NASA scientists have spotted a stunning cosmic fossil that was formed 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 Multi-Mirror Mission (XMM-Newton) space telescope with help from NASA’s Chandra X-ray Observatory to spot the X-rays that outline cold gas clouds in the relatively nearby area. spiral galaxy NGC 4945, 13 million light-years away in the constellation Centaurus (the Centaur).
The gas appears to have flowed through the galaxy as it shot 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, powering the bright galactic engine that is an active galactic nucleus (AGN). .
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This gas arranged 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 reach masses billions of times that of the Sun, influence their environment and drive 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 star formation,” says Goddard. astrophysicist and team leader Kimberly Weaver said in a statement. Studying nearby galaxies like NGC 4945, which we think we’re seeing in a transition period, helps us build better models of how stars and black holes drive galactic change.”
An active galaxy
Although most galaxies have a supermassive black hole at their heart, not all of these cosmic titans accumulate matter, nor do their gravitational influence create surrounding matter, creating the violent conditions necessary for AGN.
Galaxies like NGC 4945 that possess AGNs, which can often outshine every star 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 so dense that it can hide at least some of the AGN’s light from outside observers.
However, light is not the only emission from the AGNs at the heart of active galaxies; Matter that is not carried to the black hole for treatment, or ‘accreted’, can be channeled to the black hole’s poles by magnetic fields. From here, these particles are accelerated to speeds approaching that of light and are shot outward as jets that can extend for thousands of light years. Furthermore, particles can escape from the AGNs in active galaxies via powerful gas and dust winds.
Possessing a supermassive black hole-powered AGN isn’t the only thing that sets NGC 4945 apart from other, quieter galaxies like the Milky Way. This nearby spiral galaxy is also called a ‘starburst galaxy’, indicating that it is undergoing an intense burst of star formation.
It is estimated that NGC 4945 is forming stellar bodies at a rate of 18 Sun-like stars per year, three times faster than the star formation rate of the Milky Way. This star birth takes place mainly in the heart of the Milky Way and will only end when the raw material for star birth, cool and dense gas clouds, is exhausted. This process is expected to take between 10 million and 100 million years.
Spotting a lost cosmic fossil in NGC 4945
Looking at NGC 4945 with the European Space Agency’s (ESA) telescope XMM-Newton, Weaver and team discovered a feature called the iron K-alpha line, which forms when high-energy disk of the central supermassive black hole. hits cold gas elsewhere in the Milky Way.
The iron line is often seen in galaxies with an AGN, but this observation surprised the team 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 can be seen sideways from Earth’s vantage point meant that NASA scientists were able to track the iron line for 32,000 light-years above the galactic plane and 16,000 years across the tilted galaxy.
“Chandra has mapped iron K-alpha in other galaxies. In this galaxy, it helped us study individual bright X-ray sources in the cloud so we can rule out possible causes other than the black hole,” says team member and postdoctoral researcher at Goddard. said Jenna Cann. “But NGC 4945’s line extends so far from center that we needed XMM-Newton’s wide field of view to see everything.”
The team believes the cause of this extraordinary phenomenon is caused by particles that erupted from NGC 4945’s supermassive black hole 5 million years ago. They think this jet was probably oriented in such a way that it shot through the Milky Way instead of escaping the galactic plane.
This outburst created a super-strong wind that still blows in NGC 4945 as we see it today, and could also have caused the galaxy’s intense starburst period.
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The team will now continue to observe NGC 4945 and look for other clues showing how the central black hole influences the galaxy’s evolution. They will also investigate whether the X-rays from the central region can drive away cold gas, eventually bringing intense star formation close by and quenching NGC 4945’s starburst phase.
“There are some indications that black holes in some galaxies play an important role in determining their star formation history and fate,” said team member and Goddard astrophysicist Edmund Hodges-Kluck. ‘We study many galaxies, such as NGC 4945, because although the physics is much the same from black hole to black hole, the impact they have on their galaxies varies greatly.’
“XMM-Newton helped us discover a galactic fossil we didn’t know to look for, but it’s probably just the first of many.” Hodges-Kluck continued.
Weaver presented the team’s findings on Wednesday, January 11, at the 243rd meeting of the American Astronomical Society in New Orleans, Louisiana.