You hurtle through space, barreling toward the center of the Milky Way galaxy. A cosmic traveler, you shed the confines of human speed. As you reach our galaxy’s heart, you see it. Sagittarius A, our galactic center, a supermassive black hole. 

The black hole is visible as negative space around which the accretion disk swirls in a chaotic, fiery fashion. Plasma particles shoot out in jets from its polar regions.    

You move under the unmistakable pull of the black hole’s gravity. You fall toward the event horizon, pass its threshold and shoot toward the singularity. At this point, it’s inescapable. 

“Once you’re inside the black hole, your timeline is pointed inwards,” said Brenna Mockler, an assistant professor in the Department of Physics and Astronomy at the College of Letters and Science at UC Davis. “Light can’t escape anymore, so all the photons are moving inwards. You’re also moving inwards.”      

What would it feel like to fall into a black hole? 

How might falling into a black hole feel? Assuming you’re not ripped apart, a process called spaghettification, and your consciousness remains intact, Mockler has some ideas. 

“Your concept of time is going to be different from everyone else’s, and I think they did a really good job in Interstellar of emphasizing that particular aspect,” Mockler said, noting a segment of the film when the protagonist experiences time dilation when traveling close to a fictional black hole called Gargantua. “If you get closer to the black hole and then you return to other people, it’s similar to if you’re moving at close to the speed of light, your time is going at a different pace from everyone else’s.”

And what happens when you cross the event horizon?

“You’re still looking out at the galaxy even as you’re falling in,” Mockler said. “Light can’t get out, but light can get in, so if you could stop falling for a moment and let the light catch up to you, you would actually see things that are happening far away.

Of course, the above is all theoretical. No one knows what happens when an object falls into a black hole. For Mockler, it’s a fun thought experiment informed by the mathematics underlying astrophysics. 

“A black hole is a much more extreme object than anything we find on Earth,” she said. “There’s a drama and a beauty to it that’s exciting to me.” 

A homegrown curiosity for the cosmos

Currently finishing up a fellowship at the Carnegie Theoretical Astrophysics Center in Pasadena, Calif., Mockler will join the UC Davis campus in summer 2026. The move is a homecoming.

Mockler was raised in Davis, and it was while she was attending Ralph Waldo Emerson Junior High that her fascination with space was ignited. 

“I specifically remember my seventh-grade teacher, Mr. Phillips, doing a unit about astronomy and just letting us ask questions about anything, and we talked one day about black holes,” Mockler said. “I still have that memory today; it was such an amazing class.”    

Mockler later studied physics at Cornell University and eventually earned a Ph.D. in astronomy and astrophysics from UC Santa Cruz in 2022. 

“My research focuses on the growth and evolution of the supermassive black holes that live at the centers of most galaxies and also on how their evolution affects the life of the galaxy around them,” she said.  

How black holes shape the galaxies around them 

Black holes don’t just devour cosmic material. When gas is eaten by them, they produce copious amounts of energy. This output affects the local environment, influencing how the surrounding galaxy evolves.   

“Most of the time, if we’re trying to study a black hole, we can only really do it through the gravitational influence it has on the mass orbiting around it,” Mockler said. “If it rips apart a star, the gas from the star will briefly feed the black hole at a very high rate. As the black hole eats the star, the gas from the star lights up the region around it, and we can suddenly learn a lot more about its properties.” 

The tides of a star devourer

Black holes are prevalent in the universe. It’s thought that supermassive black holes exist at the heart of every large galaxy with masses millions to billions of times the size of our sun. 

But smaller black holes also exist. The smallest black holes, which are usually 100 solar masses or less, are called stellar mass black holes.

“Those are black holes that we think were formed from an explosion or implosion of a star,” Mockler said. “To get from the stellar mass black hole to the supermassive black holes, you have to grow by many orders of magnitude and that’s really difficult to do. We still don’t understand how that has happened so successfully for so many galaxies.” 

But a unique class of astrophysical events called tidal disruption events (TDEs) are providing researchers with clues. 

What are tidal disruption events? 

Similar in appearance and brightness to supernovae, TDEs occur when a star gets too close to a black hole and is devoured by it. According to Mockler, TDEs tend to occur around lower mass supermassive black hole systems, because larger mass supermassive black holes are more likely to swallow the star whole before it can be tidally disrupted and produce a bright flare.  

“What happens to the star as it gets close to the black hole is it experiences tidal forces the same as our Earth experiences from the sun and the moon,” Mockler said. “It’s the same physical calculation; it’s just a much stronger source of gravity.” 

When this happens to a star, its ball-like shape is stretched as it experiences tidal oscillations. Eventually, the gravity of the black hole overwhelms the self-gravity of the star and rips it apart, leading to a brilliantly luminescent TDE.    

Studying black holes through light and X-rays

Usually, TDEs are detected by astronomers in optical wavelengths, visible by observation. But Mockler is currently interested in identifying TDEs that also exhibit X-ray wavelengths.

“The reason it’s exciting when they have X-rays is because you’re probably looking more at the light that’s coming out from closer to the actual black hole,” she said. “We actually don’t have that many events that have both optical and X-ray data, especially at early times when the accretion disk is just starting to form.” 

To help rectify this, Mockler has conducted theoretical modeling that she hopes will help observers identify and explain TDEs that have emissions at optical and X-ray wavelengths. The research could help us understand how emissions at these very different wavelengths are connected and how the accretion disks that power the growth of supermassive black holes form.

New optical surveys like the Legacy Survey of Space and Time (part of the Vera Rubin Observatory, which was developed in part at UC Davis) will find thousands of new optical TDEs. X-ray telescopes, such as  NASA’s Swift and Chandra telescopes as well as the new Einstein Probe, will look for X-ray emissions from the same events.

“We’re going to see if we can try to connect the processes close to the black hole to the emissions that we see from most of these tidal disruption events,” Mockler said. 

Doing so will help make these cosmic devourers and their evolution more understandable.