Radio signals from space have long fascinated astronomers scouting the cosmos for signs of alien life. In 2007, scientists were excited by the discovery of so-called Fast Radio Bursts (FRBs) reaching Earth from an unknown source in the universe. Forty years before that, astronomers encountered radio emissions reaching Earth from distant pulsars – fast-spinning neutron stars smaller than the Sun. Researchers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, have now mapped out one of these radio signals and confirmed in the process Albert Einstein’s general theory of relativity.
The discovery was made after 14 years of observations of the dead star PSR J1906+0746.
The pulsar sits around 25,000 light-years or 146,965,630,000,000,000 miles from Earth.
As the pulsar spins around, jets of bright radio waves shoot out from the star’s magnetic poles and fly out into space.
If the pulsar’s poles face the Earth’s general direction, the radio waves can wash over our planet like the light of a lighthouse.
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But unlike the guiding beam from a lighthouse, pulsar jets are incredibly fast and incredibly accurate.
In this case, the pulsar PSR J1906+0746 has a spin of just 144 milliseconds.
The Max Planck Institute said in a statement: “Due to their stable rotation, a lighthouse effect produces pulsed signals that arrive on Earth with the accuracy of an atomic clock.
“The large mass, the compactness of the source, and the clock-like properties allow astronomers to use them as laboratories to test Einstein’s general theory of relativity.”
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Pulsars can contain up to 40 percent more mass than our Sun but the material is densely packed into a sphere just 12 miles (20km) across.
The spinning stars also boast the most powerful magnetic fields in the universe.
These magnetic fields emit the jets of radio waves from the north and south poles in opposing directions.
Gregory Desvignes of the Max Planck Institute said: “PSR J1906+0746 is a unique laboratory in which we can simultaneously constrain the radio pulsar emission physics and test Einstein’s general theory of relativity.”
Dr Desvignes, who led the study, observed the pulsar between 2005 and 2018 to chart its radio emissions.
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During this time, the astronomers found the radio beams from the pulsar’s north pole disappeared from sight in 2016.
The disappearance was caused by the presence of a second neutron star nearby, which is distorting the spacetime surrounding the binary stars.
The distortion of spacetime through gravity is a key principle proposed by Einstein more than 100 years ago.
Professor Andrew Lyne of The University of Manchester, who observed the pulsar, said: “The extreme gravitational environment of the two neutron stars causes spacetime to be distorted.
“This in turn causes the pulsar to precess, changing the angle we view the radio emission and thus allowing us to map out the emission.”
The researchers estimate the precession will also take a toll on the remaining southern radio beam.
By the year 2028, the radio signals will no longer be visible from Earth.
The pulsar study was published this month on September 6 in the journal Science.