Where do supernovae come from?

September 17, 2010
A false-color X-ray image of the type Ia supernova remnant, Tycho. Credit: NASA/CXC/Rutgers/J.Warren & J.Hughes

(PhysOrg.com) -- Supernovae, the explosive deaths of massive stars, are among the most momentous events in the cosmos because they disburse into space all of the chemical elements that were produced inside their progenitor stars, elements essential for making planets and life. One class of supernovae (type Ia) provide yet another benefit: they are thought to be "standard distance candles," and are used by astronomers to estimate the distances to remote galaxies whose supernovae appear faint because they are far away; thus they can calibrate the cosmic distance scale.

If an old star which has finished burning its nuclear fuel is less massive than about 1.4 solar masses, its gravity is not strong enough to collapse it against the pressure of its atomic ashes, and it lingers on, gradually cooling down over billions of years. If however enough outside material falls onto the star, perhaps from a companion star, to increase its mass above the limit of 1.4 solar masses, gravity will prevail and suddenly convert it into a type Ia supernova. (Even more also become , but of other types -- they also seed the universe but are less reliable as standard candles.)

One of the outstanding puzzles in supernova research is the nature and role of the companion star that tips the mass balance and turns its neighbor into a cataclysm. Are these companion stars sometimes (always?) normal stars, or might they too be clumps of atomic ash that are gradually cooling off? And how does the in-falling matter manage to accumulate onto the neighboring star rather than just blow off as a puff of wind? Most disturbingly, why are putative companions and the effects they produce typically not seen at X-ray wavelengths where they are expected to be bright?

SAO astronomer Rosanne Di Stefano has been investigating these and related questions in a series of papers on type Ia supernovae. Writing in last month's , she shows that a star on the edge of becoming a supernova, having almost 1.4 solar masses, evolves with its companion in a complex way that is only occasionally detectable in X-rays. Whatever the nature of the companion star, there should be long intervals between episodes of X-ray brightness. Her results offer a convincing explanation for the absence of X-ray detections.

Explore further: Watching a Supernova Come and Go

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4 comments

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omatumr
1.7 / 5 (6) Sep 17, 2010
I suspect that supernovae come from the violent release of energy generated by neutron repulsion in the core of the star.

See: "Attraction and repulsion of nucleons: Sources of stellar energy" [J. Fusion Energy 19, 93-98 (2001)]; "Nuclear systematics: III. The source of solar luminosity", J. Radioanal. Nucl. Chem. 252, 3-7 (2002)]; "The standard solar model versus experimental observations" Proc. Third International Conference on Beyond Standard Model Physics - BEYOND 2002 (IOP, Bristol, editor: H. V. Klapdor-Kleingrothaus) 307-316 (2003)]; "Neutron repulsion confirmed as energy source", J. Fusion Energy 20, 197-201 (2003)].

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
ThanderMAX
Sep 17, 2010
This comment has been removed by a moderator.
TheWalrus
not rated yet Sep 17, 2010
"...they disburse into space all of the chemical elements..."

The word is "disperse." "Disburse" means "to pay."
omatumr
3 / 5 (1) Sep 17, 2010
See also the news story posted here on 16 Sept by Kitta MacPherson:

"3-D Computer Simulations Help Envision Supernovae Explosions" (w/ Video)

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