This image of a special object, dubbed the “X-ray
dot,” represents a discovery from Chandra that could help explain the nature of
a mysterious class of sources in the early Universe. The optical and infrared
image from Hubble show the region around the X-ray dot, while the Chandra X-ray
image shows the close up. Prior to this discovery, “little red dots” seen by
the Webb telescope had not been known to emit X-rays. This one does, which
leads researchers to propose that the X-ray dot represents a previously unknown
transition phase of growing supermassive black holes.
X-ray: NASA/CXC/Max Plank Inst./R. Hviding et al.;
Optical/IR; NASA/ESA/STScI/HST; Image Processing: NASA/CXC/SAO/N. Wolk
A newly discovered object may be a key
to unlocking the true nature of a mysterious class of sources that astronomers
have found in the early universe in recent years.
A “X-ray dot” found by NASA’s Chandra
X-ray Observatory could explain what the hundreds or potentially thousands of
these objects are. A paper describing the results published in The
Astrophysical Journal Letters.
Shortly after NASA’s James Webb Space
Telescope started its science observations, reports of a new class of
mysterious objects emerged. Astronomers found small, red objects about 12
billion light-years from Earth or farther, which became known as “little red
dots” (LRDs).
Many scientists think LRDs are
supermassive black holes embedded in clouds of dense gas, which mask some of
the typical signatures in different kinds of light – including X-rays – that
astronomers usually use to identify them. This would make them different from
typical growing supermassive black holes, which are not embedded in dense gas,
allowing bright ultraviolet light and X-rays from material orbiting the black
holes to escape.
Because of this and their potential
similarities to stellar atmospheres, astronomers have called this the “black
hole star” scenario for LRDs.
This new “X-ray dot” (officially known
as 3DHST-AEGIS-12014), which is located about 11.8 billion light-years from
Earth, may provide a crucial bridge between black hole stars and typical
growing supermassive black holes. It exhibits most of the features of an LRD,
including being small, red, and located at a vast distance, but it glows in
X-ray light, unlike other LRDs.
“Astronomers have been trying to figure
out what little red dots are for several years,” said lead author Raphael
Hviding of the Max Planck Institute for Astronomy in Germany. “This single
X-ray object may be – to use a phrase – what lets us connect all of the dots.”
Artist's Illustration of a Close-Up View of X-ray Dot,
3DHST-AEGIS-12014.
NASA/CXC/SAO/M. Weiss; adapted by K. Arcand & J.
Major
The team found this one special object
after comparing new data from Webb with a deep survey previously performed by
Chandra.
“If little red dots are rapidly growing
supermassive black holes, why do they not give off X-rays like other such black
holes?” said co-author Anna de Graaff of the Center for Astrophysics | Harvard
& Smithsonian, in Cambridge, Massachusetts. “Finding a little red dot that
looks different from the others gives us important new insight into what could
power them.”
The researchers suggest that the X-ray
dot represents a transition phase from an LRD to a typical growing supermassive
black hole. As the black hole star consumes its surrounding gas, patchy holes
in the clouds of gas appear. This allows X-rays from material falling onto the
black hole to poke through, which are observed by Chandra. Eventually all the
gas is consumed, and the black hole star ceases to exist.
There are also hints in the Chandra data
of the X-ray dot that there are variations in X-ray brightness, which supports
the idea that the black hole is partly obscured. As the cloud of gas rotates,
patches of denser and less dense gas can move across the black hole, causing
changes in X-ray brightness.
“If we confirm the X-ray dot as a little
red dot in transition, not only would it be the first of its kind, but we may
be seeing into the heart of a little red dot for the first time,” said
co-author Hanpu Liu of Princeton University in New Jersey. “We would also have
the strongest piece of evidence yet that the growth of supermassive black holes
is at the center of some, if not all, of the little red dot population.”
An alternate idea for the X-ray dot is
that it is a more common type of growing supermassive black hole but is veiled
in an exotic type of dust that astronomers have not seen before. Future
observations are planned that should be able to shed light on the truth.
“The X-ray dot had been sitting in our
Chandra survey data for over ten years, but we had no idea how remarkable it
was before Webb came along to observe the field,” said co-author Andy Goulding
of Princeton. “This is a powerful example of collaboration between two great
observatories.”
NASA's Marshall Space Flight Center
manages the Chandra program. The Smithsonian Astrophysical Observatory's
Chandra X-ray Center controls science operations from Cambridge, Massachusetts,
and flight operations from Burlington, Massachusetts.
Read more from NASA’s Chandra X-ray Observatory
Learn more about the Chandra X-ray
Observatory and its mission here: https://science.nasa.gov/chandra
Source: NASA Connects Little Red Dots with Chandra, Webb - NASA Science
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