Name: ScienceCasts: Why Won't the Supernova Explode?
Uploaded: 2014-05-06T14:36:14.000Z
Duration: 4 min 31 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Why Won't the Supernova Explode? Presented by Science@NASA

a massive star is about to die a spectacular death.

the star begins to collapse under its own tremendous weight.

Crushing pressure triggers new nuclear reactions,

setting the stage for a terrifying blast.

At least that's what supercomputers have been telling astrophysicists for decades.

Many of the best computer models of supernovas

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.

scientists need to examine the inside of a real supernova

So instead, they examine the remnant of the exploded star

Harrison and colleagues have figured out how to do this

the Nuclear Spectroscopic Telescope Array-"NuSTAR" for short.

on board a Pegasus XL rocket dropped from an airplane high above the Pacific Ocean,

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.

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

scientists might be able to figure out what's wrong with their computer simulations.

NuSTAR needs to be able to focus very high energy X-rays.

and when it decays it releases photons with an energy of 68 thousand electron volts.

such as NASA's Chandra X-Ray Observatory,

can focus X-rays only up to about 15 thousand electron volts.

Glass bends X-rays only a miniscule amount-

X-ray telescopes are an entirely different kind of telescope

They look a bit like the layers of a cylindrical onion.

Incoming X-rays pass between these layers,

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.'

NuSTAR will also study black holes, blazars, pulsars,

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