Dense as the sun but small as a city: the universe’s largest neutron star is found

At the end of a rather large star’s life, it explodes in a burst of light and energy known as a supernova. If its core is massive enough, it could collapse in on itself and form a black hole.

If not, it becomes what’s called a neutron star, according to

Astronomers using the National Science Foundation’s Green Bank Telescope in West Virginia think they’ve just found the largest one in the universe — thoughtfully named J0740+6620, according to a press release from the observatory.

“Neutron stars are as mysterious as they are fascinating,” Thankful Cromartie, a graduate student at the University of Virginia and the lead author on a paper about the discovery, said in the release.

“These city-sized objects are essentially ginormous atomic nuclei. They are so massive that their interiors take on weird properties.”

At 2.17 times the mass of the sun in a sphere less than 19 miles across (about the width of Charlotte, NC), the neutron star is nearing its limit of existence — literally, according to

“This measurement approaches the limits of how massive and compact a single object can become without crushing itself down into a black hole,” according to the observatory’s release.

Neutron stars are already the densest “normal” objects in the universe aside from black holes, but scientists don’t actually consider those normal, the release states.

A sugar-cube worth of neutron star is the equivalent of roughly 100 million tons on Earth, for reference — “or about the same as the entire human population,” according to scientists.

WVU physics professors Duncan Lorimer and Maura McLaughlin work with mostly grade school students at the Pulsar Search Collaboratory at the Green Bank Telescope. Photo by Scott Lituchy / West Virginia University Scott Lituchy West Virginia University

J0740+6620 was discovered 4,600 light-years from earth, according to a separate news release from West Virginia University. One light-year is a mere 6 trillion miles.

The interiors of neutron stars, much like black holes, is a big fat mystery to astronomers.

But the discovery of one so near “the limit of existence” could prove helpful in determining what happens inside and how very dense materials behave, according to

“Observing neutron stars in this way is kind of like using a laboratory in space to study nuclear physics,” Cromartie said, the science website reported.

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Hayley is a Real Time reporter at The Charlotte Observer covering breaking news and trending stories in the Carolinas. She also created the Observer’s unofficial bird beat (est. 2015) with a summer full of ornithological-related content, including a story about Barred Owls in love.