Do we understand gravity? The GBT says yes!

Einstein’s theory of relativity passes a range of precise tests set by pair of extreme stars

Artistic impression of the Double Pulsar system, where two active pulsars orbit each other in just 147 minutes. The orbital motion of these extremely dense neutron stars causes a number of relativistic effects, including the creation of ripples in spacetime known as gravitational waves. The gravitational waves carry away energy from the systems which shrinks by about 7mm per day as a result. The corresponding measurement agrees with the prediction of general relativity within 0.013%. © Michael Kramer/MPIfR

The National Science Foundation’s Green Bank Telescope (GBT) was one of seven radio telescopes around the world whose combined observations of a Double Pulsar reinforce Albert Einstein’s theory of general relativity.

More than 100 years after Einstein proposed it, scientists around the world continue their efforts to find flaws in his theory of general relativity, which expresses gravity in relation to space and time. The observation of any deviation from general relativity would constitute a major discovery that would open a window on new physics beyond our current theoretical understanding of the Universe.

The research team’s leader, Professor Michael Kramer from the Max Planck Institute for Radio Astronomy in Bonn, Germany, shares, “We studied a system of compact stars that is an unrivalled laboratory to test gravity theories in the presence of very strong gravitational fields. To our delight we were able to test a cornerstone of Einstein’s theory, the energy carried by gravitational waves, with a precision that is 25 times better than with the Nobel-Prize winning Hulse-Taylor pulsar, and 1000 times better than currently possible with gravitational wave detectors.” He explains that the observations are not only in agreement with the theory, “but we were also able to see effects that could not be studied before”.

Read the release from the Max Planck Institute for Radio Astronomy.

The GBT has provided monthly observations of this Double Pulsar system for roughly 14 years. With its 100-meter diameter and state-of-the-art receivers, the GBT is the cornerstone of the observational campaign, as it provides more sensitive timing observations than any other telescope.

The seven radio telescopes used for observations of the Double Pulsar PSR J0737-3039. Clockwise from upper left: Effelsberg Radio Telescope (Germany), Nançay Radio Telescope (NRT, France), Westerbork Synthesis Radio Telescope (WSRT, The Netherlands), Parkes Radio Telescope (Australia), Jodrell Bank Telescope (UK), Very Long Baseline Array (VLBA, U.S.), Green Bank Telescope (GBT, U.S.). The picture at higher resolution is accessible in the left column. © Norbert Junkes/MPIfR (Effelsberg), Letourneur and Nançay Observatory (NRT), ASTRON (WSRT), ATNF/CSIRO (Parkes), Anthony Holloway (Jodrell Bank), NRAO/AUI/NSF (VLBA), NSF/AUI/Green Bank Observatory (GBT).

The international team consists of scientists from ten countries, including West Virginia University Professors Maura McLaughlin and Duncan Lorimer, who use the GBT for many of their research projects. Both McLaughlin and Lorimer were part of the team that discovered this Double Pulsar system in 2003. Watch a video explaining the dynamics of this Double Pulsar. This video was created by Josh White, Maura McLaughlin, and Nihan Pol for the Center for Gravitational Waves and Cosmology It was funded by National Science Foundation award number 1517003.

“The observations of this Double Pulsar system allowed astronomers to test and confirm seven different predictions of Einstein’s theory of relativity. The Double Pulsars reveal subtle interactions between the internal structure of one of the pulsars and the system as a whole. Since we still don’t know much about the interior of a neutron star, this is a really interesting result. The team is also measuring small changes in the way that light moves through curved space and time that can’t be seen anywhere else,” shares Ryan Lynch, a Green Bank Observatory scientist whose research focuses on pulsars. He continues, “As the recent 2020 Decadal Survey on Astronomy and Astrophysics shows, astronomers and physicists place a really high priority on uncovering and understanding new physics. The GBT’s capabilities are constantly evolving to be a fundamental part of this exciting work.”

These results, published in the Physical Review X, come from a 16-year long experiment to challenge Einstein’s theory of general relativity with some of the most rigorous tests to date. This study of a pair of extreme stars revealed new relativistic effects that were expected–but have only now been observed for the first time.

To learn more about Green Bank Observatory science and to see research opportunities visit our website.

Join staff from the Green Bank Science Center as they lead you in making – and observing – your own pulsar at home! Download the free Physics Toolbox Suite app to track your pulsar using your mobile device. Watch the video now. Find instructions to go along with this video here.

The Green Bank Observatory is a facility of the National Science Foundation and is operated by Associated Universities, Inc.



Jill Malusky, Green Bank Observatory Public Relations, ude.o1709519200arn@y1709519200ksula1709519200mj1709519200