A fast-spinning neutron star that beams radiation across the universe like a cosmic beacon has been discovered by US Naval Research Laboratory (NRL) Remote Sensing Division intern Amaris McCarver and a team of astronomers.
The fast-spinning neutron star, or “pulsar,” is located in the dense star cluster Glimpse-CO1, which lies in the galactic plane of the Milky Way about 10,700 light-years from Earth. This millisecond pulsar, which spins hundreds of times per second, is the first of its kind discovered in the Glimpse-CO1 star cluster. The Very Large Array (VLA) spotted the pulsar, which is designated GLIMPSE-C01A, on February 27, 2021, but it remained buried in a huge amount of data until McCarver and colleagues discovered it in the summer of 2023.
Not only do the extreme conditions of these neutron stars make them ideal laboratories for studying physics in conditions found nowhere else in the universe, but their ultra-precise timing also means that pulsar arrays can be used as cosmic clocks. These arrays are so precise that they can be used to measure the infinitesimal squashing and squeezing caused by passing waves in space and time called gravitational waves. One possible practical application of this is the basis of a “celestial GPS” that could be used for space navigation.
McCarver and her team discovered the object while examining images from the VLA’s Low Frequency Ionospheric and Transient Experiment (VLITE) to search for new pulsars in 97 star clusters.
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“It was exciting so early in my career to see a speculative project work so successfully,” McCarver, one of 16 interns in the Radio, Infrared and Optical Sensors branch at NRL DC, said in a statement.
The dead stars of the universe
Like all neutron stars, millisecond pulsars are born when stars with a mass of about eight times that of the Sun reach the end of their lives. Once their stores of fuel needed for nuclear fusion are exhausted, the outward energy that sustains these stars against the inward pressure of their own gravitational pulls ceases.
This causes the cores of these stars to collapse and set off shock waves in the stars’ outer layers, causing most of their mass to be ejected in massive supernova explosions.
A compressing stellar core crushes electrons and protons together, creating a sea of neutrons, which are neutral particles normally found locked in atomic nuclei along with positively charged protons. This neutron-rich soup is so thick that if a tablespoon of it were brought to Earth, it would weigh over 1 billion tons. This is heavier than the largest mountain on our planet, Mount Everest (ironic, since this pulsar was discovered under a mountain of data).
Creating a neutron star with the mass of the sun crammed into a width of about 12 miles (20 kilometers) has other extreme consequences. Due to the conservation of angular momentum, the rapid decrease in the radius of the dead stellar core accelerates its rotation. It’s the cosmic equivalent of an ice skater pulling their arms to increase their spin speed, but on a completely different level, allowing some neutron stars to reach spin speeds of up to 700 revolutions per second.
Millisecond pulsars can also get a speed boost by scavenging matter from a nearby star – like a space vampire. This matter also carries with it angular momentum.
The birth of a neutron star also forces magnetic field lines to converge, generating some of the most powerful magnetic fields in the universe.
These field lines direct the charged particles toward the poles of the rapidly rotating pulsars, from where they are shot out as jets. These jets are accompanied by beams of electromagnetic radiation that can periodically point toward Earth as they move around in a pulsar spin. This is responsible for the way the pulsar appears to glow intermittently. The name “pulsar” actually refers to the fact that when they were first discovered by Jocelyn Bell Burnell on November 28, 1967, scientists thought that these terminally dead stars were literally pulsating stars.
After discovering GLIMPSE-C01A in vast amounts of VLA data, the team confirmed its existence by reprocessing archival sky survey data from the Robert C. Byrd Green Bank Telescope.
“This research highlights how we can use radio brightness measures at different frequencies to efficiently find new pulsars, and that the available sky surveys combined with the mountain of VLITE data mean that these measurements are essentially always available,” Tracey E .Clark, an astronomer with the NRL’s Remote Sensing Unit, said in the statement. “This opens the door to a new era of searching for highly dispersed and highly accelerated pulsars.”
“Millisecond pulsars offer a promising method for autonomously navigating spacecraft from low-Earth orbit to interstellar space, independent of ground contact and GPS availability,” Emil Polisensky, also an astronomer in NRL’s Remote Sensing Division, added in the statement. “The confirmation of a new Millisecond pulsar identified by Amaris highlights the exciting potential for discoveries with NRL’s VLITE data and the key role student interns play in cutting-edge research.”
The team’s research is detailed in a paper published June 27 in The Astrophysical Journal.
Editor’s Update 7/5: The newly discovered pulsar is located 10,700 light years away. This article has been updated to reflect this.
