Weighing twice as much as the Sun, it is the most massive neutron star measured to date. Together with a short orbital period of only 2.5 hours, the system provides insight into binary stellar evolution and the emission of gravitational radiation.
An artist’s impression of the PSR J0348+0432 binary system. The pulsar (with radio beams) is extremely compact, leading to a strong distortion of space-time (illustrated by the green mesh). The white-dwarf companion is shown in light-blue.
Science / J. Antoniadis (MPIfR)
The energy loss through this radiation has already been detected in the radio observations of the pulsar, making it a laboratory for General Relativity in extreme conditions. The findings are in excellent agreement with Einstein's theory.
Imagine half a million Earths packed into a sphere 20 kilometers in diameter, spinning faster than an industrial kitchen blender. These extreme conditions, almost unimaginable by human standards, are met in a neutron star – a type of stellar remnant formed in the aftermath of a supernova explosion. Neutron stars often catch the attention of astronomers because they offer the opportunity to test physics under unique conditions. They were first discovered almost half a century ago as pulsars which emit radio pulses like a lighthouse. Pulsar research has been honored with two Nobel prizes, one for their discovery (1974) and one for the first indirect detection of gravitational waves (1993) – a consequence of Einstein’s theory of General Relativity.
With these masses at hand, one can calculate the amount of energy taken away from the system by gravitational waves, causing the orbital period to shrink. The team immediately realized that this change in the orbital period should be visible in the radio signals of the pulsar and turned its full attention to PSR J0348+0432, using the three largest single-dish radio telescopes on Earth (Fig. 2). “Our radio observations with the Effelsberg and Arecibo telescopes were so precise that by the end of 2012 we could already measure a change in the orbital period of 8 microseconds per year, exactly what Einstein’s theory predicts”, states Paulo Freire, scientist at MPIfR. “Such measurements are so important that the European Research Council has recently funded BEACON, a new state-of-the-art system for the Effelsberg radio telescope.”In terms of gravity, PSR J0348+0432 is a truly extreme object, even compared to other pulsars which have been used in high precision tests of Einstein’s general relativity. At its surface, for example, it has a gravitational strength that is more than 300 billion times stronger than that on Earth. In the center of that pulsar, more than one billion tons of matter is squeezed into a volume of a sugar cube. These numbers nearly double the ones found in other ‘pulsar gravity labs’. In the language of general relativity, astronomers were able for the first time to precisely investigate the motion of an object with such a strong space-time curvature (see Fig. 1). “The most exciting result for us was, that general relativity still holds true for such an extreme object”, says Norbert Wex, a theoretical astrophysicist in MPIfR’s fundamental physics research group. In fact, there are alternative theories that make different predictions, and therefore are now ruled out. In this sense, PSR J0348+0432 is taking our understanding of gravity even beyond the famous ‘Double Pulsar’, J0737-3039A/B, which was voted as one of the top ten scientific breakthroughs of 2004 by the ‘Science’ journal.
BEACON: The Effelsberg observations were part of "BEACON", a 1.9-million-Euro project funded by the European Research Council aimed to push tests of gravity theories into new territories. Paulo Freire/MPIfR is the principal investigator of BEACON. The project has funded a state-of-the-art instrument to be installed at Effelsberg in the coming months that will target the pulsar with the aim to substantially improve the accuracy of the published results.Original Publication:
Norbert Junkes | Max-Planck-Institut
Further reports about: > Astronomie > Astronomy > ESO’s Very Large Telescope > Earth's magnetic field > European Research Council > Large Hadron Collider > MPIfR > Max-Planck-Institut > Mobile phone > Pulsar > Radioastronomie > Relativity > Telescope > extreme conditions > fundamental physics > general relativity > gravitational waves > neutron star > radio telescope > white dwarf
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