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Heaviest star in the universe is almost 'too massive to exist'

Victor Adomako

Sept. 17, 2019

Astronomers have discovered the heaviest star in the universe that, they say, is more than twice the mass of our sun.
Amazingly, the star is only 15 miles across. That makes the density and the weight of it so huge as to be almost unimaginable.
It’s about 700,000 times heavier than Earth and is what’s known as a ‘neutron’ star – basically the compressed remains of a supernova. It happens when a giant star collapses in on itself in a massive explosion.
Despite bearing such an impressive title of ‘heaviest’ star in the known universe, it has a pretty uninspiring official name: J0740+6620.
According to the US team studying it, J0740+6620 is ‘the most massive neutron star ever detected — almost too massive to exist.’
The measurement approaches the limits of how compact a single object can be without crushing itself into a black hole.
It was detected about 4,600 light years from Earth by the Green Bank Telescope in West Virginia. One light year is about six trillion miles.
‘This neutron star is twice as massive as our Sun,’ said Paul Demorest, from the National Radio Astronomy Observatory (NRAO), in Charlottesville, Virginia.
‘This is surprising and that much mass means that several theoretical models for the internal composition of neutron stars now are ruled out.
‘This mass measurement also has implications for our understanding of all matter at extremely high densities and many details of nuclear physics.’
The researchers used an effect of Einstein’s theory of relativity to calculate its mass thanks to an orbiting companion star.
As the white dwarf passes directly in front of the pulsar this causing a delay for the time the radio waves take to reach earth.
The delay – called the Shapiro Effect – is caused by gravity enabling the mass of both stars to be precisely measured.
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