study the accelerating expansion of the cosmos caused by dark energy.

If Type Ia supernovas can occur so quickly, they can exist much earlier in the Universe's history than generally believed, allowing them to probe the expansion at these epochs. Another possibility is that the prompt Type Ia’s may also differ in other properties. If so, the assumption that Type Ia’s are standard candles may be compromised, complicating attempts to study dark energy.

"We weren't around to see these stars before they exploded," said Sean Hendrick of Millersville University, Penn., "but these X-ray clues tell us that something unusual happened in the case of these two."

After finding this evidence for prompt Type Ia explosions in the Large Magellanic Cloud, a nearby galaxy, the researchers are looking at other supernova remnants within the Milky Way to see if they might be examples of this potential new class. For example, the famous supernova observed by Johannes Kepler in 1604 might have been a prompt Type Ia supernova.

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

Additional information and images are available at:

http://chandra.harvard.edu/
and
http://www.nasa.gov/chandra/

Source: NASA Press Release 07-001

[Waspie_Dwarf]

DEM L238 and DEM L249: X-ray Evidence Supports Possible New Class Of Supernova


Credit: X-ray: NASA/CXC/NCSU/K.Borkowski; Optical: NOAO/CTIO/MCELS

DEM L238 and DEM L249 are two supernova remnants in the Large Magellanic Cloud. X-ray data from NASA's Chandra and ESA's XMM-Newton observatories suggest that the stars responsible for these debris fields were unusually young when they were destroyed by thermonuclear explosions.

X-ray & Optical


Optical

Chandra X-ray and MCELS Optical Image of DEM L238 and DEM L249
DEM L238 and DEM L249 are two supernova remnants in the Large Magellanic Cloud. X-ray data from NASA's Chandra and ESA's XMM-Newton observatories suggest that the stars responsible for these debris fields were unusually young when they were destroyed by thermonuclear explosions. The large field-of-view is a composite image of DEM L238 (right) and DEM L249, Chandra X-ray data in blue and optical data in white.
(Credit: X-ray: NASA/CXC/NCSU/K.Borkowski; Optical: NOAO/CTIO/MCELS)

The large field-of-view is a composite image of DEM L238 (right) and DEM L249, Chandra X-ray data in blue and optical data in white. The inset reveals how DEM L238 appears in the three bands of X-ray emission (low energy X-rays are shown in red, medium energies in green and high energies in blue.) The central region of DEM L238 is green which indicates that it is rich in iron. This overabundance of iron identifies this object as a so-called Type Ia supernova, one possible explosive death of a star.

Comparison of Type Ia Supernovas
This 4-panel compares the Chandra image of DEM L238 with the Chandra image of 3 Type Ia supernova remnants located in the Milky Way. The X-ray emission for Kepler's remnant contains a bright central region similar to DEM L238, while the X-ray emission for Tycho's remnant and SN 1006 are generally much more uniform. These results suggest that the stars that exploded and caused the DEM L238 and Kepler supernova remnants were much younger than the stars that produced the Tycho and SN 1006 remnants.
(Credit: NASA/CXC)

In a Type Ia supernova, a white dwarf, the dense final stage in the evolution of a sun-like star, pulls so much mass from an orbiting companion star that it cannot support its own weight. The star collapses and temperatures become high enough for carbon fusion to occur. Fusion begins throughout the white dwarf almost simultaneously and an explosion occurs.

A surprising feature of these images is that the iron in the central regions of DEM L238 and DEM L249 is much denser that in most Type Ia supernovas. The most likely explanation for these results is that the white dwarfs exploded into very dense environments. This implies that the stars which evolved into the white dwarfs were more massive than usual, since such stars expel more gas into their surroundings. These stars would explode in much less time -- about 100 million years -- than the billions of years that astronomers think Type Ias typically require.

Source: Chandra - Photo Album

[Bella-Angelique]

Perhaps it is all part of the cycle to produce life in the universe which we are still oblivious of, as essential as rainstorms and summer heat here on earth for the life cycles.

[Waspie_Dwarf]

Quote

Perhaps it is all part of the cycle to produce life in the universe which we are still oblivious of, as essential as rainstorms and summer heat here on earth for the life cycles.

Certainly without supernovae there would be no life. the heavier elements, including the carbon on which we are based are generated in supernova explosions. As to whether that is part of a cycle to produce life or not that is more of a philosophical rather than scientific debate.

What the supernova giveth, the supernova taketh away. Whilst we need the heavy elements produced in a supernova explosion for life a nearby supernova would be catastrophic. The intense blast of radiation would sterilise a planet, killing every living thing.

[Waspie_Dwarf]

A Star's Death Comes to Light

The press release is reproduced below:

01.09.07

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: 07-004


Using NASA's Chandra X-ray Observatory, scientists have created a stunning new image of one of the youngest supernova remnants in the galaxy. This new view of the debris of an exploded star helps astronomers solve a long-standing mystery, with implications for understanding how a star's life can end catastrophically and for gauging the expansion of the universe.

Over 400 years ago, sky watchers -- including the famous astronomer Johannes Kepler -- noticed a bright new object in the night sky. Since the telescope had not yet been invented, only the unaided eye could be used to watch as a new star that was initially brighter than Jupiter dimmed over the following weeks.

Chandra's latest image marks a new phase in understanding the object now known as Kepler's supernova remnant. By combining nearly nine days of Chandra observations, astronomers have generated an X-ray image with unprecedented detail of one of the brightest recorded supernovas in the Milky Way galaxy.

The explosion of the star that created the Kepler remnant blasted the stellar remains into space, heating the gases to millions of degrees and generating highly energized particles. Copious X-ray light, like that shining from many supernova remnants, was produced.

Astronomers have studied Kepler intensively over the past three decades with radio, optical and X-ray telescopes, but its origin has remained a puzzle. On the one hand, the presence of large amounts of iron and the absence of a detectable neutron star points toward a so-called Type Ia supernova. These events occur when a white dwarf star pulls material from an orbiting companion until the white dwarf becomes unstable and is destroyed by a thermonuclear explosion

On the other hand, when viewed in optical light, the supernova remnant appears to be expanding into dense material that is rich in nitrogen. This would suggest Kepler belongs to a different type of supernova (known as "Type II") that is created from the collapse of a single massive star that sheds material before exploding. Type Ia supernovas do not normally have such surroundings.

A team of astronomers, led by Stephen Reynolds of North Carolina State University in Raleigh, N.C., was able to use the Chandra dataset to address this mystery. By comparing the relative amounts of oxygen and iron atoms in the supernova, the scientists were able to determine that Kepler resulted from a Type Ia supernova.

In solving the mystery of Kepler's identity, Reynolds and his team have also given an explanation for the dense material in the remnant. Kepler could be the nearest example of a relatively rare "prompt" Type Ia explosion, which occur in more massive progenitors only about 100 million years after the star formed rather than several billion years.

If that is the case, Kepler could teach astronomers more about all Type Ia supernovas and the ways in which prompt explosions from massive stars differ from their more common cousins associated with lower mass stars.

This information is essential to improve the reliability of the use of Type Ia stars as "standard candles" for cosmological studies of dark energy as well as to understand their role as the source of most of the iron in the universe.

In the new Chandra Kepler image, red represents low-energy X-rays and shows material around the star -- dominated by oxygen -- that has been heated up by a blast wave from the star's explosion. The yellow color shows slightly higher energy X-rays, mostly iron formed in the supernova, while green (medium-energy X-rays) shows other elements from the exploded star. The blue color represents the highest energy X-rays and shows a shock front generated by the 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 are available at:

http://chandra.harvard.edu/
and
http://www.nasa.gov/chandra/

Source: NASA Press Release 07-004

[Waspie_Dwarf]

A Star's Death Comes to Light

Using NASA's Chandra X-ray Observatory, scientists have created a stunning new image of one of the youngest supernova remnants in the galaxy. This new view of the debris of an exploded star helps astronomers solve a long-standing mystery, with implications for understanding how a star's life can end catastrophically and for gauging the expansion of the universe.

Over 400 years ago, sky watchers -- including the famous astronomer Johannes Kepler -- noticed a bright new object in the night sky. Since the telescope had not yet been invented, only the unaided eye could be used to watch as a new star that was initially brighter than Jupiter dimmed over the following weeks. Chandra's latest image marks a new phase in understanding the object now known as Kepler's supernova remnant.
+ Read more/access larger images

Image credit: NASA/CXC/NCSU/S.Reynolds et al.

Source: NASA - Chandra - Multimedia

[Waspie_Dwarf]

Famous Space Pillars Feel the Heat of Star's Explosion

The three iconic space pillars photographed by NASA's Hubble Space Telescope in 1995 might have met their demise, according to new evidence from NASA's Spitzer Space Telescope.


Image above: Infrared view of the Eagle nebula.
Image credit: NASA/JPL-Caltech/ Institut d'Astrophysique Spatiale
+ Full image and caption

A new, striking image from Spitzer shows the intact dust towers next to a giant cloud of hot dust thought to have been scorched by the blast of a star that exploded, or went supernova. Astronomers speculate that the supernova's shock wave could have already reached the dusty towers, causing them to topple about 6,000 years ago. However, because light from this region takes 7,000 years to reach Earth, we won't be able to capture photos of the destruction for another 1,000 years or so.

Spitzer's view of the region is online at http://www.nasa.gov/spitzer and http://www.spitzer.caltech.edu. It shows the entire Eagle nebula, a vast and stormy community of stars set amid clouds and steep pillars made of gas and dust, including the three well-known "Pillars of Creation."

"I remember seeing a photograph of these pillars more than a decade ago and being inspired to become an astronomer," said Nicolas Flagey of The Institut d'Astrophysique Spatiale in France. "Now, we have discovered something new about this region we thought we understood so well." Flagey, a visiting graduate student at NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, presented the results today at the American Astronomical Society meeting in Seattle.

Astronomers have long predicted that a supernova blast wave would mean the end for the popular pillars. The region is littered with 20 or so stars ripe for exploding, so it was only a matter of time, they reasoned, before one would blow up. The new Spitzer observations suggest one of these stellar time bombs has in fact already detonated, an event humans most likely witnessed 1,000 to 2,000 years ago as an unusually bright star in the sky.


Image above: Infrared view of the Eagle
nebula, with an inset of Hubble's view of the
same area.
Image credit: NASA/JPL-Caltech/STScI/
Institut d'Astrophysique Spatiale
+ Full image and caption

Whenever the mighty pillars do crumble, gas and dust will be blown away, exposing newborn stars that were forming inside. A new generation of stars might also spring up from the dusty wreckage.

Spitzer is a space telescope that detects infrared, longer-wavelength light that our eyes cannot see. This allows the observatory to both see the dust and see through it, depending on which infrared wavelength is being observed. In Spitzer's new look at the Eagle nebula, the three pillars appear small and ghostly transparent. They are colored green in this particular view. In the largest of the three columns, an embedded star is seen forming inside the tip.

Above the pillars is the enormous cloud of hot dust, colored red in the picture, which astronomers think was seared by the blast wave of a supernova explosion. Flagey and his team say evidence for this scenario comes from similarities observed between this hot dust and dust around known supernova remnants. The dust also appears to have a shell-like shape, implying that a supernova blast wave is traveling outward and sculpting it.

The mysterious dust was first revealed in previous images from the European Space Agency's Infrared Space Observatory, but Spitzer's longer-wavelength infrared instrument was able to tentatively match the dust to a supernova event.

"Something else besides starlight is heating this dust," said Dr. Alberto Noriega-Crespo, Flagey's advisor at the Spitzer Science Center. "With Spitzer, we now have the missing long-wavelength infrared data that are giving us an answer."

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 Caltech. Caltech manages JPL for NASA.

Spitzer's infrared array camera and multiband imaging photometer made the new observations. The infrared array camera was built by NASA's Goddard Space Flight Center, Greenbelt, Md. The instrument's principal investigator is Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics. The multiband imaging photometer for Spitzer was built by Ball Aerospace Corporation, Boulder, Colo.; the University of Arizona; and Boeing North American, Canoga Park, Calif. Its principal investigator is Dr. George Rieke of the University of Arizona, Tucson.

For additional graphics and more information about Spitzer, visit: http://www.nasa.gov/spitzer or hhttp://www.spitzer.caltech.edu.

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

2007-003

Source: NASA - Spitzer - News

[Waspie_Dwarf]

Superbubble of supernova remnants caught in act of forming

The  University of Illinois at Urbana-Champaign press release is reproduced below:

James E. Kloeppel, Physical Sciences Editor

Released 1/9/07

CHAMPAIGN, Ill. — A superbubble in space, caught in the act of forming, can help scientists better understand the life and death of massive stars, say researchers at the University of Illinois at Urbana-Champaign.

Found within the Small Magellanic Cloud – a galactic neighbor of the Milky Way – the large region of ionized hydrogen gas is designated “LHa115-N19,” and “contains a number of massive stars and overlapping supernova remnants,” said Rosa Williams, an astronomer at the U. of I.
“We can tell there has been a fair amount of stellar activity going on.”

Photo courtesy Rosa Williams

These images show the "LHA 115-N 19" region in the Small Magellanic Cloud. This area hosts a number of massive stars, as well as three supernova remnants (marked in the left-hand image). The amount of activity from massive stars in this region may eventually form a huge low-density cavity called a superbubble.

Left: 3-color image showing emission in an optical hydrogen line taken at Cerro-Tololo Inter-American Observatory (red); radio data from the Australia Telescope Compact Array (green); and X-ray emission from the Chandra X-ray Observatory (blue). Right: 3-color image showing X-ray emission at different energies: low (0.3-0.8 keV) in red, medium (0.8-1.5 keV) in green, and high (1.5-8.0 keV) in blue. The X-ray images have been adaptively smoothed.

From birth to death, massive stars have a tremendous impact on their surroundings. While alive, these stars generate stellar winds that push away nearby gas and dust, forming low-density cavities inside expanding bubbles. When the stars die, shock waves from their death throes can enlarge those bubbles into huge supernova remnants.

“In N19, we have not one star, but a number of massive stars blowing bubbles and we have several supernova remnants,” Williams said. “Some of these cavities may overlap with one another. Eventually, these bubbles could merge into one enormous cavity, called a superbubble.”

To identify the locations of massive stars, stellar-wind bubbles and supernova remnants in N19, Williams and colleagues combined optical images, X-ray data and spectroscopic measurements.

“We caught this particular region of N19 at a neat moment in time,” Williams said. “The stars are just dispersed enough that their stellar winds and supernova blasts are working together, but have not yet carved out a full cavity. We are witnessing the birth of a superbubble.”

The behavior of matter and energy within a superbubble has implications for the formation of planetary systems, said Williams, who will present her team’s findings at the American Astronomical Society meeting in Seattle, on Tuesday (Jan. 9).

During its life and death, a massive star forges the heavy elements that enrich the interstellar medium and form planets. “Our own solar system may have formed within the confines of a superbubble,” said Williams, who uses an analogy with people to help explain her interest in superbubbles.

“Some people live pretty independently in isolated country houses, while others live in large cities that require a centralized structure,” Williams said. “In N19, we are looking at a possible bridge between an individual star living its life and dying its death, and a community of stars, where living and dying affects other stars and planets, and creates a structure around them.”

Collaborators on the project with Williams are You-Hua Chu, Rosie Chen and Robert Gruendl at Illinois, and Sean Points and Chris Smith at the Cerro-Tololo Inter-American Observatory in Chile.

The work was funded by NASA and the Smithsonian Astrophysical Observatory.

Source: UIUC Press Release

[Waspie_Dwarf]

Rethinking last century's closest, brightest supernova

The UC Berkley press release is reproduced below:

By Robert Sanders, Media Relations | 09 January 2007

BERKELEY – Twenty years ago next month, the closest and brightest supernova in four centuries lit up the southern sky, wowing astronomers and the public alike.
Luminous Blue Variable star surrounded by a bipolar nebula


A Luminous Blue Variable star named HD168625, located
in our Milky Way Galaxy, is surrounded by a bipolar nebula
that is similar to the one around SN1987A, a supernova that
exploded in 1987 in the Large Magellanic Cloud and was the
nearest supernova to Earth in 400 years.
(Image credits: NASA, JPL-Caltech, Nathan Smith/UC Berkeley)

Ongoing observations of the exploded star, called supernova 1987A, provided important tests for theories of how stars die, but it also raised some new questions. Principal among these was how a bizarre, triple-ring nebula surrounding the supernova - ejected by the star a few thousand years before it exploded - originated. Astronomers devised a complicated theory that, within a relatively short period of time, the original star, a red supergiant, merged with a companion and started spinning rapidly, then underwent a transition to a blue supergiant, and finally exploded.

University of California, Berkeley, astronomer Nathan Smith has proposed a different theory for the origin of the nebula, arguing instead that SN1987A's progenitor star may have been in a class of unstable blue supergiant stars, called luminous blue variables, which eject material from their surfaces in recurring, volcano-like eruptions before they finally die in a supernova explosion.

Smith recently discovered two such blue supergiant stars with nebulae closely resembling the peculiarly shaped cloud of dust and gas around SN1987A. A third such nebula was already known.

"Taken together, the three closest analogs of SN1987A in our galaxy are all around blue supergiants; two of them have not gone through a red supergiant phase at all, and one was ejected as a luminous blue variable," said Smith, a UC Berkeley postdoctoral researcher. "This makes a pretty solid case that we should rethink models for how the rings around SN1987A were formed.

"If these other stars with rings are likely to explode, it may hint that LBVs and blue supergiants can explode even before becoming red supergiants, which would be a bit of a shock to our understanding of stellar evolution."

Smith will present his findings today (Tuesday, Jan. 9) at a 10:30 a.m. press conference and an all-day poster session during the American Astronomical Society (AAS) meeting in Seattle.

The proximity of SN1987A, only 168,000 light years away in the Large Magellanic Cloud, and the availability of pre-existing data provided the first chance for astronomers to posthumously identify the star that exploded. Astronomers were surprised to find that it had been a hot blue supergiant - not a cooler red supergiant, as most theories predicted at the time.

Adding to the mystery, images taken in the early 1990s by instruments like NASA's Hubble Space Telescope revealed a bizarre, triple-ring nebula. The origin of this nebula and its shaping mechanism are still difficult to understand. The merger theory with conversion from red supergiant to blue supergiant before exploding has become the prevailing view because it accounts for both the blue supergiant and the shape of the nebula.


Diagram explaining the bipolar nebula around the Luminous Blue Variable
HD168625, which has a geometry that makes it a near twin of the famous
nebula around SN1987A. Rings near the equator are sometimes seen around
stars that shed mass from their surfaces, but the larger rings above the poles
are very rare. Tipped toward Earth and illuminated by the star, the rings
look like ellipses in images taken with NASA's Spitzer Space Telescope.

The surprise, Smith said, is that analysis of these new objects in our galaxy that resemble SN1987A provide good reasons to suspect that they ejected and shaped their nebulae while they were still blue supergiants, and not in the transition from red to blue as has been proposed for SN1987A. Furthermore, none of the three stars is spinning rapidly, as one might expect if it had recently merged with a close orbiting companion star. A merger and the subsequent red-to-blue transition are the key ingredients in the prevailing explanation for the nebula around SN1987A, but the three stars discussed by Smith apparently formed similar nebulae without either mechanism.

"We are seeing these nebulae before the stars blow up, and they look quite similar to the nebula around SN1987A," said Smith. "The trouble is, they may contradict how we think the nebula around SN1987A was formed."

According to Smith, the unusual nebula around SN1987A, looking like a figure 8, was originally interpreted to mean that the star had recently been a red supergiant that had shed its outer envelope in an expanding shell, but then turned into a blue supergiant before exploding. The blue supergiant generated a faster wind that overtook the earlier wind and became distorted.

"In that picture, the equatorial ring formed because the slow wind of the red supergiant had more material in the equator, so the waist of the blue supergiant wind was pinched," Smith said. "The fly in the ointment is that in order to get the enhanced density in the equator of the red supergiant, you need it to be spinning rapidly - but red supergiant stars don't do that because they are so big. So the only solution would be if the progenitor of SN1987A swallowed a companion star and the two merged, while the added angular momentum made the red supergiant spin to make a disk."

"This requires that the nearest and best observed supernova in modern history just happens to also be a freak, resulting from a coincidental merger event," he added.

While looking through images taken by NASA's Infrared Array Camera on the Spitzer Space Telescope, however, Smith noticed a similarly weird nebula around a nearby star designated HD168625. This star is a luminous blue variable (or LBV), an unstable massive star that burps from time to time and ejects a bipolar nebula as a blue supergiant, not a red supergiant. A well-known LBV is Eta Carinae, the brightest and most massive star in our Milky Way galaxy, weighing in at more than 100 solar masses.

"This new twin of the SN1987A nebula around an LBV gives us an alternative to the binary merger hypothesis for how these form," Smith said. "It hints that SN1987A may have ejected the nebula as a blue supergiant or an LBV, and not as a red supergiant."

Later, Smith identified a second ring nebula, identical in size to the equatorial ring around SN1987A but surrounding another blue supergiant in our galaxy. He found this in the Carina Nebula in the southern Milky Way in data taken by the 4-meter Blanco telescope at Chile's Cerro Tololo Inter-American Observatory, part of the National Optical Astronomy Observatory, and in images taken by one of two 6.5-meter Magellan telescopes in Chile.

The second star, called SBW1, has almost the same spectral type as the progenitor of SN1987A, but the chemical abundances in the nebula imply that it has not yet been a red supergiant. This directly contradicts the old picture for how the rings around SN1987A were formed, he said. A third similar object in our galaxy, called Sher 25, was already known, and it has chemical abundances that also suggest it has not yet been a red supergiant.

Smith's research was supported by NASA.

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

Source: UC Berkley Press Release

[Waspie_Dwarf]

G11.2-0.3: A Textbook Supernova


Credit: NASA/CXC/Eureka Scientific/M.Roberts et al.

G11.2-0.3 is a circularly symmetric supernova remnant that contains a dense, rotating dead star at its center, representing a textbook case of what the remnant of an exploding star should look like after a couple thousand years. When a massive star collapses, the outer layers of the star are blown away in an extremely energetic explosion. Depending on the mass of the original star, a dense object such as a neutron star or a black hole, can form and be left behind at the explosion's center. Such a neutron star, known as a "pulsar" when it rapidly rotates, can be kicked by the thermonuclear shock wave created when the star exploded, causing it to race through space at millions of miles per hour.

Chandra X-ray & VLA Radio Images of G11.2-0.3
By combining X-ray and radio observations, astronomers have evidence that G11.2-0.3 is likely the result of the explosive death of such a massive star, perhaps witnessed in 386 A.D. Radio observations measure the remnant's expansion rate, which, in turn, can be used to calculate how long ago the star exploded. The radio data is consistent with association of the supernova remnant with the "guest star" reported by Chinese astronomers nearly 2,000 years ago. Chandra's ability to pinpoint the pulsar at nearly the very center of G11.2-0.3 also supports the idea that this debris field could have been created around the time of the Chinese observations.
(Credit: NASA/CXC/Eureka Scientific/M.Roberts et al.)

By combining X-ray and radio observations, astronomers have evidence that G11.2-0.3 is likely the result of the explosive death of such a massive star, perhaps witnessed in 386 A.D. Radio observations measure the remnant's expansion rate, which, in turn, can be used to calculate how long ago the star exploded. The radio data is consistent with association of the supernova remnant with the "guest star" reported by Chinese astronomers nearly 2,000 years ago. Chandra's ability to pinpoint the pulsar at nearly the very center of G11.2-0.3 also supports the idea that this debris field could have been created around the time of the Chinese observations. Surprisingly, the age of the pulsar determined from the X-ray and radio data differs from the standard pulsar age estimate, usually determined from how fast it is spinning. In this case, the so-called spin parameters suggest the G11.2-0.3 is 10 times older than the remnant age. This argues strongly that young pulsar spin ages can be very misleading and should be considered with caution.

In Chandra's X-ray image, the pulsar and a cigar-shaped cloud of energetic particles, known as a pulsar wind nebula, are predominantly seen as high-energy X-rays (blue). A shell of heated gas from the outer layers of the exploded star surrounds the pulsar and the pulsar wind nebula and emits lower-energy X-rays (represented in green and red).

Source: Chandra - Photo Album

[Waspie_Dwarf]

NASA's Hubble Telescope Celebrates SN 1987A's 20th Anniversary

February 22, 2007 10:00 PM (EST)

News Release Number: STScI-2007-10

Twenty years ago, astronomers witnessed one of the brightest stellar explosions in more than 400 years. The titanic supernova, called SN 1987A, blazed with the power of 100 million suns for several months following its discovery on Feb. 23, 1987.

Observations of SN 1987A, made over the past 20 years by NASA's Hubble Space Telescope and many other major ground- and space-based telescopes, have significantly changed astronomers' views of how massive stars end their lives. Astronomers credit Hubble's sharp vision with yielding important clues about the massive star's demise.

"The sharp pictures from the Hubble telescope help us ask and answer new questions about Supernova 1987A," said Robert Kirshner, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "In fact, without Hubble we wouldn't even know what to ask."

Kirshner is the lead investigator of an international collaboration to study the doomed star. Studying supernovae like SN 1987A is important because the exploding stars create elements, such as carbon and iron, that make up new stars, galaxies, and even humans. The iron in a person's blood, for example, was manufactured in supernova explosions. SN 1987A ejected 20,000 Earth masses of radioactive iron. The core of the shredded star is now glowing because of radioactive titanium that was cooked up in the explosion.

The star is 163,000 light-years away in the Large Magellanic Cloud. It actually blew up about 161,000 B.C., but its light arrived here in 1987.

Kirshner has used the Hubble telescope to monitor the supernova. "The Hubble observations have helped us rewrite the textbooks on exploding stars. We found that the actual world is more complicated and interesting than anyone dared to imagine. There are mysterious triple rings of glowing gas and powerful blasts sent out from the explosion that are just having an impact now, 20 years later."

Before SN 1987A, astronomers had a "simplified, idealized model of a supernova," Kirshner explained. "We thought the explosions were spherical and we didn't think much about the gas a star would exhale in the thousands of years before it exploded. The actual shreds of the star in SN 1987A are elongated — more like a jellybean than a gumball, and the fastest-moving debris is slamming into the gas that was already out there from previous millennia. Who would have guessed?"

Hubble wasn't even around when astronomers first spotted the supernova in 1987. When Hubble was launched three years later, astronomers didn't waste any time in using the telescope to study the stellar blast. Its first peek was in 1990, the year the observatory launched. Since then, the telescope has taken hundreds of pictures of the doomed star.

The Hubble studies have revealed the following details about the supernova:

*A glowing ring, about a light-year in diameter, around the supernova. The ring was there at least 20,000 years before the star exploded. X-rays from the explosion energized the gas in the ring, making it glow for two decades.

*Two outer loops of glowing gas that had not been identified in ground-based telescope images.

*A dumbbell-shaped central structure that has now grown to one-tenth of a light-year long. The structure consists of two blobs of debris in the center of the supernova racing away from each other at roughly 20 million miles an hour.

*The onrushing stellar shock wave from the stellar explosion is slamming into, heating up, and illuminating the inner regions of the narrow ring surrounding the doomed star.

Hubble continues to watch as the blast debris moves through the ring. The light show makes the glowing ring look like a pearl necklace. Astronomers think the whole ring will be illuminated in a few years.

The glowing ring is expected to become bright enough to illuminate the star's surroundings, which will provide astronomers with new information on how the star ejected material before the explosion.

Astronomers are analyzing images by NASA's Spitzer Space Telescope to try to understand the fate of the dust that surrounds the exploded star and in the neighborhood around the blast.

"We will learn more in the future when the shock wave moves through the inner ring and slams into the outer rings and illuminates them," Kirshner said. "It could lead to clues about the last 20,000 years of the star. But there are many things that are still a mystery. We still do not understand the evolution of the star before the explosion or how the three rings formed. We also think that the star may be part of a binary system."

Astronomers also are still looking for evidence of a black hole or a neutron star left behind by the blast. The fiery death of massive stars usually creates these energetic objects. Most astronomers think a neutron star formed 20 years ago. Kirshner said the object could be obscured by dust or it could have become a black hole.

He plans to use the infrared capabilities of the Wide Field Camera 3 — an instrument scheduled to be installed during the upcoming Hubble servicing mission — to hunt for a stellar remnant. Scientists will use another instrument planned for installment during the mission, the Cosmic Origins Spectrograph, to analyze the supernova's chemical composition and velocities.

The James Webb Space Telescope, scheduled for launch in 2013, will be able to see infrared light from the ring that is 10 times brighter than what astronomers see today. The debris inside the ring will begin to brighten, and astronomers will get another chance to study the interior of an exploded star.

Source: HubbleSite - Newsdesk

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A String of 'Cosmic Pearls' Surrounds an Exploding Start

News Release Number: STScI-2007-10

ABOUT THIS IMAGE:

Two decades ago, astronomers spotted one of the brightest exploding stars in more than 400 years.

Since that first sighting, the doomed star, called Supernova 1987A, has continued to fascinate astronomers with its spectacular light show. NASA's Hubble Space Telescope is one of many observatories that has been monitoring the blast's aftermath.

This image shows the entire region around the supernova. The most prominent feature in the image is a ring with dozens of bright spots. A shock wave of material unleashed by the stellar blast is slamming into regions along the ring's inner regions, heating them up, and causing them to glow. The ring, about a light-year across, was probably shed by the star about 20,000 years before it exploded.

Astronomers detected the first bright spot in 1997, but now they see dozens of spots around the ring. Only Hubble can see the individual bright spots. In the next few years, the entire ring will be ablaze as it absorbs the full force of the crash. The glowing ring is expected to become bright enough to illuminate the star's surroundings, providing astronomers with new information on how the star expelled material before the explosion.

The pink object in the center of the ring is debris from the supernova blast. The glowing debris is being heated by radioactive elements, principally titanium 44, created in the explosion. The debris will continue to glow for many decades.

The origin of a pair of faint outer red rings, located above and below the doomed star, is a mystery. The two bright objects that look like car headlights are a pair of stars in the Large Magellanic Cloud. The supernova is located 163,000 light-years away in the Large Magellanic Cloud.

The image was taken in December 2006 with Hubble's Advanced Camera for Surveys.

Object Name: SN 1987A

Image Type: Astronomical

Credit: NASA, ESA, P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)

Source: HubbleSite - Newsdesk

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Hubble Images Chronicle the Inner Ring's Light Show

News Release Number: STScI-2007-10

ABOUT THIS IMAGE:

This photo album of images from NASA's Hubble Space Telescope shows a ring of gas beginning to glow around an exploded star.

The stellar blast, called Supernova 1987A, was first spotted 20 years ago. The explosion is one of the brightest supernova blasts in more than 400 years. Hubble began watching the blast's aftermath shortly after it was launched in 1990.

The growing number of bright spots on the ring was produced by an onslaught of material unleashed by the blast. The shock wave of material is slamming into the ring's innermost regions, heating them up, and causing them to glow. The ring, about a light-year across, was probably shed by the star about 20,000 years before the star exploded.

Astronomers detected the first bright spot in 1997, but now they see dozens of spots around the ring. Only Hubble can see the individual bright spots. In the next few years, the entire ring will be ablaze as it absorbs the full force of the crash. The glowing ring is expected to become bright enough to illuminate the star's surroundings, providing astronomers with new information on how the star expelled material before the explosion.

The bright spot that appears to be on the ring at lower right is actually a foreground star. Supernova 1987A is 163,000 light-years away in the Large Magellanic Cloud.

The images were taken between 1994 and 2006 with Hubble's Wide Field Planetary Camera 2 and Advanced Camera for Surveys.

Object Name: SN 1987A

Image Type: Astronomical

Credit: NASA, ESA, P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)

Source: HubbleSite - Newsdesk

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Inner Debris of the Supernova 1987A Ring

News Release Number: STScI-2007-10

Object Name: SN 1987A

Image Type: Illustration/Artwork

Illustration Credit: NASA, ESA, and A. Feild (STScI)

Credit: NASA, ESA, P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)

Source: HubbleSite - Newsdesk

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Evolution of Supernova 1987A

News Release Number: STScI-2007-10

Object Name: SN 1987A

Image Type: Illustration/Artwork

Credit: NASA, ESA, and A. Feild (STScI)

Source: HubbleSite - Newsdesk