NASA/CXC/M.Weiss
This artist’s illustration depicts the findings of a new study about
the supermassive
black hole at the center of our galaxy called Sagittarius A* (abbreviated as Sgr
A*). As reported in our latest press release, this result found that Sgr A* is spinning so quickly that it is
warping spacetime — that is, time and the three dimensions of
space — so that it can look more like a football.
These results were made with NASA’s Chandra X-ray Observatory and the NSF’s Karl G. Jansky Very Large Array
(VLA). A team of researchers applied a new method that uses X-ray and radio data to determine how quickly Sgr A* is spinning
based on how material is flowing towards and away from the black
hole. They found
Sgr A* is spinning with an angular velocity that is about 60% of the maximum
possible value, and with an angular
momentum of about
90% of the maximum possible value.
Black holes have two fundamental
properties: their mass (how much they weigh) and their spin (how
quickly they rotate). Determining either of these two values tells scientists a
great deal about any black hole and how it behaves. In the past, astronomers
made several other estimates of Sgr A*’s rotation speed using different
techniques, with results ranging from Sgr A* not spinning at all to it spinning
at almost the maximum rate.
The new study suggests that Sgr A*
is, in fact, spinning very rapidly, which causes the spacetime around it to be
squashed down. The illustration shows a cross-section of Sgr A* and material
swirling around it in a disk. The black sphere in the center represents the
so-called event
horizon of the
black hole, the point of no return from which nothing, not even light, can
escape.
Looking at the spinning black hole
from the side, as depicted in this illustration, the surrounding spacetime is
shaped like a football. The faster the spin the flatter the football.
The yellow-orange material to
either side represents gas swirling around Sgr A*. This material inevitably
plunges towards the black hole and crosses the event horizon once it falls
inside the football shape. The area inside the football shape but outside the
event horizon is therefore depicted as a cavity. The blue blobs show jets firing away from the poles of the spinning black
hole. Looking down on the black hole from the top, along the barrel of the jet,
spacetime is a circular shape.
A black hole’s spin can act as an important source of energy. Spinning supermassive black holes produce collimated outflows such as jets when their spin energy is extracted, which requires that there is at least some matter in the vicinity of the black hole. Because of limited fuel around Sgr A*, this black hole has been relatively quiet in recent millennia with relatively weak jets. This work, however, shows that this could change if the amount of material in the vicinity of Sgr A* increases.
Chandra X-ray image of Sagittarius A* and the surrounding region. NASA/CXC/Univ. of Wisconsin/Y.Bai, et al.
To determine the spin of Sgr A*, the authors used an empirically based
technique referred to as the “outflow method” that details the relationship
between the spin of the black hole and its mass, the properties of the matter
near the black hole, and the outflow properties. The collimated outflow
produces the radio waves, while the disk of gas surrounding the black hole is
responsible for the X-ray emission. Using this method, the researchers combined
data from Chandra and the VLA with an independent estimate of the black hole’s
mass from other telescopes to constrain the black hole’s spin.
The paper describing these results
led by Ruth Daly (Penn State University) is published in the January 2024 issue
of the Monthly Notices of the Royal Astronomical Society and appears online
at https://ui.adsabs.harvard.edu/abs/2024MNRAS.527..428D/abstract. The other authors are Biny Sebastian (University of
Manitoba, Canada), Megan Donahue (Michigan State University), Christopher O’Dea
(University of Manitoba), Daryl Haggard (McGill University) and Anan Lu (McGill
University).
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.
For more Chandra images, multimedia and related materials, visit: https://www.nasa.gov/mission/chandra-x-ray-observatory/
Visual Description:
This artist’s illustration shows a
cross-section of Sagittarius A*, pronounced as “SAJ-ee-TARE-ee-us A-star”, the
supermassive black hole near the center of our Milky Way galaxy.
In the middle of the image, the
spinning, circular black hole is presented from the side in black. The shape of
the surrounding spacetime, pictured in shades of dark yellow, looks as though
it has been squashed down, thus resembling the shape of an American football.
The swirling gas that surrounds Sagittarius A* is presented on either side of
the black hole, within a rectangular-shaped dotted line, indicating the
representation is a cross-section view.
The background of the image contains a multitude of faint stars, peeking out from within brooding, dark red, indistinct clouds.
Source: Telescopes Show the Milky Way's Black Hole is Ready for a Kick - NASA
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