Amaris McCarver and a team of astronomers have discovered a rapidly rotating neutron star that spreads beams of radiation through space like a cosmic beacon.
The rapidly rotating neutron star, or “pulsar,” is located in the dense star cluster Glimpse-CO1, located in the galactic plane of the Milky Way about 10,700 light-years from Earth. Spinning hundreds of times per second, this millisecond pulsar is the first of its kind found in the Glimpse-CO1 cluster. The Very Large Array (VLA) spotted the pulsar, designated GLIMPSE-C01A, on February 27, 2021, but it remained buried in the massive 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 ultra-precise timing also means that pulsar fields can be used as cosmic timekeepers. These fields are so precise that they can be used to measure the infinitesimal squiggles and squiggles caused by ripples in space and time called gravitational waves. One possible practical application is the basis of a “celestial GPS” that can be used for space navigation.
McCarver and her team found the object while examining images from the VLA Low Band Ionosphere and Transition 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,” said McCarver, one of 16 interns in NRL DC’s Radio, Infrared, Optical Sensors Branch.
Dead stars of the universe
Like all neutron stars, millisecond pulsars are born when stars with masses greater than eight times the mass of the Sun reach the end of their lives. Once their stores of fuel needed for nuclear fusion are exhausted, the external energy that supports these stars against the internal pressure of their own gravitational forces ceases.
This causes the cores of these stars to collapse and trigger shock waves in the stars’ outer layers, causing most of their mass to be lost in massive supernova explosions.
A compressing stellar core crushes electrons and protons together, creating a sea of ​​neutrons, which are neutral particles usually found in atomic nuclei next to 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, since this pulsar was found under the mountain of data).
Creating a neutron star with the mass of the Sun packed 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. This is the cosmic equivalent of a skater drawing in their arms to increase their spin rate, but on a completely different level, allowing some neutron stars to spin at speeds of up to 700 revolutions per second.
Millisecond pulsars can also speed up by stripping matter from a nearby star – like a space vampire. This mass also carries with it a moment of momentum.
The birth of a neutron star also compresses magnetic field lines, creating some of the strongest magnetic fields in the universe.
These field lines direct charged particles to the poles of rapidly rotating pulsars, from where they are ejected as jets. These jets are accompanied by jets of electromagnetic radiation that can periodically point toward Earth as they move around the pulsar’s rotation. This is responsible for how the pulsar appears to periodically brighten. 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 extreme dead stars were literally stars that pulsate.
After finding GLIMPSE-C01A in the vast 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 shows how we can use radio luminosity measurements at different frequencies to effectively find new pulsars, and that the available sky surveys, combined with the mountain of VLITE data, mean that these measurements are essentially always available,” Tracy E. Clarke, Astronomer Division remote sensing NRL, she said in a statement. “This opens the door to a new era of searching for highly dispersed, highly accelerated pulsars.”
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“Millisecond pulsars offer a promising method for autonomous navigation of spacecraft from low Earth orbit into interstellar space, independent of ground contact and GPS availability,” Emil Polisensky, also an astronomer with the NRL Remote Sensing Division, added in a statement. “Confirmation of the new millisecond pulsar identified by Amaris highlights the exciting potential for discovery with the VLITE NRL 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.
Editorial Update 7/5: The newly discovered pulsar is located 10,700 light years away. This article has been updated to reflect this.