For many years, astronomers have categorized black holes into three main groups. The first group consists of stellar-mass black holes, which range from five to 50 times the mass of our Sun. Then, there are supermassive black holes (SMBHs), which are millions to billions of times more massive than the Sun. Finally, there are intermediate black holes (IMBHs) with masses falling in between.

While stellar mass black holes and SMBHs have been observed frequently, evidence of IMBHs has been scarce. This has created a gap in our understanding of black hole evolution, as IMBHs are believed to be the link between stellar black holes and SMBHs as they grow.

In a series of recent studies, an international team led by researchers from Vanderbilt University's Lunar Labs Initiative (LLI) has potentially discovered these elusive IMBHs.

In one study, astronomers Krystal Ruiz-Rocha and Anjali Yolkier reanalyzed data from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo Collaboration to search for signs of IMBH mergers. The results suggest that these observatories detected gravitational wave events corresponding to mergers of black holes ranging from 100 to 300 solar masses, placing them in the range expected for lightweight IMBHs.

Astronomer and senior author Karan Jani describes black holes as 'the ultimate cosmic fossils' and highlights the significance of this new population of black holes in shedding light on the early stars of our Universe.

Related research demonstrates how the upcoming Laser Interferometer Space Antenna (LISA) mission, set to launch in the late 2030s, could validate these findings. Unlike LIGO and Virgo, LISA will be able to track black holes for years before they merge, providing valuable insights into their origin and evolution.

The team plans to investigate how IMBHs could be observed using gravitational wave observatories on the Moon, aligning with NASA's exploration plans as part of the Artemis program's long-term objectives. This initiative aims to build on past lunar experiments and integrate scientific frontiers with space exploration.

This groundbreaking research is documented in The Astrophysical Journal Letters, with additional supporting studies published in The Astrophysical Journal.