Amaris McCarver, an intern in the Remote Sensing Division at the U.S. Naval Research Laboratory (NRL), and a team of astronomers have discovered a rapidly spinning neutron star that is emitting beams of radiation like a lighthouse across the universe.
The rapidly spinning neutron star, or “pulsar,” is located within the dense star cluster Glimpse-CO1, located about 10,700 light-years from Earth in the galactic plane of the Milky Way. Spinning hundreds of times per second, the millisecond pulsar is the first of its kind found in the Glimpse-CO1 star cluster. The Very Large Array (VLA) detected the pulsar, called GLIMPSE-C01A, on Feb. 27, 2021, but it remained buried under a vast amount of data until McCarver and his 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 in conditions found nowhere else in the universe, but their ultra-precise timing means that pulsar arrays could be used as cosmic clocks. So precise are these arrays that they could be used to measure ripples in space and time, the infinitesimally small squeezing and squeezing that occurs as gravitational waves pass through. One possible practical application is as the basis for a “celestial GPS” that could be used for space navigation.
McCarver and his team found this object while examining images from the VLA’s Low-Band Ionosphere and Transit Experiment (VLITE) to search for new pulsars in 97 star clusters.
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“It was exciting to see a speculative project so early in my career come to such a successful conclusion,” McCarver, one of 16 interns in the Radio, Infrared, Optical Sensors Branch in 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. Once the fuel supply for nuclear fusion is exhausted, the outward energy that supports these stars against the inward push of their own gravity ceases.
This causes the cores of these stars to collapse, triggering shock waves in the stars’ outer layers, which result in most of their mass being lost in massive supernova explosions.
The compressed stellar core crushes electrons and protons together, creating a sea of neutrons. Neutron seas are usually found locked in atomic nuclei alongside positively charged protons. This neutron-rich soup is so dense that a tablespoon of it brought to Earth would weigh over 1 billion tons. That’s heavier than Mount Everest, the largest mountain on our planet (ironic that this pulsar is located under a mountain of data).
The creation of a neutron star, where the mass of the sun is compressed into a width of about 12 miles (20 kilometers), has other extreme consequences. Thanks to the conservation of angular momentum, the rapid decrease in radius of a dead star’s core speeds up its rotation. This is the cosmic equivalent of an ice skater pulling in her arms to increase her rotation speed, but it’s on a whole different level, with some neutron stars reaching rotation speeds as great as 700 rotations per second.
Millisecond pulsars can also gain a boost in speed by stripping matter from a nearby companion star, like a cosmic vampire. This matter carries angular momentum with it.
The birth of a neutron star also forces magnetic field lines towards each other, creating some of the strongest magnetic fields in the universe.
These field lines direct charged particles to the poles of rapidly spinning pulsars, from where they are ejected in jets. These jets are accompanied by beams of electromagnetic radiation that can periodically point toward Earth as they spread outward along with a pulsar’s spin. This is what causes the pulsar to periodically shine. The name “pulsar” actually refers to the fact that when it was first discovered by Jocelyn Bell Burnell on November 28, 1967, scientists thought that these extremely 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 survey data from the Robert C. Byrd Green Bank Telescope.
“This research highlights how we can use radio brightness measurements at different frequencies to efficiently find new pulsars, and how combining existing sky surveys with the VLITE data mountain means these measurements have essentially always been available,” says Tracy E. Clarke, an astronomer in the NRL Remote Sensing Division. “This opens the door to a new era of searching for highly dispersed and highly accelerating pulsars.”
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“Millisecond pulsars offer a promising method for autonomously navigating spacecraft from low Earth orbit into interstellar space, independent of ground contact and GPS availability,” added Emil Polisensky, astronomer in the NRL Remote Sensing Division. “Confirmation of a new millisecond pulsar identified by Amaris highlights the exciting discovery potential 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 10,700 light-years away. This article has been updated to reflect this.