Using data from NASA's Great Observatories, astronomers have found the
best evidence yet for cosmic seeds in the early universe that should
grow into supermassive black holes.
Researchers combined data from NASA's
Chandra X-ray Observatory, Hubble Space Telescope and Spitzer Space
Telescope to identify these possible black hole seeds.
"Our discovery, if confirmed,
explains how these monster black holes were born", said Fabio Pacucci of
Scuola Normale Superiore (SNS) in Pisa, Italy, who led the study.
"We found evidence that supermassive black hole seeds can form directly
from the collapse of a giant gas cloud, skipping any intermediate
steps".
Scientists believe a supermassive
black hole lies in the center of nearly all large galaxies, including
our own Milky Way. They have found that some of these supermassive
black holes, which contain millions or even billions of times the mass
of the sun, formed less than a billion years after the start of the
universe in the Big Bang.
One theory suggests black hole seeds
were built up by pulling in gas from their surroundings and by mergers
of smaller black holes, a process that should take much longer than
found for these quickly forming black holes.
These new findings suggest instead
that some of the first black holes formed directly when a cloud of gas
collapsed, bypassing any other intermediate phases, such as the
formation and subsequent destruction of a massive star.
"There is a lot of controversy over
which path these black holes take", said co-author Andrea Ferrara, also
of SNS.
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"Our work suggests we are narrowing in on an answer, where the black
holes start big and grow at the normal rate, rather than starting small
and growing at a very fast rate", Ferrara added.
The researchers used computer models
of black hole seeds combined with a new method to select candidates for
these objects from long-exposure images from Chandra, Hubble and
Spitzer.
The team found two strong candidates
for black hole seeds. Both of these matched the theoretical
profile in the infrared data, including being very red objects, and they
also emit X-rays detected with Chandra. Estimates of their
distance suggest they may have been formed when the universe was less
than a billion years old.
"Black hole seeds are extremely hard
to find and confirming their detection is very difficult", said Andrea
Grazian, a co-author from the National Institute for Astrophysics in
Italy. "However, we think our research has uncovered the two best
candidates to date".
The team plans to obtain further
observations in X-rays and infrared to check whether these objects have
more of the properties expected for black hole seeds. Upcoming
observatories, such as NASA's James Webb Space Telescope and the
European Extremely Large Telescope, will aid in future studies by
detecting the light from more distant and smaller black holes.
Scientists currently are building the theoretical framework needed to
interpret the upcoming data, with the aim of finding the first black
holes in the universe.
"As scientists, we cannot say at this
point that our model is 'the one'", said Pacucci. "What we really
believe is that our model is able to reproduce the observations without
requiring unreasonable assumptions".
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