by NASA scientists have observed a stunning cosmic fossil that was created when a supermassive black hole erupted more than 5 million years ago.
The team at the space agency’s Goddard Space Flight Center used the X-ray Multiple Mirror Mission (XMM-Newton) space telescope with the help of NASA’s Chandra X-ray Observatory to detect the X-rays that outline the cold gas clouds in a relatively close distance. Spiral galaxy NGC 4945, 13 million light years away in the constellation Centaurus (the Centaurus).
The gas appears to have passed through the galaxy when it erupted around the central black hole, which has a mass equivalent to about 1.6 million suns and is currently feeding on the matter around it, fueling the bright galactic engine called the active galactic nucleus ( AGN). .
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This gas that has been disposed of by this supermassive black hole is the raw material that collapses to create stars. These findings could therefore help scientists better understand how supermassive black holes, which can grow to masses billions of times that of the Sun, influence their environment and guide galactic evolution.
“There is an ongoing debate in the scientific community about how galaxies evolve. We find supermassive black holes at the centers of almost all Milky Way-sized galaxies, and an open question is how much influence they have compared to the effects of the star formation,” Goddard said. said astrophysicist and team leader Kimberly Weaver in a statement. “Studying nearby galaxies like NGC 4945, which we believe we are seeing in a transition period, helps us build better models of how stars and black holes produce galactic changes.”
An active galaxy where stars are born
While most galaxies have a supermassive black hole at their hearts, not all of these cosmic titans are accreting matter, nor is their gravitational influence churning up surrounding matter, generating the violent conditions necessary for AGN.
Galaxies like NGC 4945 that possess AGN, which can often outshine all the stars in the entire galaxy combined, are called “active galaxies.” But sometimes the thick donut- or “torus”-shaped dust at the center of these active galaxies is dense enough to obscure at least some of the AGN light from outside observers.
However, light is not the only emission from AGN at the heart of active galaxies; Matter that does not reach the black hole to be treated or “accumulated” can be channeled through magnetic fields towards the poles of the black hole. From here, these particles are accelerated to speeds close to the speed of light and are launched in the form of jets that can extend thousands of light years. Additionally, particles can escape from AGNs in active galaxies through powerful winds of gas and dust.
Possessing a supermassive AGN driven by a black hole is not the only thing that separates NGC 4945 from other quieter galaxies like the Milky Way. This nearby spiral galaxy is also classified as a “starburst galaxy,” indicating that it is undergoing an intense burst of star formation.
NGC 4945 is estimated to be forming stellar bodies at a rate of 18 Sun-like stars each year, three times faster than the rate of star formation in the Milky Way. This star birth is primarily centered in the heart of the galaxy and will only end when the raw material for star birth, the cold, dense gas clouds, is exhausted. This process is expected to take between 10 and 100 million years.
Spotting a misplaced cosmic fossil in NGC 4945
Observing NGC 4945 with the European Space Agency’s (ESA) XMM-Newton telescope, Weaver and his team detected a feature called the K-alpha iron line, which occurs when high-energy X-ray light from surrounding matter of the central supermassive black hole’s disk hits cold gas elsewhere in the galaxy.
The iron line is commonly seen in galaxies with an AGN, but this observation took the team by surprise because it was not as close to the central black hole as they expected and as existing theories suggest it should be.
The fact that NGC 4945 is seen edge-on from Earth’s point of view meant that NASA scientists were able to trace the iron line 32,000 light-years above the galactic plane and 16,000 years across the tilted galaxy.
“Chandra has mapped K-alpha iron in other galaxies. In this one, she helped us study individual bright X-ray sources in the cloud to help us rule out potential sources other than the black hole,” team member and postdoctoral researcher at Goddard . Jenna Cann said. “But NGC 4945’s line extends so far from its center that we needed XMM-Newton’s wide field of view to see it all.”
The team theorizes that the cause of this extraordinary feature is the particle jets that erupt from the supermassive black hole NGC 4945, 5 million years ago. They believe this jet was probably oriented so that it passed through the galaxy rather than escaping the galactic plane.
This eruption caused a super strong wind that still blows at NGC 4945 as we see it today, and could also have triggered the galaxy’s intense starburst period.
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The team will now continue observing NGC 4945 and look for other clues that show how the central black hole is influencing the evolution of the galaxy. They will also investigate whether X-rays from the central region could dissipate cold gas, eventually approaching intense star formation and quenching NGC 4945’s starburst phase.
“There is a body of evidence that black holes play important roles in some galaxies in determining their star formation histories and fates,” said team member and Goddard astrophysicist Edmund Hodges-Kluck. “We study many galaxies, like NGC 4945, because while the physics is virtually the same from black hole to black hole, the impact they have on their galaxies varies widely.”
“XMM-Newton helped us discover a galactic fossil we didn’t know how to look for, but it’s probably just the first of many.” Hodges-Kluck continued.
Weaver presented the team’s findings at the 243rd meeting of the American Astronomical Society in New Orleans, Louisiana, on Wednesday, January 11.
