Amaris McCarver, an intern at the U.S. Naval Research Laboratory’s (NRL) Remote Sensing Division, and a team of astronomers have discovered a rapidly spinning neutron star that is beaming radiation across the universe like a cosmic lighthouse.
The rapidly 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. The millisecond pulsar, which spins hundreds of times per second, is the first of its kind found in the Glimpse-CO1 star cluster. The Very Large Array (VLA) discovered the pulsar, designated GLIMPSE-C01A, on February 27, 2021, but it remained buried in a huge trove 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 to study physics in conditions not found anywhere else in the universe, but their ultra-precise timing also means that arrays of pulsars could be used as cosmic timekeepers. These arrays are so precise that they can be used to measure the infinitesimal squeezes and compressions caused by ripples in space and time called gravitational waves. One potential practical application of this is the basis for a “celestial GPS” that could be used for space navigation.
McCarver and her team discovered the object while studying images from the VLA’s Low-band Ionosphere and Transient Experiment (VLITE), which was looking for new pulsars in 97 star clusters.
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“It was exciting to see a speculative project turn into such a success so early in my career,” McCarver, one of 16 interns in the Radio, Infrared, Optical Sensors department at NRL DC, said in a statement.
The 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 ends of their lives. Once their fuel supplies needed for nuclear fusion are exhausted, the outward energy that supports these stars against the inward pressure of their own gravity ceases.
This causes the core of these stars to collapse and creates shock waves in the outer layers of the stars, releasing most of the mass of the stars in huge supernova explosions.
The squeezing stellar core crushes electrons and protons, creating a sea of neutrons, neutral particles normally found 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 weigh more than 1 billion tons. That’s heavier than the largest mountain on our planet, Mount Everest (ironic, considering that pulsar was found beneath a mountain of data).
The creation of a neutron star with the mass of the sun crammed into a width of about 12 miles (20 kilometers) has other extreme consequences as well. Thanks to the conservation of angular momentum, the rapid reduction in the radius of a dead stellar core speeds up its rotation. This is the cosmic equivalent of an ice skater pulling in his arms to increase the speed of his spin, but on a whole different level, allowing some neutron stars to reach spin rates of up to 700 revolutions per second.
Millisecond pulsars can also get a speed boost by stripping matter from a nearby star — like a cosmic vampire. This matter also carries angular momentum.
The birth of a neutron star also causes magnetic field lines to converge, creating one of the most powerful magnetic fields in the universe.
These field lines guide charged particles toward the poles of rapidly spinning pulsars, from where they are ejected as jets. These jets are accompanied by beams of electromagnetic radiation that can periodically point toward Earth as they drift around with the pulsar’s rotation. This is responsible for how the pulsar appears to periodically light up. The name “pulsar” actually refers to the fact that, when 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 large amounts of data from the VLA, the team confirmed its existence by reprocessing archival data from the Robert C. Byrd Green Bank Telescope.
“This research highlights how we can use radio brightness measurements at multiple frequencies to efficiently find new pulsars, and that available sky surveys combined with the wealth of VLITE data means that these measurements are potentially available forever,” Tracy E. Clarke, an astronomer in the NRL Remote Sensing Division, said in the statement. “This opens the door to a new era of searches for highly distributed 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,” added Emil Polisensky, also an astronomer in the NRL Remote Sensing Division, in the statement. “The confirmation of a new millisecond pulsar identified by Amaris highlights the exciting potential for discovery with NRL’s VLITE data and the key role that interns play in groundbreaking 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.