Huge Neutron Star Discovered!

Astronomers at Green Bank Telescope have discovered the most massive neutron star we’ve ever seen!

The pulsar within the Crab Nebula. Taken by NASA/CHANDRA

Neutron stars are incredibly dense stars that are at the end of their lives. If you omit black holes, these stars the most dense objects in the universe. They weigh in at 1.4 solar masses on average, and just under 1’000 of them will snugly line up the Great Wall of China! Some of these stars rotate, and release repeated bursts of radiation, usually radio waves. These neutron stars are called pulsars, and were first discovered by Jocelyn Bell Burnell using a 4 acre telescope!


J0740+6620 is a millisecond pulsar 2.17 times the mass of the sun, all squished into a 30km diameter sphere. Millisecond pulsars are incredibly accurate and reliable timers. The mass was determined by using relativistic Shapiro delay (measuring the delay of a radar signal from spacetime dilation), and should be very close to the real mass. Shapiro delay, or gravitational delay, is one of the most accurate methods of measurement we’ve ever used on stars.

Artist’s impression of a pulsar. NASA

Over 2’000 neutron stars have been detected since their discovery, and are as small as 1.1 solar masses. The average neutron star is about 1.4 solar masses, not very close to J0740+6620’s amazing 2.17!


The most exciting part about this star is that it is on the limit of how massive a neutron star can be before it becomes a black hole. It’s really that massive! Understanding how these limit-approaching neutron stars behave will give astronomers another perspective on neutron stars, and also help us refine the limits of their mass.

Tops to you GBT!

Image courtesy of NRAO/AUI

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