A homework project in a University of Texas astronomy course, conducted collaboratively between the Austin and San Antonio campuses, culminated in students making a discovery published in a scientific journal. Researchers previously thought Segue 1, a small galaxy located 75,000 light-years from the Milky Way, was abundant in dark matter, a type of matter that does not interact with light. Some scientists deemed it a significant site for studying this enigmatic substance.

However, a recent study indicates that the dim dwarf galaxy’s mass is predominantly derived from a newly identified supermassive black hole, rather than dark matter. This black hole, estimated to have a mass exceeding 450,000 suns, was uncovered by Nathaniel Lujan, a graduate student in San Antonio, through advanced computer modeling techniques acquired in his Galactic and Gravitational Dynamics class.

The discovery implies that enormous black holes may be more prevalent than previously considered, even in small galaxies, questioning astronomers’ grasp of the forces that maintain dwarf galaxies’ structure. “It’s astonishing,” remarked Lujan during a presentation at the American Astronomical Society meeting in Anchorage, Alaska, “because Segue 1 is a barely discernible galaxy, yet I’m proposing that it contains a half-million solar-mass supermassive black hole at its core.”

Segue 1, first documented in 2006 through the Sloan Digital Sky Survey telescope in New Mexico, does not possess a sufficient number of stars to uphold its gravitational integrity. Initially, scientists hypothesized that a dark matter halo was inhibiting its dispersal.

According to Karl Gebhardt, a UT Austin astronomy professor who co-instructed the class along with UT San Antonio’s assistant professor Richard Anantua, the students started examining Segue 1 as part of a homework assignment. Their intention was to illustrate how to conduct computer simulations to infer hidden phenomena.

Since Segue 1 was recognized for its dark matter, the class utilized it for their exercise. The professors split the students into three groups: one concentrated on dark matter, another incorporated a theoretical black hole, and the last examined the star count. Their aim was to ascertain which scenario most accurately reflected the true behavior of the stars within the system.

Initially, they eliminated stars from the galaxy’s outskirts that were affected by the Milky Way from their dataset to focus on those influenced solely by Segue 1’s gravity. Subsequently, they analyzed the velocity and trajectory of the remaining stars.

They discovered that stars close to the center moved in rapid, tight orbits, suggesting they were orbiting a black hole. Models that included the black hole provided the best match to Segue 1’s actual stellar movements.

“I didn’t anticipate that,” Gebhardt shared with Mashable. “I thought, ‘Alright, we need to document this.'”

The findings were recently published in The Astrophysical Journal Letters, with several students from the spring 2024 class acknowledged as coauthors.

Black holes are enigmatic regions in space characterized by gravitational forces so intense that not even light can escape. Just a few decades ago, their existence was uncertain, but in 2019, the Event Horizon Telescope captured the inaugural image of one in the Messier 87 galaxy, roughly 53 million light-years away. Instead of having a surface, black holes feature an “event horizon” — a boundary beyond which anything that crosses is lost indefinitely. Scientists capture images of black holes by photographing the glowing gas swirling around them and the shadow their gravity casts against that light.

An additional revelation for the class was the extraordinary size of the central black hole. Their models suggest it could be approximately 10 times the combined mass of all the stars in the dwarf galaxy. Generally, a galaxy’s stars outweigh the black hole.

“This might be because Segue 1 is essentially deceiving us,” Lujan stated. “It could have originated as a significantly larger galaxy, and due to its close encounters with the Milky Way, the Milky Way could have siphoned off gas and inhibited star formation within the galaxy.”

For his doctoral dissertation, Lujan intends to utilize advanced computers and artificial intelligence to conduct further simulations on other dwarf galaxies that were once thought to be dominated by dark matter.

Another potential explanation for Segue 1 is its similarity to a new type of galaxy identified by NASA’s James Webb Space Telescope. Scientists label these objects found in the early universe as “little red dots.” They appear to have formed with large black holes and minimal stars. One research group suggested they may be massive gas spheres encasing black holes, coining them “black hole stars.”

The study serves as a reminder that valuable insights can emerge by reevaluating past data, Gebhardt noted.

“What truly excites me is that these galaxies we are discovering, such as Segue 1, might be analogs to the early universe, where the black holes are exceptionally massive,” he remarked. “And so, regardless of whether we’ve considered thoroughly enough how to construct these entities, nature has indeed found a way.”