Space & time

Chilean telescope finds record-breaking neutron star

The massive object is orbited by a dwarf star, providing perfect conditions to test Einstein’s general relativity theory - and so far it holds up.

Monday, May 20, 2013  
Artist’s impression of the pulsar PSR J0348+0432 and its white dwarf companion. Photo by ESO. Artist’s impression of the pulsar PSR J0348+0432 and its white dwarf companion. Photo by ESO.


The European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile’s Atacama has contributed to the study of an extraordinary binary system that has allowed astronomers to conduct tests that were previously impossible.

Discovered by radio telescopes, the new pulsar, or neutron star, named PSR J0348+0432 is the largest of its kind ever discovered. The pulsar, the remains of a supernova, is twice the mass of the sun, despite only measuring 20 kilometers across!

Gravity at the pulsar’s surface is 300 billion times stronger than that on earth; a sugar cube sized part of its center has more than 100 billion tons of matter squeezed into it.

Though the discovery of this pulsar is impressive enough, what excites astronomers most is the white dwarf star that orbits it every two-and-a-half hours.

“I was observing the system with ESO’s Very Large Telescope, looking for changes in the light emitted from the white dwarf caused by its motion around the pulsar,” John Antoniadis, of the Max Planck Institute for Radio Astronomy (MPIfR) and lead author of the paper, said. “A quick on-the-spot analysis made me realize that the pulsar was quite a heavyweight. It is twice the mass of the Sun, making it the most massive neutron star that we know of and also an excellent laboratory for fundamental physics.”

By studying the behavior of the white dwarf in orbit, scientists can test Albert Einstein’s theory of general relativity, which explains gravity as a consequence of the curvature of spacetime created by the presence of mass and energy.

Einstein’s theory has stood up to tests for almost 100 years, though ultimately it is predicted to fall as it is not consistent with the theory of quantum mechanics.

Studies of this binary system have held up Einstein’s theory and were inconsistent with competing theories. Such a binary radiates gravitational waves and loses energy. This causes the orbital period to change very slightly and the predictions for this change from general relativity and other competing theories are different.

“Our radio observations were so precise that we have already been able to measure a change in the orbital period of 8 millionths of a second per year, exactly what Einstein’s theory predicts,” Paulo Freire, another member of the study, said.

Studies of this new astronomical phenomenon have just begun, and tests of greater accuracy will be carried out shortly.

Due to its almost non-existent humidity and clear skies, the Atacama is the world’s premier location for astronomy. Chile is home to almost half the world’s telescope infrastructure, and this is set to increase to over two thirds in the next decade.