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Why Won't the Supernova Explode? Presented by Science@NASA
Somewhere in the Milky Way,
a massive star is about to die a spectacular death.
As its nuclear fuel runs out,
the star begins to collapse under its own tremendous weight.
Crushing pressure triggers new nuclear reactions,
setting the stage for a terrifying blast.
And then... nothing happens.
At least that's what supercomputers have been telling astrophysicists for decades.
Many of the best computer models of supernovas
fail to produce an explosion.
At the end of the simulation,
gravity wins the day and the star simply collapses.
Clearly, physicists are missing something.
'We don't fully understand how supernovas of massive stars work yet,'
says Fiona Harrison, an astrophysicist at the California Institute of Technology.
To figure out what's going on,
scientists need to examine the inside of a real supernova
while it's exploding -
not a particularly easy thing to do.
So instead, they examine the remnant of the exploded star
as soon after the explosion as possible.
Harrison and colleagues have figured out how to do this
using a new space telescope called
the Nuclear Spectroscopic Telescope Array-"NuSTAR" for short.
Launched on June 13, 2012,
on board a Pegasus XL rocket dropped from an airplane high above the Pacific Ocean,
NuSTAR is a Small Explorer satellite
that carries the first space telescope that can focus very high-energy X-rays.
NuSTAR will produce images roughly 100 times sharper
than those possible with previous high-energy X-ray telescopes.
When NuSTAR finishes its check-out and becomes fully operational,
scientists will use it to scan supernova remnants
for clues etched into the pattern of elements
spread throughout the explosion's debris.
'The distribution of the material in a supernova remnant
tells you a lot about the original explosion,' says Harrison.
An element of particular interest is titanium-44.
Creating this isotope of titanium through nuclear fusion
requires a certain combination of energy, pressure, and raw materials.
Inside the collapsing star,
that combination occurs at a depth that's very special.
Everything below that depth succumbs to gravity
and collapses inward to form a black hole.
Everything above that depth will be blown outward in the explosion.
Titanium-44 is created just above the cusp.
So the pattern of how titanium-44 is spread throughout a supernova remnant
can reveal a lot about what happened at that crucial threshold
during the explosion.
And with that information,
scientists might be able to figure out what's wrong with their computer simulations.
To detect titanium-44,
NuSTAR needs to be able to focus very high energy X-rays.
Titanium-44 is radioactive,
and when it decays it releases photons with an energy of 68 thousand electron volts.
Existing X-ray space telescopes,
such as NASA's Chandra X-Ray Observatory,
can focus X-rays only up to about 15 thousand electron volts.
Normal lenses can't focus X-rays at all.
Glass bends X-rays only a miniscule amount-
not enough to form an image.
X-ray telescopes are an entirely different kind of telescope
consisting of many concentric shells.
They look a bit like the layers of a cylindrical onion.
Incoming X-rays pass between these layers,
which guide the X-rays to the focus
by reflecting them off the surfaces of the shells.
The NuSTAR team has spent years perfecting delicate manufacturing techniques
required to make high-precision X-ray optics for NuSTAR
that work at energies as high as 79 thousand electron volts.
Their efforts could crack 'the mystery of the supernova that wouldn't explode.'
And that's just for starters.
NuSTAR will also study black holes, blazars, pulsars,
and many more exotic objects.
The high-energy Universe is about to come into sharper focus-
and no one can say what surprises may be in store.
For more explosive information about the cosmos, visit science.nasa.gov