Supernovas Slosh Before Exploding
 
Feb. 19, 2014:  A longstanding mystery of astronomy, how supernovas explode,
might finally have been solved with the help of NASA's Nuclear Spectroscopic
Telescope Array (NuSTAR).  The high-energy X-ray observatory has mapped
radioactive material in the supernova remnant Cassiopeia A (Cas A).  The map
reveals how shock waves likely rip massive dying stars apart--by sloshing.
 
"Stars are spherical balls of gas, and so you might think that when they end
their lives and explode, that explosion would look like a uniform ball
expanding out with great power," said Fiona Harrison, the principal
investigator of NuSTAR at Caltech. "Our new results show how the explosion's
heart, or engine, is distorted, possibly because the inner regions literally
slosh around before detonating."
 
Harrison is a co-author of a paper about the results appearing in the Feb. 20
issue of Nature.
 
http://www.nasa.gov/jpl/nustar/pia17838/#.UwURyIWs8VA
 
In this false-color X-ray image of CAS A, blue traces the distribution of
radioactive titanium-44, which is produced in the heart of the supernova.  
How supernovas explode has been a mystery for a long time: video. When
researchers simulate supernova blasts using computers, as a massive star dies
and collapses, the main shock wave often stalls out and the star fails to
shatter. The latest findings strongly suggest the exploding star literally
sloshed around, re-energizing the stalled shock wave and allowing the star to
finally blast off its outer layers.
 
NuSTAR's target, Cas A, was created when a massive star blew up as a supernova
leaving a dense stellar corpse and its ejected remains. The light from the
explosion reached Earth a few hundred years ago, so we are seeing the stellar
remnant when it was fresh and young.
 
"With NuSTAR we have a new forensic tool to investigate the explosion," said
the paper's lead author, Brian Grefenstette of Caltech. "Previously, it was
hard to interpret what was going on in Cas A because the material that we
could see only glows in X-rays when it's heated up. Now that we can see the
radioactive material, which glows in X-rays no matter what, we are getting a
more complete picture of what was going on at core of the explosion."
 
http://www.nasa.gov/jpl/nustar/pia17846/#.UwUZrYWs8VA
 
NuSTAR has helped decide between two competing models of supernova explosions:
Jets vs. Sloshing. MoreNuSTAR is the first telescope capable of producing maps
of radioactive elements in supernova remnants. In this case, the element is
titanium-44, which has an unstable nucleus produced at the heart of the
exploding star. The NuSTAR map of Cas A shows titanium concentrated in clumps
at the remnant's center, which suggests a sloshing action.
 
The NuSTAR map also casts doubt on other models of supernova explosions, in
which the star is rapidly rotating just before it dies and launches narrow
streams of gas that drive the stellar blast. Though imprints of jets have been
seen before around Cas A, it was not known if they were triggering the
explosion. NuSTAR did not see the titanium, essentially the radioactive ash
from the explosion, in narrow regions matching the jets, so the jets were not
the explosive trigger.
 
"This is why we built NuSTAR," said Paul Hertz, director of NASA's
astrophysics division in Washington. "To discover things we never knew -- and
did not expect -- about the high-energy universe."
 
Credits:
Production editor: Dr. Tony Phillips | Credit: Science@NASA
 
More information:
Why Won't the Supernova Explode?  -- this ScienceCast video explores the
longstanding mystery of supernova explosions
 
Supernovas seed the universe with many elements, including the gold in
jewelry, the calcium in bones and the iron in blood. While small stars like
our sun die less violent deaths, stars at least eight times as massive as our
sun blow up in supernova explosions. The high temperatures and particles
created in the blast fuse light elements together to create heavier elements.
Learn more
 
NuSTAR home page:
http://tinyurl.com/kaq8w66
 
 
Regards,
 
Roger

--- D'Bridge 3.99
 * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)