By Jonny Lupsha, Wondrium Staff Writer
Neutron stars are corpses of stars that have gone supernova. They’re incredibly dense and have one to three times the mass of the Sun. Scientists may have detected a new type of neutron star.
A slowly rotating, blinking star located 4,200 light years away has excited and perplexed scientists. Letting off huge bursts of energy approximately three times per hour, the star appears to be a new variation of neutron star called an “ultra-long period magnetar,” or highly magnetized neutron star that rotates much more slowly than its counterparts. Those counterparts, for comparison, appear to “blink on and off” within milliseconds.
After a star explodes in a supernova, it becomes a neutron star. In his video series The Life and Death of Stars, Dr. Keivan G. Stassun, Professor of Physics and Astronomy at Vanderbilt University, explains the unbelievable phenomenon that is the neutron star.
He Ain’t Heavy; He’s My Brother
“In the final stage of a massive star’s life, the star’s core, having fused all the way to iron, finally collapses under gravity, causing the atoms to completely dissociate into their constituent parts: protons, electrons, and neutrons,” Dr. Stassun said. “The protons and electrons come together to form additional neutrons so that pure neutrons are all that remain in the rapidly collapsing core. That ball of pure neutrons collapses to the point that it represents the densest form of matter known in the universe.”
When that happens, the outer layers of the star bounce off the core and explode as a supernova. Most of the star’s mass is expelled throughout the universe in the blast, but the core of pure neutrons remains as a neutron star. In most matter, individual atoms are widely separated by electromagnetic repulsion in their electrons. Without that, a neutron star is so dense that it’s denser than anything else in the universe, aside from a black hole.
A neutron star contains the mass of one to three Suns and is between 10 and 20 kilometers. In terms of density, it paints an unbelievable picture.
“Whereas water has a density of one gram per cubic centimeter, and iron has a density of about five grams per cubic centimeter, and the core of the Sun has a density of about 100 grams per cubic centimeter, a neutron star has a density of about 100 trillion grams per cubic centimeter,” Dr. Stassun said. “One sugar-cube-size chunk of a neutron star would weigh more than all the people who have ever lived.”
As Long as We Keep Spinning
The neutron star that scientists are currently observing spins so slowly that the existence of such a state has been theoretical until this point. Otherwise, neutron stars spin incredibly quickly. The slowest of them spin once per second, which is no small feat, considering they weigh as much as the Sun and are the size of a city. A more typical neutron star rotates 30 times per second, while the fastest spin up to a thousand times per second.
“This is a consequence of the law of conservation of angular momentum,” Dr. Stassun said. “That law, similar to the conservation of energy, says, in essence, that the spin energy of an object is also conserved. The way this works is that a large object spinning slowly is equivalent to a small object spinning rapidly—this is the very law of physics that explains how spinning ice skaters can spin so fast by pulling in their arms.”
When an ice skater goes into a spin, they extend their limbs, beginning big and slow. As they pull their arms and legs in more closely to their bodies, they become smaller, and the law of conservation of angular momentum forces them to speed up. This same simple physics works for ice skaters and neutron stars alike.
“A neutron star represents the highly collapsed, compressed remnant of a star that was a million times larger,” Dr. Stassun said. “That star may have spun relatively slowly, perhaps once per month or so, but now that initial spin—that slow initial spin—has been amplified a million fold due to the million-fold decrease in size.”
The possible ultra-long period magnetar will be officially confirmed or denied at a later date. For now, it retains the potential of becoming an exciting astronomical phenomenon of the modern age.