An international team has used telescopes around the world to complete the most challenging tests yet to demonstrate the validity of Einstein’s theory of relativity.
The observation of any deviation from general relativity, enunciated more than 100 years ago, would constitute an important discovery that is beyond our current theoretical understanding of the Universe.
Research team leader Michael Kramer of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, says in a statement: “We study a compact star system that is an unrivaled laboratory for testing theories of gravity in the presence of very strong gravitational fields. To our delight, we were able to test a cornerstone of Einstein’s theory, , with an accuracy that is 25 times better than with the Nobel Prize winning Hulse-Taylor pulsar, and 1,000 times better than what is currently possible with gravitational wave detectors. ”
The scientist explains that the observations not only agree with the theory, “But we were also able to see effects that could not be studied before.”
Ingrid Stairs of the University of British Columbia in Vancouver gives an example: “We follow the propagation of radio photons emitted by a cosmic beacon, a pulsar, and trace their movement in the
“We see for the first time how the light is not only delayed due to a strong curvature of space-time around the companion, but also thats that we can detect. Never before had an experiment of this type been carried out with such a high space-time curvature ”.
This cosmic laboratory known as the “Double Pulsar” was discovered by team members in 2003. It consists of two radio pulsars that orbit each other in just 147 minutes with speeds of approximately 1 million km / h. A pulsar spins very fast, about 44 times per second. The partner is young and has a rotation period of 2.8 seconds. It is their movement around the other that can be used as
Dick Manchester of Australia’s national science agency CSIRO illustrates: “Such fast orbital motion of compact objects like these, about 30% more massive than the Sun but only about 15 miles wide, allows us to test many different predictions of general relativity – seven in all! In addition to gravitational waves, our precision allows us to probe the effects of light propagation, such as the so-called ‘Shapiro delay’ and bending of light. We also measure the effect of ‘time dilation’ that makes
“We must even take into account Einstein’s famous equation E = mc2 when considering the effect of electromagnetic radiation emitted by the fast-spinning pulsar on orbital motion. This radiation corresponds to a loss of mass of 8 million tons per second! While this sounds like a lot, it is only a tiny fraction – 3 parts in a billion trillion trillion! – of the pulsar’s mass per second ”.
The researchers also measured, with an accuracy of 1 part in a million, that, a relativistic effect also known from the orbit of Mercury, but here 140,000 times stronger. They found that at this level of precision they must also consider the impact of the pulsar’s rotation on the surrounding spacetime, which is “pulled” with the rotating pulsar.
Norbert Wex of the MPIfR, another lead author of the study, explains: Physicists call this the Lense-Thirring or frame-dragging effect. In our experiment, it means that we must consider the internal structure of a pulsar like a neutron star. Therefore, our measurements allow us for the first time to use precision tracking of neutron star rotations, to provide constraints on the extent of a neutron star ”.
The pulsar synchronization technique was combined with careful interferometric measurements of the system to determine its distance with high-resolution images, resulting in a value of 2,400 light-years with only an 8% margin of error.
Team member Adam fDeller, from the University of Swinburne in Australia and responsible for this part of the experiment, highlights: “It is the combination of different complementary observational techniques that adds to the extreme value of the experiment. In the past, similar studies have often been hampered by limited knowledge of the distance of such systems. This is not the case here, where in addition to pulsar timing and interferometry t obtained from the effects due to the interstellar medium “.
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