Albert Einstein’s idea of gravitational microlensing was first proven in 1919, when astronomers noticed background stars were displaced by the eclipsed sun.
Now, nearly 100 years later, Einstein’s general theory of relativity has been confirmed again.
An international research team led by Kailash C. Sahu this week published what is believed to be the first report of a particular type of “gravitational microlensing” by a star outside the solar system.
In the early 20th century, Einstein predicted that if two stars aligned exactly, the background star would be distorted by the gravity of the foreground star, creating a so-called “Einstein ring” of light.
But what Sahu & Co. found was an asymmetrical version of an Einstein ring: The distant star appeared off-center from its true position.
“This part of Einstein’s prediction is called ‘astrometric lensing,’ and Sahu’s team was the first to observe it in a star other than the Sun,” according to Terry Oswalt of Embry-Riddle Aeronautical University.
Sahu, an astronomer at the Space Telescope Science Institute in Maryland, used the Hubble Space Telescope on eight dates between October 2013 and ’15 to measure shifts in a distant star as its light was deflected around nearby white dwarf star Stein 2051 B—the sixth-closest white dwarf to the Sun.
To a layperson, the news sounds like gibberish. But among astronomers, these findings are hugely significant.
The research “solves a long-standing mystery about the mass and composition of Stein 2051 B,” Oswalt said, adding that “we now know [it] is perfectly normal.”
Perhaps more importantly, this new tool “will be very valuable,” according to Oswalt, an astronomer and chair of the Department of Physical Sciences at Embry-Riddle’s Daytona Beach campus.
Over the next decade, stargazers like Sahu and Oswalt will continue high-definition monitoring, keeping their fingers crossed for more chance alignments.
“Einstein would be proud,” Oswalt said. “One of his key predictions has passed a very rigorous observational test.”
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