Wednesday, 27 October 2010

Radio astronomers find the largest-ever pulsar

Major news from the National Radio Astronomy Observatory today as reports emerge that radio astronomers have discovered the most massive pulsar yet found. The giant neutron-star is almost twice the mass of the sun, and it's discovery will have strong and wide-ranging impacts across several fields of physics and astrophysics.

Pulsars are spinning neutron-stars. They are the radiophonic clocks of the universe, emitting a steady pulse of radio waves with each rotation, which can be detected here on Earth using radio telescopes like the Green Bank Telescope (GBT). This most recent addition to the pulsar family is known as J1614-2230, and is located about 3,000 light-years away in the direction of the constellation Scorpio. It is nearly 20% more massive than any previously measured star of its class, and is rotating at an incredible speed, completing 317 rotations every second.

Described, rather poetically, by the National Radio Astronomy Observatory as "the superdense corpses of massive stars that have exploded", neutron-stars have long been known to be ideal natural laboratories for studying the most dense and exotic states of matter known to physics. With all their mass packed into a sphere the size of a small city, their protons and electrons are crushed together into neutrons. A thimbleful of neutron-star material would weigh more than 500 million tons.

Discovering a neutron-star as large as J1614-2230 has come as a major surprise to astrophysicists. It's not just it's sheer size that's causing a flurry, it's the implications for our understanding of what pulsars are made of. Most existing computer models can not account for neutron-stars bigger than 1.5 times the mass of the sun without resorting to modelling the star using exotic particles. But initial measurements of J1614-2230 seem to indicate that this giant amongst neutron-stars is made up of just that - neutrons - rather than the exotic matter, such as hyperons, that many theories have predicted. Paul Demorest of the National Radio Astronomy Observatory believes their discovery "weakens the possibility that neutron stars are made from anything other than neutrons".


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