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• On Aug. 6, 1967, Jocelyn Bell discovered a series of sharp pulses coming from a distant galaxy every 1.3 seconds. This “scruff” was an unknown type of astronomical object, later named a pulsar.
• A neutron star is the densest object made of ordinary matter, just a whisker away from a black hole. It is created when an ordinary star is sufficiently massive, eight to 15 times as massive as the sun, has exhausted all its nuclear fuel and collapses to extreme densities.
• Physicists think a neutron star is sort of like an egg, with a crust, an outer core, and an inner core. The outer crust is made of iron nuclei, the outer core is a liquid consisting mainly of neutrons, and the inner core is an enigma with matter different to neutrons and protons.
• To describe the squeezability of the inner core, physicists formulate a so-called equation of state. This equation of state relates density to pressure and predicts a certain relationship between the neutron star’s size and mass.
• Astronomers have a battery of techniques to measure the mass and radius of neutron stars. These include pulsar timing, studying how deformable neutron stars are when they collide, and studying the aftermath of a neutron star collision.
• The discoveries of neutron stars heavier than two solar masses indicate that the matter inside the inner core can’t be very jelly-like. Nuclear experiments and observations of gravitational waves, radio pulses, and X-rays are used to determine the equation of state.

Published February 24, 2023
Visit Nautilus to read Katia Moskvitch’s original post Giant Zombie Atoms of the Cosmos

• Miguel Aragon is a computational physicist at the National Autonomous University of Mexico, where he studies the large-scale structure of the universe, galaxy formation, machine learning, data mining, and visualization.
• The Milky Way is not special in itself, but its location is what makes it special. It is located near the center of a cosmological wall, a flat association of galaxies that forms a membrane between cosmological voids.
• The universe looks like a sponge, with cosmological walls, filaments, and clusters. Clusters are the densest parts of the universe, and walls are the least dense.
• The Milky Way is strangely large for living in a wall, and its velocity dispersion is 10 times lower than what is expected. This has been considered a mystery.
• Miguel Aragon has explored the possibility that the fact that the Milky Way is so massive in this wall may have helped the development of life.

Published February 7, 2023
Visit Nautilus to read Brian Gallagher’s original post What Makes the Milky Way Special?