A fast-spinning neutron star that sweeps 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 rotating neutron star, or “pulsar,” is located within the dense star cluster Glimpse-CO1, which lies in the Milky Way’s galactic plane about 10,700 light-years from Earth. This millisecond pulsar, which rotates hundreds of times per second, is the first of its kind found 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 large amount of data until McCarver and colleagues found it in the summer of 2023.
Not only do the extreme conditions of these neutron stars make them ideal laboratories for studying physics under conditions found nowhere else in the universe, but their extremely precise timing also means that strings of pulsars can be used as cosmic clocks. These strings are so precise that they can be used to measure the infinitesimal strain and squeeze caused as ripples in space and time called gravitational waves. A possible practical application of this is the foundation of a “celestial GPS” that could be used for space navigation.
McCarver and her team found the object while probing images from the VLA’s Low Band 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 work so successfully,” McCarver, one of 16 interns in the Optical Radio Sensors Branch, Infrared, at NRL DC, said in a statement.
The dead stars of the universe
Like all neutron stars, millisecond pulsars are born when stars more than about eight times the mass of the Sun reach the end of their lives. Once their supplies of the fuel needed for nuclear fusion are exhausted, the external energy that supports these stars against the internal thrust of their gravitational pulls ceases.
This causes the cores of these stars to collapse and cause shock waves in the outer layers of the stars, resulting in most of their mass being poured out in massive supernova explosions.
The compact stellar core squeezes electrons and protons together, creating a sea of neutrons, which are neutral particles usually found locked in atomic nuclei along with positively charged protons. This neutron-rich soup is so dense 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, seeing as this pulsar was found under a mountain of data).
Creating a neutron star with the mass of the sun packed into a width of about 12 miles (20 kilometers) also has other extreme consequences. Thanks to the conservation of angular momentum, the rapid reduction of the radius of a dead stellar core accelerates its rotation. This is the cosmic equivalent of an ice skater drawing on their arms to increase their spin speed, but on a completely different level that allows some neutron stars to achieve spin speeds of up to 700 revolutions per second.
Millisecond pulsars can also get a speed boost by stripping matter from a nearby companion star – like a cosmic vampire. This matter also carries with it angular momentum.
The birth of a neutron star also forces magnetic field lines together, generating what are some of the most powerful magnetic fields in the universe.
These field lines channel charged particles to the poles of rapidly spinning pulsars, from where they explode as jets. These jets are accompanied by beams of electromagnetic radiation that can periodically direct from Earth as they move around with the spin of a pulsar. This is responsible for the way 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 that these extreme dead stars were literally pulsating stars.
After finding GLIMPSE-C01A in a large amount of data from the VLA, the team confirmed its existence by reprocessing archival sky observation data from the Robert C. Byrd Green Bank Telescope.
“This research highlights how we can use radio luminosity measurements at different frequencies to find new pulsars efficiently, and that the available sky observations combined with the mountain of VLITE data mean that those 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 research into highly dispersed and highly accelerated pulsars.”
“Millisecond pulsars offer a promising method for autonomous spacecraft navigation from low-Earth orbit into interstellar space, independent of ground contact and GPS availability,” Emil Polisensky, also an astronomer in the Remote Impact Division of the NRL. “Confirmation of a new millisecond pulsar identified by Amaris highlights the exciting potential for discovery with NRL’s VLITE data and the key role student interns play in cutting-edge research.”
The team’s research was 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 that.
