Did scientists just settle the debate over supermassive black holes?
Italian astronomers argue black holes are born from the collapse of giant gas clouds, not stars.
X-ray Credit:NASA/CXC/Scuola Normale Superiore/F. Pacucci, et al. Optical Credit: NASA/STScI Illustration Credit: NASA/CXC/M. Weiss
Black holes may be born even bigger than we thought.
A new analysis of telescope data by astrophysicists at a university in Pisa, Italy supports theories that the most massive black holes astronomers know of, which could be billions of times more massive than the sun, are actually born big – as a result of the collapse of a giant gas cloud, rather than a star.
"There is a lot of controversy over which path these black holes take," explained Andrea Ferrara, an astrophysicist at Scuola Normale Superiore in Pisa, in an announcement.
If his team's findings are right, they could help explain how supermassive black holes, the mysterious energy vortices thought to lie at the heart of most large galaxies, formed within a billion years of the birth of the universe 13.8 billion years ago.
This theory presents a contrast to widely accepted models of black holes growing over time by pulling in gas from their surroundings and by mergers of smaller “stellar-mass” black holes, which form by the collapse of massive stars.
"Our work suggests ... black holes start big and grow at the normal rate, rather than starting small and growing at a very fast rate," he said.
The authors argue that the gravitational monsters that swallow matter, gas, and even light could not have grown to their monstrous size in the short amount of time – by cosmic standards – they took to form.
Ferrara and his colleagues will report their findings in the upcoming issue of the Monthly Notices of the Royal Astronomical Society.
They combed data and images collected by NASA's Chandra X-ray Observatory, the Hubble Space Telescope, and the Spitzer Space Telescope to identify what appear to be black hole “seeds,” or baby black holes. They matched the images with their own modeling that predicted the type of light massive black hole seeds should emit.
Two objects met their requirements, emitting the infrared and X-ray signals they expected to see left over in the universe as remnants of massive black hole seeds formed billions of years ago, rather than the much smaller stellar-mass black hole seeds.
Both of the potential seeds were about 100,000 times the mass of our sun, the researchers calculated, and they formed less than 1 billion years after the Big Bang, as Space.com reports. This size and age indicated to the Italian team that, at least in the early universe, supermassive black holes started out large, simply with the collapse of giant gas clouds.
Though more research is needed before these findings make their way into astronomy textbooks, the new research is really promising, says Priyamvada Natarajan, a black hole expert who teaches astronomy and physics at Yale University.
“This is super exciting,” Prof. Natarajan told The Christian Science Monitor in a phone interview. “It’s an old theoretical idea, but it’s the first observational hint that we might be able to pick out the first black holes that formed from massive seeds,” she said.
Theoretical physicists, including Natarajan’s team, had already suggested that supermassive black holes start as large seeds formed by the collapse of giant gas clouds in a series of papers between 2006 and 2008, but nobody had looked at data from telescopes to back this up.
Other astronomers are more skeptical.
Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, points out that the observational data presented in the study could be interpreted in other ways.
“They are putting a lot of weight on the mere detection of X-rays from these objects,” Dr. McDowell wrote in an e-mail to the Monitor. “It's interesting, but, you know what Carl Sagan said about extraordinary claims and extraordinary evidence,” he wrote.
The next opportunity to study these seeds and the new model in more detail will be after the 2018 launch of NASA’s next-generation James Webb Space Telescope, which will detect faint light from more distant and smaller black holes.