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Gravity always wins. As a star ages, a tug-of-war plays out in its core. Gravity pulls the star inward, while radiation from the nuclear reactions in the core push outward. It’s a struggle that can last for billions of years. But in the end, the star exhausts its nuclear fuel, the radiation stops, and the core collapses. Gravity wins.
For stars like the Sun, gravity squeezes out the space between atoms. The atoms themselves push against each other, though, so the collapse stops there. The result is a white dwarf - a star that’s roughly as massive as the Sun, but only as big as Earth.
But for stars that are a good bit heavier than the Sun, gravity doesn’t stop there. It squeezes so tightly that it smashes together protons and electrons to make neutrons. The neutrons are jammed so tightly that the stellar remnant is basically a big atomic nucleus moving through space.
Because it’s made of neutrons, this remnant is known as a neutron star. It’s a couple of times as massive as the Sun, but it’s squeezed so tightly that it’s only about as wide as Manhattan. At that density, a teaspoonful of its material would weigh as much as tens of millions of African elephants.
A newborn neutron star spins rapidly. It also has an extremely powerful magnetic field. The combination produces bright but short pulses of energy. So young neutron stars are also known as pulsars - flickering stellar remnants that have lost the fight with gravity.
More about neutron stars tomorrow.
Script by Damond Benningfield, Copyright 2013
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