by A fast-spinning neutron star that sweeps beams of radiation across the universe like a cosmic beacon has been discovered by US Naval Laboratory (NRL) Remote Sensing Division intern Amaris McCarver and a team of astronomers.
The rapidly spinning neutron star, or “pulsar,” is located within the compact star cluster Glimpse-CO1, which sits in the galactic plane of the Milky Way about 10,700 light-years from Earth. This millisecond pulsar, spinning hundreds of times per second, is the first of its kind found in the Glimpse-CO1 star cluster. The pulsar, designated GLIMPSE-C01A, was spotted by the Very Large Array (VLA) on February 27, 2021, but remained buried in a vast amount of data until McCarver and his 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 arrays of pulsars can be used as cosmic timepieces. These arrays are so precise that they can be used to measure the infinitesimal squiggles and squishes caused by ripples in space and time known as gravitational waves. One possible practical application of this is the foundation of a “celestial GPS” that can be used for space navigation.
McCarver and her team discovered the object while examining images from the VLA’s Ionosphere 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 so successful,” McCarver, one of 16 interns in the Radio Optical Sensors Branch, Infrared at NRL DC, said in a statement.
Dead stars of the universe
Like all neutron stars, millisecond pulsars are born when stars with masses greater than about eight times that of the Sun reach the end of their lives. When their supplies of fuel needed for nuclear fusion are exhausted, the outward energy that supports these stars against the inward push of their own gravitational pull ceases.
This causes the cores of these stars to collapse and trigger shock waves in the star’s outer layers, causing most of its mass to be lost in massive supernova explosions.
The compressed stellar core squeezes electrons and protons together, creating a sea of neutrons, which are neutral particles normally found locked in atomic nuclei alongside positively charged protons. This neutron rich soup is so dense that if a tablespoon of it were brought to Earth, it would be more than 1 billion tons. That’s heavier than the largest mountain on our planet, Mount Everest (ironic, because this pulsar was found under a mountain of data).
The creation of a solar-mass neutron star about 12 miles (20 kilometers) across has other extreme consequences. Thanks to the conservation of angular momentum, the rapid decrease in radius of a dead stellar core accelerates its rotation. This is the cosmic equivalent of an ice skater pulling in their arms to increase their spin speed, but on a completely different level that allows some neutron stars to achieve rotational speeds as high as 700 spins per second.
Millisecond pulsars can also get a speed boost by removing material from a close companion star – like a cosmic vampire. This matter also has angular momentum.
The birth of a neutron star also sets up magnetic field lines, generating some of the most powerful magnetic fields in the universe.
These field lines send charged particles to the poles of the rapidly spinning pulsars, from which they are blasted out as jets. These jets carry beams of electromagnetic radiation that can periodically point at Earth as they sweep around with the rotation of a pulsar. This is responsible for how the pulsar appears to brighten periodically. The name “pulsar” actually refers to the fact that, upon their initial discovery by Jocelyn Bell Burnell on November 28, 1967, scientists thought these extreme dead stars were pulsating stars.
After finding GLIMPSE-C01A in massive amounts of data from the VLA, the team confirmed its existence by reprocessing archival sky survey data from the Robert C. Byrd Green Bank Telescope.
“This research shows how we can use radio brightness measurements at different frequencies to effectively find new galaxies, and that available sky surveys combined with the mountain of VLITE data mean that these measurements are essentially always available ,” Tracy E. Clarke, an astronomer with the NRL Remote Sensing Division, said in the statement. “This opens the door to a new era of searching for highly dispersed and highly accelerated pulsars.”
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“Millisecond pulsars offer a promising means of autonomously launching spacecraft from low Earth orbit into interstellar space, independent of ground contact and GPS availability,” Emil Polisensky, an astronomer with the NRL’s Remote Sensing Division added in the statement. “The confirmation of a new Millisecond pulsar identified by Amaris demonstrates the exciting potential for discovery with the NRL’s VLITE data and the central role that student interns play in cutting-edge research.”
The team’s research was detailed in a paper published on June 27 in The Astrophysical Journal.
Editor’s Update 7/5: The newly discovered pulsar sits 10,700 light years away. This article has been updated to reflect that.
