Science

Star That Orbits Black Hole Supports Einstein’s Theory

Star That Orbits Black Hole
Image source: YouTube Video Screenshot

Scientists have observed a behavior deep in space that confirms a theory over 100 years old. A group of researchers observed a star that orbits a black hole, finding it supports Einstein’s theory of general relativity which indicates that gravity affects the curvature of space and time. However, scientists believe this evidence may not last forever.

Einstein’s theory of general relativity was tested by Andrea Ghez, professor of physics and astronomy at the University of California Los Angeles, measuring the gravity interaction between a star and the black hole at the heart of the Milky Way. The results of the study were published in the journal Science.

“Einstein’s right, at least for now,” Ghez, a co-lead author of the study, said in a statement. “We can absolutely rule out Newton’s law of gravity. Our observations are consistent with Einstein’s theory of general relativity. However, his theory is definitely showing vulnerability. It cannot fully explain gravity inside a black hole, and at some point we will need to move beyond Einstein’s theory to a more comprehensive theory of gravity that explains what a black hole is.”

According to Ghez, Einstein’s theory, at the moment, is the best explanation of how gravity works, as observing the star that orbits the black hole appears to confirm. They observed several instances in which the star made a close approach to the black hole. It approached the closest in April, May and September of 2018, moving 16 million miles per hour. Using spectral data that determines wavelengths of light showed scientists what the star is made of. They also combined measurements the team collected over the past 24 years.

The team collected data from a spectrograph at the university, as well at the W.M. Keck Observatory in Hawaii. The combination of data helped the scientists make accurate measurements of the star’s movement. The researchers noticed a space time warp as the star approached the black hole.

“In Newton’s version of gravity, space and time are separate, and do not co-mingle; under Einstein, they get completely co-mingled near a black hole,” she said.

The star was at a far enough distance away from the black hole which allowed it not to get pulled into it. The particles of light known as photons that scientists tracked to see the star, had traveled over 26,000 years. It took years for Ghez and her team to prepare to make measurements of the photons to prove Einstein’s theory.

“For us, it’s visceral, it’s now — but it actually happened 26,000 years ago,” she said.

Ghez observed more than 3,000 stars that orbit the black hole in the center of the Milky Way, so the next steps in this study include observing more stars that orbit near the black hole, including S0-102 which has a short orbit lasting only 11 and a half years.

“We’re learning how gravity works. It’s one of four fundamental forces and the one we have tested the least,” she said. “There are many regions where we just haven’t asked, how does gravity work here? It’s easy to be overconfident and there are many ways to misinterpret the data, many ways that small errors can accumulate into significant mistakes, which is why we did not rush our analysis.”