HILO — The W. M. Keck Observatory atop Mauna Kea is at the forefront of an effort to learn whether there’s a fifth and as-yet-unproven force in the universe that makes gravity work.
“Over the last two decades, we’ve been working on this. It’s one of the key projects of the observatory,” said Randy Campbell, Keck science operations manager.
According to an abstract in Physical Review Letters, scientists at the University of California, using data from Keck, have shown that “stars orbiting around the supermassive black hole in our galactic center can successfully be used to probe the gravitational theory.”
The goal is to see if a particular star at the center of the Milky Way wavers from its predicted path when it gets super close to the black hole.
If the star’s path does waver, it will be evidence that a “fifth force of nature” exists. Previously, scientists found there were only four forces of nature: gravity, electromagnetism, strong nuclear forces and weak nuclear forces.
Scientists have long grappled with Einstein’s theory of relativity.
“Some of the theories of gravity are not fully understood at this point,” Campbell said.
But according to the UC research, “there are hints of a fifth force of nature, and if it exists, we’d not only be able to fill the remaining holes in Einstein’s general relativity, we’d have to rethink our understanding of how the universe actually works.”
Researcher Andrea Ghez, director of University of California, Los Angeles Galactic Centre Group, has been working closely with Keck.
She believes the best place to look for confirmation of a fifth force of nature “would be somewhere in the universe where the influence of gravity is so strong (that) signs of something extra will be easier to detect.”
“One of these stars is going to go very close to the black hole next year,” Campbell said. “We’re gearing up for this.”
Images must be captured at precise intervals — known in observatory language as “cadence” — to show what Ghez needs to see.
That’s why the observatory is making preparations to study the approach of the planet SO-2 to the black hole.
When the planet nears the black hole, its orbit is expected to change rapidly.
“Its orbit is going to be altered by general relativity — and perhaps this fifth force,” Campbell said.
The observatory faces challenges to capture the needed images. Infrared-sensitive instruments are used to search for infrared light, which is able to travel through the dust of space.
Earth’s atmosphere is “turbulent,” Campbell said. It’s like paddle-boarding, he said.
“If it’s a perfectly calm day, the water’s like glass, you can see the bottom. You can see the coral. You can see the fish really well,” he said. But, if the water’s choppy, it’s hard to see any of that.
Similarly, Earth’s atmosphere requires the use of “adaptive optics” that use a mirror that “flattens out the wave front and gives us the sharpest images possible,” Campbell said.
He said Mauna Kea is the best place to collect the data because it “has the most nights that are clear and stable of anyplace on Earth. If we were trying to do this, even from Maui, it wouldn’t be as good.”
When planet SO-2 nears the black hole next year, the university declared, “if there are any deviations from what general relativity predicts, this will be the best time to spot them.”
Email Jeff Hansel at jhansel@hawaiitribune-herald.com.