* Astronomy

Dust clouds glow thanks to delayed "light echoes" from a supernova, 400 years after light from the original event washed over Earth
(Images: X-ray: NASA/CXC/Rutgers/J Warren/J Hughes; Optical light echo: NOAO/AURA/NSF/Harvard/A Rest et al; LMC image: NOAO/AURA/NSF/S Points/C Smith/MCELS team)

Light radiating outwards from a supernova hits dust clouds along the way and is reflected towards Earth, providing a delayed echo or "replay" of the original explosion.
Credit: NASA/CXC/M.Weiss

Credit: NASA/CXC/NCSU/K.J.Borkowski et al.
JPEG (198.1 kb)	Tiff (15.5 MB)	PS (6 MB)

This Chandra X-ray Observatory image shows the debris of a massive star explosion in the Large Magellanic Cloud, a small galaxy about 160,000 light years from Earth. The supernova remnant (SNR) shown here, N132D, is the brightest in the Magellanic clouds, and belongs to a rare class of oxygen-rich remnants. Most of the oxygen that we breathe on Earth is thought to have come from explosions similar to this one.
The colours in this image show low energy X-rays (red), intermediate energy X-rays (green) and high energy X-rays (blue). Substantial amounts of oxygen are detected in this image, particularly in the green regions near the centre of the image. The location of these oxygen-rich areas, detected in the Chandra image, is generally well matched with the oxygen-rich areas detected in Hubble Space Telescope images (not shown here). However, the expanding, ellipse-shaped shell of oxygen seen in N132D is not seen in either G292.0+1.8 or Puppis A, two oxygen-rich SNRs in the galaxy with similar ages to N132D (about 3,000 years, ten times older than Cas A). The origin of this shell is unknown, but it might have been created by a `nickel bubble' shortly after the supernova explosion, caused by radioactive energy input from nickel that was created by the explosion. The existence of such bubbles is predicted by theoretical work.

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North Carolina State University astrophysicists have answered a long-standing question about the nature of one of our galaxy’s most famous supernova explosions, discovering a new class of supernova in the process.
Dr. Stephen Reynolds, astrophysicist in NC State’s College of Physical and Mathematical Sciences, along with colleague Dr. Kazik Borkowski and a team of scientists from NASA, Rutgers University, and the Naval Research Laboratories, set out to determine whether the Kepler supernova, which occurred in 1604 A.D., was a core collapse supernova or a thermonuclear supernova.
They revealed their results in a press conference today at the annual meeting of the American Astronomical Society.

A core collapse supernova occurs when a single, massive star (with a mass eight times greater – or more – than that of our sun) reaches the end of its life and explodes. Core collapse supernovae leave pulsars, rapidly spinning neutron stars, behind when they occur. They also tend to be surrounded by circumstellar medium – leftover elements from the star that collapsed, as well as large amounts of oxygen and small amounts of iron. These supernovae are usually located near “star-forming” sites along a galaxy’s edge.
Thermonuclear, or Type Ia, supernovae occur when a white dwarf star, which typically travels through space with a companion star that eventually “leaks” its own mass onto the dwarf, reaches its mass limit and explodes. These supernovae can be found all over a galaxy, are typically not associated with any circumstellar medium, and produce large amounts of iron.
The Kepler supernova has long puzzled scientists because it has features that are common to both types of supernova: The Kepler supernova’s location and the presence of a lot of iron are indicative of a Type Ia supernova, but the dense surroundings and nitrogen-enriched circumstellar medium are commonly associated with the aftermath of a core collapse.
Reynolds and his team used the powerful Chandra X-ray telescope to observe the Kepler supernova, and they discovered that Kepler is something entirely new: a Type Ia supernova in which the progenitor of the white dwarf star that created it had enough mass to create circumstellar medium.

“We really don’t know much about Type Ia supernovae, and they’re really important to our understanding of the universe. We use the fact that they all have similar luminosities, or brightness, to calculate the distance of galaxies and to determine how much and how quickly the universe is expanding. Type Ia’s are also the source of the majority of iron in the universe, and can give us a lot of information about its chemical history. A new class of Type Ia supernova will have huge implications for our ability to understand the source of the elements that create our universe” - Dr. Stephen Reynolds.

Source:      North Carolina State University

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. The image 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.


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

Position (2000): RA 05h 34m 08.80s Dec -70º 34' 28.00"

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