Supernova May Turn Stars Inside Out

Credit: Illustration: NASA/CXC/M.Weiss; X-ray: NASA/CXC/GSFC/U.Hwang & J.Laming

Like a child learning to take off his clothes, some supernovae events may turn stars inside out.  According to a recent release in the “Astrophysical Journal “, Una Hwang of Goddard Space Flight Center and Johns Hopkins University, and (John) Martin Laming of the Naval Research Laboratory revealed their findings from an X-ray study of an exploded star – Cassiopeia A.  Through the use of Chandra, they were able to document the distribution of the elements in this ancient supernova remnant with incredible accuracy.  This type of study reveals the location of different layers of the pre-supernova star some three centuries after its cataclysmic event and furthers our understanding of its nature.

In the accompanying artist’s conception, the left-hand panel demonstrates the inner layers of Cas A prior to its explosion.  The color array shows the majority concentrations of varied elements:  the iron core in blue, the lay of sulfur and silicon in green, and magnesium, neon and oxygen represented by red.  In the right-hand panel is the image from NASA’s Chandra X-ray Observatory which utilizes the same color scheme to represent the elemental distribution in the supernova remnant.  While some distributions are nearly identical – others are not.  The change in oxygen is explained by its difficulty to be detected in the X-ray spectrum because of absorption and the stripping of its electrons, but iron distribution is a real eye-opener.

By using the illustration as a comparison, the Chandra element map points to the fact that the majority of the star’s iron content was originally located at the core – but now lay on the outer fringes of the remnant.  To make matters even more mysterious, there is no evidence from Chandra’s X-ray findings, nor the Spitzer Space Telescope’s infrared observations, to show that iron might be located in the center of the Cas A remnant.  Need more proof that this star may have been flipped inside out?  Then take a look at silicon, sulfur and magnesium.  They are now located at the outer edges of the still-expanding debris cloud.  This unusual distribution of elements clearly indicates the explosion process wasn’t stable and the star turned inside out!

This new information adds to previous Chandra observations and provides the most detailed mapping of X-ray sources in Cas A – or any other massive star – to date.  It is incorporated from a million seconds of Chandra observing time and scientists conclude the X-ray emitting debris to have a mass about three times great than our Sun.  During the research, astronomers found “clumps of almost pure iron” – a precursor of supernova event caused by nuclear reactions.  “That such pure iron should exist was anticipated because another signature of this type of nuclear reaction is the formation of the radioactive nucleus titanium-44, or Ti-44. Emission from Ti-44, which is unstable with a half-life of 63 years, has been detected in Cas A with several high-energy observatories including the Compton Gamma Ray Observatory, BeppoSAX, and the International Gamma-Ray Astrophysics Laboratory”.

Credit: Tammy Plotner




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