Regular high-energy pulses of gamma-ray radiation emerging from around the Milky Way's central black hole may be coming from a blob of matter whipping around at 30% the speed of light.
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Regular high-energy pulses of gamma-ray radiation emerging from around the Milky Way's central black hole may be coming from a blob of matter whipping around at 30% the speed of light. |
Something near the supermassive black hole at the heart of
the Milky Way has been firing regular blasts of high-energy gamma-rays toward
Earth, and scientists may finally know what it is.
In new non-peer-reviewed research posted to the preprint
server arXiv, a duo of astrophysicists at the National Autonomous University of
Mexico conclude that the bursts of radiation are emanating from a blob of gas
spinning around the black hole at almost one-third the speed of light. The
team's findings may solve a mystery regarding the Milky Way's central black
hole — formally named Sagittarius A* (Sgr A*) and located around 26,700
light-years from Earth — that has perplexed astronomers for two years.
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A view of the mysterious X-ray emissions spotted near the
Milky Way's central black hole. These may be related to new gamma-ray
detections from the same region. (Image credit: NASA/JPL-Caltech) |
The gamma-ray radiation pulses from around Sgr A* were first
detected belting Earth in 2021. The team behind the observation knew that the
radiation couldn't be coming from within the supermassive black hole itself,
however.
That's because all black holes are bound by a region called
an event horizon, which marks the point beyond which nothing, not even light,
has the velocity needed to escape the black hole's immense gravity. This means
black holes don't emit radiation themselves, so the gamma-rays must be coming
from the environment of Sgr A*.
Other supermassive black holes are known to emit powerful
radiation from their immediate surroundings when their gravitational influence
generates turbulent conditions in surrounding gas and dust, forming a structure
called an accretion disk. As black holes feed on this matter, the accretion
disk emits light that spans the electromagnetic spectrum, from low-energy radio
waves to high-energy gamma-rays.
This can't account for the gamma-rays from Sgr A*, however,
as the Milky Way's black hole is surrounded by very little matter and is
feeding so slowly that it would be equivalent to a human living on a diet of
one grain of rice every million years, according to University of Arizonaastronomer Chris Impey, who was not involved in the research.
Using data from the Fermi Gamma-ray Space Telescope
collected between June and December 2022, the researchers aimed to discover the
origin of these gamma-rays.
The duo searched the publicly available Fermi data for
patterns of periodicity in the gamma-ray emissions. They found that the pulses
emerge from close to Sgr A* roughly once every 76.32 minutes. This period of
emission is half the time between pulses of X-ray radiation also seen coming
from the vicinity of the Milky Way's supermassive black hole, suggesting the
two emissions are in harmony and are likely related.
"The coincidence of the multiwavelength periodicity in
X-ray and gamma-ray points towards a single physical mechanism that produces
it," the team wrote in the paper.
This revelation of what the researchers call a "unique
oscillatory physical mechanism" led them to conclude that both the
gamma-rays and the X-rays are being emitted by a "blob" of gas that
is swirling around Sgr A* at around 30% the speed of light — or around 200
million mph (320 million km/h). They think this speeding lump of matter is
emitting light across several wavelengths of radiation as it swirls around Sgr
A*, flaring periodically as its orbit proceeds.
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