A consortium of astronomers said Thursday they had for the first time confirmed a prediction of Albert Einstein’s theory of general relativity by observing the gravitational effects of a supermassive black hole on a star zipping by it.
The German-born theoretical physicist had posited that large gravitational forces could stretch light, much like the compression and stretching of sound waves we perceive with the change of pitch of a passing train.
Researchers from the GRAVITY consortium led by the Max Planck Institute for Extraterrestrial Physics realised that they had a “perfect laboratory” to test Einstein’s theory with the Sagittarius A* black hole in the centre of the Milky Way.
Black holes are so dense that their gravitational pull can trap even light, and the supermassive Sagittarius A* has mass four million times that of our sun, making it the biggest in our galaxy.
Astronomers followed the S2 star as it passed close to the black hole on May 19 at a speed in excess of 25 million kilometres (15.5 million miles) per hour.
They then calculated its velocity and position using a number of instruments and compared it with predictions made by Einstein that the light would be stretched by the gravity in an effect called gravitational redshift. Newtonian physics doesn’t allow for a redshift.
“The results are perfectly in line with the theory of general relativity” and are “a major breakthrough towards better understanding the effects of intense gravitational fields,” said the research team, whose findings are published in Friday’s issue of Astronomy & Astrophysics.
This is the first time observers have been able to measure such an effect.
The European Southern Observatory, whose Very Large Telescope in Chile was used to make the observations, had watched S2 pass by Sagittarius A* in 2016 but the instruments it was using then were not sensitive enough to detect the gravitational redshift.
“More than 100 years after he published his paper setting out the equations of general relativity, Einstein has been proved right once more — in a much more extreme laboratory than he could have possibly imagined,” said the ESO in a statement.
Astronomers already use another effect predicted by Einstein’s theory of general relativity — that a black hole can bend passing light. Called gravitational lensing, researchers have used it to peer behind black holes.
Astronomers hope they can make practical use of the latest confirmation of Einstein’s theory to track shifts in S2’s trajectory due to gravity, which could yield information on mass distribution around the black hole.
“I am always blown away by Einstein’s predictions, by the power of his reasoning which yielded this theory and which has never been faulted,” French astrophysicist Guy Perrin, a member of the GRAVITY consortium, told AFP.
Partnering with the Max Planck Institute in the consortium were French research institute CNRS, the Paris Observatory and several French universities along with Portugal’s CENTRA astrophysics centre.
‘This American dream’: Pain overwhelms family of drowned migrants
"They had this American dream," sobbed Rosa Ramirez after images of her drowned son and granddaughter, discovered face-down on the banks of the Rio Grande between Mexico and the United States, shocked the world on Wednesday.
The poignant pictures of Oscar Alberto Martinez and his toddler daughter Valeria -- not yet two years old -- has sparked outrage back home in El Salvador, where around 200 migrants like them leave for the United States daily, preparing to take similar risks.
"The pain has been immense. I still can't believe that my boy and my little granddaughter are dead, they only wanted to get to the United States.... they had this American dream -- to achieve a better life," Oscar's mother told AFP.
Venezuela government says thwarted attempted ‘coup’
Venezuela's socialist government said Wednesday it had derailed an attempted coup, claiming the United States, Colombia and Chile colluded in a military plot to assassinate President Nicolas Maduro and install a general and former defense minister in his place.
Communications Minister Jorge Rodriguez said the plan involved active and retired army officers and was to have been executed between Sunday and Monday this past weekend.
"We were in all the meetings to plan the coup d'Etat. We were in all the conferences," Rodriguez said, suggesting that government informers had infiltrated the alleged plotters during planning meetings.
Democrats believe Mueller testimony could be tipping point for impeachment: CNN
On Wednesday, CNN congressional correspondent Manu Raju reported that some House Democrats view special counsel Robert Mueller's upcoming public testimony to the House Intelligence and Judiciary Committees in July as a potential tipping point that could sway both Democratic leaders and the American people in favor of opening an impeachment probe.
"Democrats who support opening up an impeachment inquiry believe this could bolster the calls to open up formal proceedings, perhaps shift public opinion, perhaps encourage the House Speaker Nancy Pelosi to move off of her opposition to opening up an impeachment probe because of what Bob Mueller will say," said Raju.