Using the Hubble Space Telescope, an international team of researchers led by scientists from the Department of Astronomy at Stockholm University has discovered more black holes in the early Universe than previously reported. The new result may help scientists understand how supermassive black holes appeared.
Currently, scientists do not have a complete picture of how the first black holes formed shortly after the Big Bang. It is known that supermassive black holes, which can weigh more than a billion suns, exist in the center of several galaxies less than a billion years after the Big Bang.
Black holes and galaxies
“Many of these objects seem to be more massive than we originally thought they could be at such an early time – either they formed very massive or grew extremely fast,” says Alice Young, a PhD student at Stockholm University and co-author of the study published in The Astrophysical Journal Letters.
Black holes play an important role in the life cycle of all galaxies, but there is a great deal of uncertainty in our understanding of how galaxies evolve. To get a complete picture of the connection between the evolution of galaxies and black holes, the researchers used Hubble to find out how many black holes existed among the population of faint galaxies when the age of the Universe was only a few percent of its current age.
The initial observations of the study area were re-imaged by Hubble a few years later. This allowed the team to measure variations in the brightness of the galaxies. These variations are a characteristic feature of black holes. The team discovered more black holes than had previously been found using other methods.
NASA, ESA, M. Hayes (Stockholm University), J. DePasquale (STScI)
Collapse of massive stars
New observational results suggest that some black holes were probably formed as a result of the collapse of massive, pristine stars during the first billion years of cosmic time. These types of stars can only exist in the very early stages of the Universe’s development, as later generations of stars are contaminated by the remnants of stars that have already lived and died.
Other alternatives to black hole formation include the collapse of gas clouds, the merging of stars into massive clusters, and “primordial” black holes that formed (through physically speculative mechanisms) in the first few seconds after the Big Bang. Thanks to this new information about the formation of black holes, it is possible to build more accurate models of galaxy formation.
“The mechanism of early black hole formation is an important part of the puzzle of galaxy evolution,” says Matthew Hayes from the Department of Astronomy at Stockholm University and lead author of the study, “Together with models of black hole growth, calculations of galaxy evolution can now be put on a more physically motivated basis, with an accurate picture of how black holes emerged from collapsing massive stars.
Astronomers are also conducting observations using the James Webb Space Telescope to search for galactic black holes that formed shortly after the Big Bang to understand how massive they were and where they are located.
