A Survey of Hubble’s Deepest Look Back into Time Uncovers New Clues.
The universe seems to be teeming with black holes—cosmic phenomena that devour anything that ventures too close. The most enormous of these, with masses millions or even billions of times greater than our Sun, are found at the centers of galaxies. When these supermassive black holes actively consume nearby matter, they can shine brightly as active galactic nuclei. However, not all black holes exhibit constant activity; some show variability, flickering in and out of brightness like erratic holiday lights.
Astronomers have used this variability to track down black holes, with the Hubble Ultra Deep Field proving to be an exceptional site for such investigations. This region, captured in a profound image released in 2004, revealed faint galaxies from shortly after the Big Bang. By analyzing more recent images of this field, a team from Stockholm University observed fluctuations in brightness among certain galaxies, which they attribute to the variability of black holes. This finding suggests that there may be more black holes in the early universe than previously known.
The interplay between early galaxies and massive black holes presents a classic cosmological dilemma: which came first? The Hubble Ultra Deep Field’s latest observations offer fresh insights into this ongoing mystery.
With the aid of NASA’s Hubble Space Telescope, an international team of researchers, led by scientists from Stockholm University’s Department of Astronomy, has discovered a greater number of black holes in the early universe than previously reported. This finding provides crucial insights into the formation of supermassive black holes.
The origins of the first black holes, which emerged shortly after the Big Bang, remain unclear. Although supermassive black holes—some weighing more than a billion Suns—were observed at the centers of several galaxies less than a billion years after the Big Bang, their early formation processes are not well understood.
Alice Young, a PhD student at Stockholm University and co-author of the study published in The Astrophysical Journal Letters, remarked, “Many of these objects seem to be more massive than we originally thought they could be at such early times—either they formed very massive or they grew extremely quickly.”
Black holes significantly influence galaxy evolution, but uncertainties persist about their role. To better understand the connection between black hole and galaxy evolution, the team used Hubble to survey black holes in faint galaxies from when the universe was just a few percent of its current age. By re-photographing the survey area after several years, they could measure variations in galaxy brightness—indicative of black holes—and identified more than previous methods had.
The new observations suggest that some early black holes likely formed from the collapse of massive, pristine stars in the first billion years, as later-generation stars were affected by the remnants of previous stellar generations. Other possible formation mechanisms include collapsing gas clouds, mergers of stars in massive clusters, and speculative primordial black holes formed in the Big Bang’s initial seconds. This information will help refine models of galaxy formation.
Matthew Hayes from Stockholm University’s Department of Astronomy and lead author of the study, stated, “The formation mechanism of early black holes is an important part of the puzzle of galaxy evolution. With accurate models of how black holes formed from collapsing massive stars, we can better understand galaxy evolution.”
Astronomers are also using NASA’s James Webb Space Telescope to search for early galactic black holes, aiming to understand their mass and locations.
The Hubble Space Telescope, operational for over three decades, continues to provide groundbreaking discoveries that enhance our understanding of the universe. The Hubble mission is a collaborative effort between NASA and the European Space Agency (ESA), managed by NASA’s Goddard Space Flight Center and supported by Lockheed Martin Space. The Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, handles Hubble’s science operations for NASA.
