I feel dense just looking at this!

I feel dense just looking at this!

Originally shared by John Bowdre

Neutron stars are fascinating.

This cool infographic provides a visual approximation of their incredible density (hint: smash 500,000 Earths into a sphere ~20km across and you'll be close), but their story is actually even more interesting than that.

Neutron stars are born, so to speak, from the supernova death and subsequent gravitational collapse of a large star with 10-30 times the mass of our sun. That gravitational collapse squeezes the core of the star tighter and tighter - beyond the density found in a white dwarf star, to that found in atomic nuclei.

At its surface, the neutron star is composed of ordinary atomic nuclei (likely iron) crushed together into a solid lattice, with a sea of electrons flowing through the gaps between them. Deeper down, the nuclei hold ever-increased numbers of neutrons - so many that the usual nuclear forces would not be enough to hold the nuclei together. Only the absolutely insane gravitational force is able to hold the neutrons together in this configuration. (If you could, hypothetically, scoop up a teaspon of this stuff, it would not only weigh 900 times as much as the Great Pyramid of Giza, but also (more problematically) explode apart with such force that it would obliterate the unfortunate planet you attempted to weigh a chunk of neutron star on. Whoops!)

Of course, the rules of the universe do still apply to neutron stars. Stars rotate (our sun rotates once every ~24.5 days), and when the core of a massive star compresses and collapses into a neutron star it retains most of its angular momentum. You've seen a figure skater pull their arms in toward their body and thus spin faster? The same applies here: as the mass of the core pulls in tighter, it reduces the star's radius (and thus its moment of inertia) causing the neutron star to spin incredibly fast - often several hundred times per second.

Neutron stars are generally detected from their electromagnetic radiation, which is thought to be caused by particle acceleration near the neutron star's magnetic poles. Those poles aren't necessarily aligned with the neutron star's rotational axis, resulting in a directional beam of radio waves and other radiation. And, remember, these things are spinning fast, sweeping that beam across the universe like a rotating red or blue light atop an old police car. When seen from Earth, such beaconing neutron stars appear to rapidly pulse - which is why they get called pulsars.

This is seriously cool stuff! Be sure to dip into the linked Reddit thread to learn more about these incredible objects.

(h/t Jason England)
https://www.reddit.com/r/space/comments/5a0xad/just_made_a_visual_representation_on_how_dense/