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Arecibo Observatory Helps Test Einstein’s Theory of Relativity for Heavy Objects

The Arecibo Observatory helped scientists demonstrate that Einstein’s theory of relativity applies even to objects with extreme gravity, such as neutron stars.

By Zenaida Gonzalez Kotala |
July 5, 2018

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An international team of researchers today published findings from its six-year study in Nature.

“The high-quality data we have from Arecibo allowed us to divide the data up into subsections and compare them with each other, allowing us to resolve an apparent conflict with Einstein’s gravity.”

“Thanks to the power of Arecibo and in conjunction with the Westerbork Synthesis Radio Telescope here in the Netherlands and the Green Bank Telescope in West Virginia we were able to show that Einstein’s theory of relativity holds water even when it comes to neutron stars and dwarf stars,” said lead scientist Anne Archibald, a postdoctoral researcher of the University of Amsterdam and ASTRON at the Netherlands Institute for Radio Astronomy.

A UCF-led team manages the Arecibo Observatory in Puerto Rico, home to one of the most powerful radio-radar telescopes in the world.

A key part of Einstein’s theory is that objects, regardless of their composition or mass, fall the same way. Just think of dropping a feather and a bowling ball from the same point. They both hit the ground at the same time. But some theories predict that when it comes to objects with extreme gravity, they will in fact fall differently. Archibald’s research indicates otherwise.

Archibald and her team observed a system of stars that had just the right extreme combination — the triple star system called PSR J0337+1715, located 4,200 light years from the Earth.

In this unique system, a neutron star is in a 1.6-day orbit with a white dwarf, and this pair is in a 327-day orbit with another white dwarf farther away. If alternative theories of gravity were correct, then the neutron star and the inner white dwarf would fall differently towards the outer white dwarf.

“We were able to measure this by looking at the neutron star alone,” Archibald said. “The neutron star, a millisecond pulsar, behaves like a clock: it rotates 366 times per second, and beams of radio waves rotate along. They sweep over the earth at regular intervals, like a cosmic lighthouse. We have used these radio pulses to track the position of the neutron star.”

Arecibo played a central role, providing data that the team analyzed to reach its conclusion that Einstein’s theory holds, Archibald said.

“The high-quality data we have from Arecibo allowed us to divide the data up into subsections and compare them with each other, allowing us to resolve an apparent conflict with Einstein’s gravity.”

This powerful test of gravity is possible because PSR J0337+1715 is a natural laboratory. But there may be more remarkable millisecond pulsar systems waiting to be discovered, said co-author Jason Hessels, an associate professor at ASTRON and the University of Amsterdam.

“Among these yet undiscovered systems may lurk even more powerful tools for understanding the universe: unusual binaries, other triple star systems or a pulsar orbiting a black hole. Perhaps one of these may provide our first peek at a theory beyond Einstein’s,” Hessels said.

For now, Einstein’s theory stands. For more information about the study, check out today’s Nature online publication.