Sagittarius A*, the supermassive black hole at the center of the Milky Way galaxy, is far less luminous than other black holes at the centers of galaxies we can observe, which means our galaxy’s central black hole has not been actively gobbling up material around it. Yet new evidence from NASA’s IXPE (Imaging X-ray Polarimetry Explorer) telescope suggests the ancient sleeping giant woke recently – about 200 years ago – to devour gas and other cosmic detritus within its reach.
Sagittarius A* is more than 25,000 light
years from Earth – our nearest supermassive black hole, with an estimated mass
millions of times that of our Sun. Often abbreviated by researchers to Sgr A*
(pronounced "Sagittarius A star"), it sits in the constellation of
Sagittarius at the very heart of the Milky Way.
Imagery from NASA’s Imaging X-ray Polarimetry Explorer and Chandra X-ray Observatory have been combined to show X-ray data of the area around Sagittarius A*, the supermassive black hole at the core of the Milky Way galaxy. The lower panel combines IXPE data, in orange, with Chandra data in blue. The upper panel depicts a much wider field-of-view of the center of the Milky Way, courtesy of Chandra. The thin white lines layered onto the top panel frame the highlighted area, and indicate that the perspective in the bottom panel has been rotated approximately 45 degrees to the right. The combination of IXPE and Chandra data helped researchers determine that the X-ray light identified in the molecular clouds originated from Sagittarius A* during an outburst approximately 200 years ago. Credits: IXPE: NASA/MSFC/F. Marin et al; Chandra: NASA/CXC/SAO; Image Processing: L.Frattare, J.Major & K.Arcand
Scientists called on IXPE for a
closer look when previous X-ray studies detected relatively recent X-ray
emissions of giant clouds of gas in its vicinity. Given that most cosmic
clouds, called “molecular clouds,” are cold and dark, the X-ray signatures of
these clouds should have been faint. Instead, they shone brightly.
“One of the scenarios to explain
why these giant molecular clouds are shining is that they are, in fact, echoing
a long-gone flash of X-ray light, indicating that our supermassive black hole
was not that quiescent some centuries ago,” said Frédéric Marin, astronomer at
the Astronomical Observatory of Strasbourg in France and lead author of the new
study, published in the journal Nature.
IXPE, which measures polarization
of X-ray light, or the average direction and intensity of the electric field of
light waves, pointed at these molecular clouds for two periods of study in
February and March 2022. When astronomers combined the resulting data with
images from NASA’s Chandra X-ray
Observatory and
compared them to archival observations from the European Space Agency’s XMM-Newton mission, they could isolate the reflected
X-ray signal and discover its point of origin.
“The polarization angle acts like a
compass, pointing us toward the mysterious, long-gone source of illumination,”
said Riccardo Ferrazzoli, astrophysicist at the Italian National Institute of
Astrophysics in Rome. “And what lies in that direction? None other than Sgr
A*.”
Analyzing the data, the team
figured out that the X-rays from the giant molecular clouds were reflected
light from an intense, short-lived flare produced at or near Sgr A*, possibly
caused by the black hole abruptly consuming nearby material.
The data also helped researchers estimate
the luminosity and duration of the original flare – suggesting the event
occurred some 200 Earth years ago, or roughly around the start of the 19th
century.
The team’s next goal is to repeat the observation and reduce the uncertainties of the measurement, said Steven Ehlert, IXPE project scientist at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Combined images of Sagittarius A*, the supermassive black hole at the center of the Milky Way galaxy, enabled researchers to develop a sonification, or an adaptation of visual information into audible, even musical sounds. In this sonification, adapting data from NASA’s Imaging X-ray Polarimetry Explorer and Chandra X-ray Observatory, an arched line ripples across the image, starting at the lower righthand corner. As it passes over the orange-tinted IXPE data, sounds like digital winds are triggered, particularly where those orange areas are brightest. When the traveling line passes the blue-tinted Chandra data, the resulting notes resemble steel drums. Learn more about these cosmic harmonies here. Credits: NASA/CXC/SAO/K.Arcand, SYSTEM Sounds—M. Russo, A. Santaguida
Follow-up data could improve
estimations of when the flare occurred and how intense it may have been at its
peak, and will help determine the three-dimensional distribution of the giant
molecular clouds surrounding the quiescent black hole.
Most importantly, he said, such
studies help researchers gain new understanding of the physical processes
necessary to awaken Sgr A* again – even if just temporarily – from its uneasy
slumber.
“IXPE is playing a key role in
helping us better understand the timescale on which the black hole at the
center of our galaxy is changing,” Ehlert said. “We know change can happen to
active galaxies and supermassive black holes on a human timescale. We’re
learning more about this one’s behavior over time, its history of outbursts, and
we’re eager to observe it further to determine which changes are typical and
which are unique.”
IXPE is a collaboration between NASA and the Italian Space Agency with partners and science collaborators in 12 countries. IXPE is led by Marshall. Ball Aerospace, headquartered in Broomfield, Colorado, manages spacecraft operations together with the University of Colorado's Laboratory for Atmospheric and Space Physics in Boulder.
Source: Milky Way’s Central Black Hole Awoke 200 Years Ago, NASA’s IXPE Finds | NASA
No comments:
Post a Comment