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Maura McLaughlin and Duncan Lorimer of WVU use the Green Bank Observatory for research purposes. Here, McLaughlin and Lorimer stand at the top of the Green Bank telescope, which has enabled them to detect the most massive neutron star ever created. CREDIT: Scott Lituchy / West Virginia University.
Researchers at the University of West Virginia helped uncover the most massive neutron star to date, discovering the Green Bank telescope in Pocahontas County.
The neutron star, called J0740 + 6620, is a fast-moving pulsar that packs 2.17 times the mass of the sun (333 000 times the mass of the Earth) in a sphere of 20 to 30 kilometers only. This measurement approaches the limits of the mass and compactness of a single object without becoming crushed by a black hole.
The star was detected about 4,600 light years from Earth. A light year is about six billion kilometers.
These results, from the NANOGrav Physics Frontiers Center, funded by the National Science Foundation, were published today (Sept. 16) in Nature Astronomy.
Duncan Lorimer, professor of astronomy and associate dean of research at Eberly College, College of Arts and Sciences; Eberly Distinguished Professor of Physics and Astronomy Maura McLaughlin; Nate Garver-Daniels, System Administrator, Department of Physics and Astronomy; and post-docs and former students Harsha Blumer, Paul Brook, Pete Gentile, Megan Jones and Michael Lam.
The discovery is one of many fortuitous results, according to McLaughlin, that emerged during routine observations made as part of a gravitational wave search.
"At Green Bank, we are trying to detect the gravitational waves of pulsars," she said. "To do this, we need to observe a lot of millisecond pulsars, which are rapidly rotating neutron stars. This (the discovery) is not a gravitational wave detection paper, but one of the many important results from our observations. "
The mass of the pulsar was measured by a phenomenon called "Shapiro delay". In essence, the gravity produced by a white dwarf companion star deforms the space around it, according to Einstein's theory of general relativity. This causes pulsar pulses to move a little farther as they move in deformed space-time around the white dwarf. This delay tells them the mass of the white dwarf, which provides a mass measurement of the neutron star.
Neutron stars are the compressed remains of massive stars that have disappeared into supernovae. They are created when giant stars die in supernovas and their nuclei collapse, protons and electrons merging into each other to form neutrons.
To visualize the mass of the neutron star discovery, a single piece of neutron star material sugar would weigh 100 million tons on Earth, roughly the same as the entire the human population.
While astronomers and physicists have been studying these objects for decades, many mysteries remain about the nature of their interiors: Do the crushed neutrons become "superfluid" and flow freely? Do they break down into a soup of subatomic quarks or other exotic particles? What is the tipping point when gravity overrides matter and forms a black hole?
"These stars are very exotic," said McLaughlin. "We do not know what they are made of and a very important question is:" What mass can you create for any of these stars? "This has implications for very exotic material that we simply can not create in a laboratory on Earth."
Pulsars bear their name because of the double beam of radio waves that they emit from their magnetic poles. These beams sweep the space like a lighthouse. Some rotate hundreds of times every second.
Pulsars rotating with phenomenal speed and regularity, astronomers can use them as the cosmic equivalent of atomic clocks. This accurate timestamp helps astronomers study the nature of space-time, measure the masses of stellar objects and better understand general relativity.
-WVU / NRAO-
js / bs / 09/16/19
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