"We're showing this indian," said Todd Thompson, lead author and professor of astronomy at The Ohio State University.
Black holes can form after stars, collapse and explode, creating gravitational whirls. They can be found at the center of galaxies, acting like a supermassive engine.
But that's not always the case. When some stars die and collapse, they form neutron stars, which are small and incredibly dense.
Astronomers can learn about the evolution of the stars and the black hole formation.
But if astronomers only focus on supermassive black holes, like the one at the center of our galaxy, and neutron stars, they're missing all the demographics of the population, the researchers said. They compare it to census takers.
"People are trying to understand supernova explosions, how supermassive black stars explode, how the elements were formed in supermassive stars," Thompson said. "So if we can reveal a new population of black holes, it would tell us more about which explode, which don't, which form black holes, which form neutron stars. It opens up a new area of study."
Black holes are often found in binary systems, where two stars orbit – like the twin suns we see on Tatooine in the "Star Wars" films.
If one star dies, the other still, or even the neutron star.
Until this study, astronomers found black holes that clocked in between five and 15 times. But a neutron star. Then, that black hole would grow.
LIGO spotted two black holes merging into one galaxy 1.8 million light-years away. The two monstrous black holes were 31 times the mass of the sun and 25 times its mass, respectively.
"Immediately, everyone was like 'wow,' because it was such a spectacular thing," Thompson said. "Not only because it proved that LIGO worked, but because the masses were HUGE. Black holes are a big deal to you – we hadn't seen them before."
This expanded range of black holes, suggesting they could be larger. But what about those were smaller, existing between the boundary of neutron stars and black holes?
Thompson and his colleagues turned to APOGEE data. It's the Apache Point Observatory Galactic Evolution Experiment, which has observed light from 100,000 stars in the Milky Way.
They looked to see if the wavelengths of the stars suggested a fellow companion that was otherwise invisible. If they showed a change in wavelength, going from blue to red, it might suggest that the companion had turned into a black hole.
Thompson and his colleagues have found a giant red star or something.
The potential low-mass black hole is 3.3 times the mass of our sun. Previously, the smallest black hole was discovered 3.8 times the mass of our sun.
"What we've done here is a new class of low-mass black holes that astronomers hadn't previously known about," "Thompson said. "The masses of things tell us about their formation and evolution, and they tell us about them."