Ripples in spacetime prove Einstein right again

artist’s impression shows the exotic double object that consists of a tiny, but very heavy neutron star that spins 25 times each second, orbited every two and a half hours by a white dwarf star. The neutron star is a pulsar named PSR J0348+0432 that is giving off radio waves that can be picked up on Earth by radio telescopes. Credit: ESO / L. Calcada

Score another point for Einstein. Astronomers studying a bizarre star system have found that relativity theory’s prediction snugly matches observation.

One of my favorite spectator sports is watching scientists put a new theory to the test. No blood lust on my part, but I like the way science works. The more amazing the hypothesis, the more scrutiny it receives. That’s as it should be. If someone told you that eating banana peels cures cancer and heart disease, you’d want to see proof, backup studies and all the rest before you took your first chew.

Einstein’s General Relativity Theory must be the winner for the most studied and hen-pecked scientific paradigm. Weird notions like warped space and time, mass equals energy and the speed of light as the absolute universal speed limit test the limits of credulity. Can all this really be true? Heck yeah.

Since 1916, when it was first published, scientists have thrown every test they can think of at Relativity – it’s always come up shining. Along with quantum mechanics, Einstein’s ideas have become a pillar of modern physics.

A pulsar is a tiny, rapidly-spinning neutron star left after a supernova explosion that beams radiation (purple) into space from its magnetic poles. From Earth we see the beams as a series of rapid pulses of light. Credit: NASA

Recently, astronomers using the European Southern Observatory’s Very Large Telescope (VLT) in conjunction with radio telescopes around the world, fired off another truth bomb at the theory in an exotic environment impossible to duplicate on Earth. Their target was an odd couple –  a city-sized, pulsating neutron star called a pulsar orbited every 2 1/2 hours by an Earth-sized white dwarf star.

A neutron star forms in the aftermath of some supernova explosions during the gravitational collapse of a supergiant star many times larger than the sun. The collapse causes both a shock wave that rips the star apart and crushing pressure on the core, which gets squeezed into a tiny ball of neutrons (subatomic particles).White dwarfs are the end stage of life for stars like the sun; not quite as compact as pulsars, a teaspoonful still weighs 5.5 tons.

Another view of the pulsar PSR J0348+0432 and its white dwarf companion. The system radiates gravitational radiation shown here as blue waves. Although these waves can’t be be detected directly, they can be detected indirectly by measuring the change in the orbit of the system as it loses energy. Credit: ESO / L. Calcada

With virtually no empty space left between the particles, neutron stars are unimaginably dense. Gravity at the surface of PSR J0348+0432 is 300 billion times stronger than that on Earth; a sugar cube’s worth of material from its core would weigh 1 billion tons. All neutron stars are extremely compact, but this one’s the heaviest known and only 12 miles (20 km) across.

The team combined Very Large Telescope observations of the white dwarf with very precise timing of the pulsar from radio telescopes. According to Einstein, a close stellar pair with powerful gravitational fields like these two radiate gravitational waves – ripples in the fabric of spacetime – and lose energy. This causes the orbital period to change very slightly. Relativity makes a specific prediction on how much energy is lost as do other  alternative theories of gravity like the Modified Newtonian Dynamics (MOND) model.

Albert Einstein in 1947 (left) and in 1904 when he worked in a Swiss patent office. Click photo to read more about the pulsar study. Credit: Lucian Chavan (l) and Oren Jack Turner

“Our radio observations were so precise that we have already been able to measure a change in the orbital period of 8 millionths of a second per year, exactly what Einstein’s theory predicts,” states Paulo Freire, a member of the team who did the study.

Once again, the man with the crazy hair takes home the prize.

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