UC Santa Barbara graduate student Anna Pancoast, Vardha Bennert, physics senior Bryan Scott and former physics major Kelsi Flatland in front of the Shane Telescope at Lick Observatory in San Jose.
Using telescopes as time machines — that’s how Cal Poly physics assistant professor Vardha Bennert describes her current research project, which attempts to find what comes first: galaxies or black holes.
Do galaxies form around black holes? Or are black holes born into existing galaxies?
Scientists have been trying to solve this riddle for years, as black holes are at the center of every galaxy they study.
“What we found was a relationship between the mass of the black hole and the mass of the galaxy,” Bennert said. “The more massive the black hole, the more massive the galaxy, and vice versa. But the problem is that this isn’t necessarily expected, because the black hole is tiny compared to the entire galaxy. How does it know to have a black hole in its center?”
In the Milky Way galaxy, scientists have calculated a black hole that is approximately three million times the mass of the sun.
“You might wonder how we know there’s a black hole if, per definition, it’s black — if no light can escape from it,” Bennert said. “Well, you can determine the mass of a black hole just by its gravitational influence on the objects around it.”
Bennert, along with physics senior Bryan Scott and junior Nathan Milgram, will investigate this chicken-and-egg puzzle using a $300,000 grant from the National Science Foundation she won in September. The money will primarily be used to buy Bennert out of teaching time, since she said during a regular quarter she has “zero time to do research.”
Bennert and the students are using data from three telescopes: the Keck Telescope in Hawaii, the smaller Lick Telescope in San Jose and the Hubble Space Telescope.
“The nice thing with the universe is that telescopes can be used as time machines,” Bennert said. “So if you look at the sun now, you see it as it was eight minutes ago, because it’s so far away that it took the light eight minutes to reach us. And the sun is our closest star. The farther we look out in space, the farther we look out in time.”
After calculating the masses of black holes and their galaxies in faraway universes, Bennert’s team will compare their results to nearby galaxies. Whichever has a bigger mass than expected, galaxies or black holes, likely came first.
Bennert cites the weather as one of the project’s challenges.
“I don’t know how many nights we’ve had on this project already, and it was only the last time I was (in Hawaii) a month ago that we were finally successful in getting some data,” she said. “There’s always this unpredictability on whether the weather will cooperate.”
Another potential obstacle is the vast distance that separates Bennert’s team and the galaxies they are trying to analyze.
“I think the project is challenging — it is by necessity, because if it wasn’t, someone would have already done it,” she said. “We are looking at galaxies billions of years away, at a time when the universe was very young, so the main challenge I anticipate is will my data be deep enough to analyze it? Will I be able to see the host galaxy, will the Hubble Space Telescope images not be deep enough?”
But if Bennert succeeds, scientists will be one step closer to understanding space’s secrets.
“Astronomy is typically based on human curiosity, to just want to know what is out there,” Bennert said. “We are trying to solve the mysteries of the universe.”