The Fermi gamma-ray space telescope has discovered around 300 rapidly spinning neutron stars. Each of the newfound objects sweep two beams of radiation across the universe like a cosmic lighthouse.
These neutron stars are known to spin a whole lot of times per second and are specifically called millisecond pulsars; prior to the launch of Fermi in 2008, humanity was aware of lower than ten examples of such bodies. They’re particularly of note because they blast out a type of high energy electromagnetic radiation generally known as gamma-rays. Furthermore, inside this clutch of never-before-seen neutron stars are several so-called “spider pulsars,” that are believed to devour their companion stars (any stars locked in orbit with them) like black widow spiders devour their mates.
“We now have been very enthusiastic about what number of millisecond pulsars we now have been in a position to detect using these gamma rays,” Naval Research Laboratory astrophysicist Matthew Kerr said in an announcement. “These high-speed millisecond pulsars at the moment are a few of nature’s most precise timekeepers.”
By “timekeepers,” Kerr is referring to how the precise periodic rotation of millisecond pulsars means they may be used as timing mechanisms for deep space events. They effectively function cosmic clocks, exhibiting what are generally known as “pulsar timing arrays.”
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Like all neutron stars, rapidly spinning millisecond pulsars are born when massive stars reach the top of their fuel supply used for nuclear fusion. This puts a stop to energy flowing out from the cores of stars — energy that has helped supported them from the inward force of their very own gravity for billions of years.
The outer material of those dying stars then gets blown away in a large supernova explosion while their cores, which have masses between one and two times that of the sun, are crushed all the way down to the width of around 12 miles (20 kilometers). Within the wake of the star’s destruction, a neutron star is typically born.
The unique star’s size-reduction generates the acute characteristics we discover in neutron stars, like neutron-rich matter so dense a tablespoon of it could weigh 1 billion tons on Earth; magnetic fields so intense they blast out beams of gamma-rays Fermi can detect as periodic pulses. The rapid reduction in diameter also hurries up the neutron star’s spin, akin to an ice skater drawing of their arms to twirl faster.
As they age, neutron stars decelerate. In turn, their magnetic fields weaken, they usually begin to spin slower. Yet, when these exotic dead stars exist in a binary system, they’re able to getting a second wind.
“We’re in a position to study these objects that began as young pulsars in a binary system,” Kerr said. “Like a spinning top, they eventually slowed down and have become inert. Over the past a whole lot of hundreds of thousands of years, their binary companions dumped matter onto them, causing their speed to extend again, very dramatically and much faster than before, ‘recycling’ these pulsars into millisecond pulsars.”
Hunting cosmic spiders
One fascinating aspect of those recent pulsar discoveries is the actual fact a lot of them are “spider pulsars.” These neutron stars are named as such because, like post-copulation black widows, they devour their binary companion stars.
“Spider pulsars are named after arachnids that eat their smaller mates,” Megan DeCesar, discovery team member and a scientist at George Mason University, said within the statement. “Something similar can occur when a neutron star and its binary companion are very close to one another, and the millisecond pulsar ‘recycling’ process gets slightly carried away.
“The extraordinary radiation and particle wind from the pulsar eats away on the surface of the opposite star, leading to a puffball of evaporated material.”
Fermi is best at spotting these spider pulsars than other radio telescopes because radio waves from the neutron stars are sometimes blocked when pulsar beams omit the stays of devoured stars. High-energy gamma rays (Fermi’s specialty) are nevertheless able to penetrating the stellar wreckage.
“While it could be that spider systems are also intrinsically brighter in gamma rays, studying them will help us to grasp their origins and the bonanza of discoveries we now have made with Fermi,” said DeCesar.
The way to use a cosmic clock
One recent example of millisecond pulsars getting used as precise cosmic clocks was with the measurement of tiny time fluctuations brought on by the passage of low-frequency gravitational waves — tiny ripples in spacetime launched by distant black hole mergers and neutron star collisions.
“These are such exciting results,” Thankful Cromartie, National Research Council Research Associate on the Naval Research Laboratory ,said within the statement. “These low-frequency gravitational waves allow us to look into the centers of massive galaxies and higher understand how they were formed.”
Pulsar timing arrays may be utilized in the long run for navigation purposes, with rapidly spinning neutron stars playing the role of cosmic GPS systems for guidance beyond the surface of Earth. To do that, nevertheless, researchers might want to constrain the steadiness of such pulsars, something this discovery could help with.
A paper concerning the 300 recent neutron stars was published on Nov. 27 in the Astrophysical Journal.