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why won't the supernova explode

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somewhere in the milky way a massive

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star is about to die a spectacular death

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as its nuclear fuel runs out the star

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begins to collapse under its own

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tremendous weight

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crushing pressure triggers new nuclear

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reactions

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setting the stage for a terrifying blast

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and then

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nothing happens

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at least that's what supercomputers have

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been telling astrophysicists for decades

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many of the best computer models of

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supernovas fail to produce an explosion

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at the end of the simulation gravity

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wins the day and the star simply

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collapses

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clearly physicists are missing something

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we don't fully understand how supernovas

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of massive stars work yet says fiona

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harrison an astrophysicist at the

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california institute of technology

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to figure out what's going on

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scientists need to examine the inside of

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a real supernova while it's exploding

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not a particularly easy thing to do

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so instead they examine the remnant of

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the exploded star as soon after the

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explosion as possible

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harrison and colleagues have figured out

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how to do this using a new space

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telescope called the nuclear

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spectroscopic telescope array

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nustar for short

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launched on june 13th 2012 onboard a

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pegasus xl rocket dropped from an

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airplane high above the pacific ocean

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nustar is a small explorer satellite

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that carries the first space telescope

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that can focus very high energy x-rays

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nustar will produce images roughly 100

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times sharper than those possible with

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previous high-energy x-ray telescopes

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when nustar finishes its checkout and

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becomes fully operational scientists

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will use it to scan supernova remnants

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for clues etched into the pattern of

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elements spread throughout the

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explosion's debris

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the distribution of the material in a

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supernova remnant tells you a lot about

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the original explosion says harrison

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an element of particular interest is

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titanium 44.

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creating this isotope of titanium

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through nuclear fusion requires a

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certain combination of energy pressure

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and raw materials

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inside the collapsing star that

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combination occurs at a depth that's

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very special

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everything below that depth succumbs to

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gravity and collapses inward to form a

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black hole

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everything above that depth will be

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blown outward in the explosion

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titanium 44 is created just above the

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cusp so the pattern of how titanium 44

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is spread throughout a supernova remnant

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can reveal a lot about what happened at

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that crucial threshold during the

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explosion and with that information

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scientists might be able to figure out

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what's wrong with their computer

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simulations

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to detect titanium 44

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nustar needs to be able to focus very

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high energy x-rays

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titanium 44 is radioactive

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and when it decays it releases photons

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with an energy of 68 000 electron volts

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existing x-ray space telescopes such as

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nasa's chandra x-ray observatory can

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focus x-rays only up to about 15 000

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electron volts

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normal lenses can't focus x-rays at all

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glass bends x-rays only a minuscule

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amount not enough to form an image

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x-ray telescopes are an entirely

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different kind of telescope consisting

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of many concentric shells

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they look a bit like the layers of a

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cylindrical onion

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incoming x-rays pass between these

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layers which guide the x-rays to the

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focus by reflecting them off the

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surfaces of the shells

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the new star team has spent years

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perfecting delicate manufacturing

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techniques required to make

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high-precision x-ray optics for nustar

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that work at energies as high as 79 000

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electron volts

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their efforts could crack the mystery of

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the supernova that wouldn't explode

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and that's just for starters

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nustar will also study black holes

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blazars pulsars and many more exotic

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objects

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the high energy universe is about to

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come into sharper focus

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and no one can say what surprises may be

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in store