Einstein's insights into gravity still hold sway, theory passes extreme test

Mindy Sparks
July 8, 2018

Massive objects, such as galaxies, warp space-time, according to Einstein's theory of general relativity. An worldwide team of astronomers has given this lingering question its most stringent test ever.

A group of astronomers at the The University of British Columbia (UBC) have proved that Einstein's theory of general relativity holds up, even for a massive three-star system.

Take away all air, and a hammer and a feather will fall at the same rate - a concept explored by Galileo in the late 1500s and famously illustrated on the Moon by Apollo 15 astronaut David Scott. Alternative theories to General Relativity are not looking too good at this time.

As a neutron star - an object of very small radius (typically 30 km) and high density - carries extremely strong self-gravitation and makes the right candidate for the test equivalence principle, the global research team looked at a unique three-star system consisting a neutron star and two white dwarfs - stellar bodies that are just as big as Earth but carry the sun's mass. That difference would be due to a compact object's so-called gravitational binding energy - the gravitational energy that holds it together.

"This particular system consists of one ultra-dense neutron star and two less-dense white dwarf stars, which makes these stars the dream team for testing relativity", Dr Deller says. The star system has is a neutron star locked in a rapid orbit that lasts only 1.6 days around a white dwarf star, the two bodies are, in turn, on a 327-day orbit around another white dwarf star much further away.

This triple star system provides a great test bed for the theory of relativity. - We know of no other such systems. "That makes it a one-of-a-kind laboratory for putting Einstein's theories to the test", Ryan Lynch of the Green Bank Observatory in the USA said.

To test the theory of general relativity on something much larger, teams from the Arecibo Observatory in Puerto Rico, the Green Bank Observatory in the United States and the Dwingeloo Radio Observatory in the Netherlands looked at a triple star system discovered in 2012.

How were these telescopes able to study this system? Strong samoogranichitsja neutron star.

Earlier this year, with the help of the atomic clocks we use to keep time, a team of scientists showed Earth is falling through space at a steady rate, unaffected by the pulls of the Sun, Jupiter, and other cosmic objects, as Einstein thought. "As one of the most sensitive radio telescopes in the world, the GBT is primed to pick up these faint pulses of radio waves to study extreme physics", Lynch said.

The work is so precise that scientists can account for every single pulse of the neutron star since the beginning of their observations, and they can tell its location to within a few hundred meters. "That is really a precise track of where the neutron star has been and where it is going".

In this case you could think of the neutron star as the hammer and the inner white dwarf as the feather - it shows high-mass bodies "fall" at the same rate as low-mass bodies, which again is a core component of the equivalence principle. The "inner white dwarf" and the pulsar are extremely distinct objects.

Because they do not have a gravitational force as strong as neutron stars, the researchers found it intriguing to find two white dwarfs in the same vicinity as a neutron star. The researchers say the difference is not more than three parts in 1 million. A whole range of these competing theories have been severely constrained by the findings of this test.

Researcher have found the ideal "laboratory" to test one of the principles of Einstein's theory of relativity and proved him right one more time.

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