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Text on screen: What is a neutron star?

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When a star bigger

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and more massive than the sun

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runs out of fuel at the end of its life,

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its core collapses while the outer

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layers are blown off in a

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supernova explosion

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What's left behind

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depends on the star's original mass.

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A star roughly 10 to

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20 times our sun

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leaves behind a neutron star.

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A more massive star

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becomes a black hole.

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Unlike black holes, neutron stars

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are directly observable, usually

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as pulsars - the lighthouses of the

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cosmos. Discovered

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50 years ago, they are the

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densest observable objects in the

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universe.

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Neutron stars compress up

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to twice the sun's mass into a 

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city-sized sphere. Matter is

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packed so tightly that a teaspoon

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of neutron star interior

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would weigh more than a billion tons

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on Earth.

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Still, the nature of the ultra-dense matter

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in the cores of neutron stars

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is unknown.

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Because neutron stars

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pack so much mass into such a

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tiny volume, they produce

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gravity strong enough to bend the light they emit,

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distorting their appearance in

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a way that enables the mass

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and size of the star to be measured.

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Scientists cannot

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reproduce the extreme conditions

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in and around neutron stars on

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Earth. They must look

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into the galaxy to answer decades-old

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questions about extreme matter and

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gravity.

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NASA's Neutron star Interior

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Composition Explorer mission,

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or NICER, will make X-ray

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observations of neutron stars from its

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perch on the International Space Station.

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It will give astronomers more

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insight into these mysterious

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objects - helping determine

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what is under their surface.

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A multipurpose

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mission, NICER includes a

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technology demonstration called SEXTANT.

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It will analyze NICER's

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observations to validate the use of

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rapidly rotating neutron stars

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as navigation beacons, for travel

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in deep space, throughout the solar

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system and beyond.

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Text on screen: nasa.gov/nicer