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Astronomers use a Pulsar to Measure Space-Time Warp for the First Time

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Astronomers use a Pulsar to Measure Space-Time Warp for the First Time

A pair of stars orbiting each other has allowed astrophysicists to measure the space-time warp caused by the high gravity produced by the proximity of very heavy stars. Astronomer Ingrid Stairs and Joeri van Leeuwen, an astrophysicist at the Netherlands Institute for Radio Astronomy, and University of Amsterdam, are the first to see the disappearance of a neutron star due to gravitationally induced changes in space and time.

The researchers measured the masses of two stars in a binary pulsar system, called J1906. This pulsar spins and emits a lighthouse-like beam of radio waves every 144 milliseconds. In addition, it orbits its companion star in a little under four hours.

Neutron stars wobble like a spinning top as they move through the gravitational well of a massive, nearby companion star. Orbit after orbit, the pulsar travels through a space-time that is curved, which impacts the star’s spin axis.


“By precisely tracking the motion of the pulsar, we were able to measure the gravitational interaction between the two highly compact stars with extreme precision,” said Ingrid Stairs. “These two stars each weigh more than the sun, but are still over 100 times closer together than Earth is to the sun. The resulting extreme gravity causes many remarkable effects.”

One of these is geodetic precession of the spin axis of the pulsar. When you start a spinning top, it doesn’t only rotate — it also wobbles. According to general relativity, neutron stars, too, should start to wobble as they move through the gravitational well (the highly curved space-time) of a massive, nearby companion star.

The team kept track of the geodetic precession in J1906 and noticed a change of 2.2 degrees in the orientation of the pulsar spin axis.

Through the effects of the immense mutual gravitational pull, the spin axis of the pulsar has now wobbled so much that the beams no longer hit Earth.

The pulsar is now all but invisible to even the largest telescopes on Earth. This is the first time such a young pulsar has disappeared through precession. Fortunately this cosmic spinning top is expected to wobble back into view .. but it might take as long as 160 years.

The mass of only a handful of double neutron stars have ever been measured, with J1906 being the youngest. It is located about 25,000 light years from Earth.


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