The Hubble Space Telescope captured the gravitational lens of the galaxy LRG 3-757.
(ESA/Hubble and NASA)
A new study confirms Einstein’s general theory of relativity in a distant galaxy for the first time.
This research supports our current understanding of gravity and provides more evidence for the existence of dark matter and dark energy — two mysterious concepts that scientists know only indirectly, by observing their effects on the cosmic objects.
Albert Einstein’s general theory of relativity, published in 1916, explains how gravity is the result of a concept known as the structure of space-time. Simply put, the theory predicts how much the mass of an object, in this case, a galaxy — curves of the space-time. [Einstein’s theory of Relativity Explained (Infographic)]
Since the theory was published for the first time, is tested on a number of times in our solar system. But this new research, carried out by an international team of astronomers under the leadership of Thomas Collett of the Institute of Cosmology and Gravitation at the University of Portsmouth in the united kingdom, is the first accurate test of the general theory of relativity on a large astronomical scale, the researchers said.
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Using data from NASA’s Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope in Chile, the research team discovered that the force of gravity behaves in the same way in a far away galaxy and in our solar system, just as Einstein’s theory predicts.
The researchers tested the hypothesis that “the laws of physics we see here on Earth are everywhere else,” Terry Oswalt, an astronomer and chairman of physical sciences at Embry-Riddle Aeronautical University in Florida, said in an e-mail to Space.com. The verification of the general theory of relativity “on all possible scales (especially the largest scale) is of fundamental importance for the physics as a whole, and to cosmology in particular,” said Oswalt, who was not involved in the new study.
To validate the general theory of relativity, the findings also serve as additional evidence for the existence of dark matter and dark energy, told Collett Space.com. Dark matter and dark energy are two of the “weird things” that occur in the standard model of cosmology, Collett said.
The standard model is a theory that describes how the fundamental forces and particles in the universe work and act together, and want to explain our observations and experiments. However, our lack of understanding and of explanation of dark matter and dark energy, “the two greatest mysteries in cosmology today,” according to Oswalt, lead a number of questions to the standard model.
“I doubt astronomers give of the standard model of cosmology anytime soon,” Oswalt said. So, instead of leaving the standard model, researchers look to “the models more precisely explain the observed data,” he added.
In the standard model, dark matter is needed to explain how fast stars orbit around galaxies, and dark energy is needed to explain why the universe is expanding faster, according to Collett.
Some scientists have suggested that “alternative gravity theories,” as Collett described, could be that there is a necessity for dark matter and dark energy in the standard model. However, because this team has found that the gravity functions outside of our solar system, just as in our solar system, now it turns out that our understanding of gravity is correct and dark matter and dark energy still fit in the standard model.
Collett noted that this study is not concrete “proof” of dark matter and dark energy, but it serves as additional evidence that they exist.
To validate the general theory of relativity outside of our solar system for the first time, the research team used strong gravitational lensing, a technique in which a solid object, in this case, a galaxy acts as a lens by bending the light so much that the image of a background object, a galaxy is distorted. This team of astronomers used the galaxy ESO 325-G004 as it is one of the best lenses to the Earth, only about 500 million light-years away.
If the two objects are aligned, this effect creates a ring of images, which is known as an “Einstein ring” of the background galaxy. The radius of the ring “is in proportion to the deflection of the light,” Collett said: “so if you measure the radius of the ring, you can measure the curvature [space-time].”
In addition to the measure of the space-time curve, the researchers had to determine the galaxy’s mass, because the general theory of relativity predicts how much curvature is created by a mass. They calculated this mass by measuring how fast the galaxy s the stars travel. Then, by comparing the measured mass with the measured curvature of space-time, the team is what general relativity predicts for these masses, or galaxy.
So now, as far as we know, even outside of our solar system, general relativity is the correct theory of gravity, Collett said. This team of astronomers hopes to study further galaxies, or lenses, to verify that gravity works also in the rest of the cosmos.
“It is so satisfying to the best telescopes in the world to the challenge of Einstein, only to find out how right he was,” team member Bob Nichol, director of the Institute of Cosmology and Gravitation, said in a statement.
The work is published today (21 June) in the journal Science.
Original article on Space.com.