A faltering supermassive black hole has alerted astronomers to a whole new type of black hole behavior.
In 2020, a previously silent black hole suddenly erupted at the heart of a galaxy about 800 million light-years from Earth, and with a mass equivalent to 50 million suns, brightening the material around it by a factor of 1,000.
A team of researchers believe these periodic outbursts are caused by a second, smaller black hole colliding with a disk of gas and dust, called an “accretion disk,” that surrounds the supermassive black hole, causing it to repeatedly “hiccup” matter.
The findings challenge the conventional view of how black hole accretion disks function. Previously, scientists believed they were uniform disks of gas and dust rotating around a central black hole. However, the new results suggest that some accretion disks may contain exotic components, such as stars and even smaller secondary black holes.
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“This is a different beast. It doesn’t match anything we know about these systems. We thought we knew a lot about black holes, but this tells us there are many more things they can do,” said team member Dheeraj. “DJ” Pasham, a scientist at the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology, said in a statement.
“We think there will be many more systems like this, and we just need more data to find them,” Pasham added.
Hunting for a ‘different beast’ black hole system
The team was initially tipped off to this glitching black hole while examining data from the All Sky Automated Survey for SuperNovae (ASAS-SN), a network of twenty telescopes around the world that surveys the entire sky above Earth once a day. scan earth.
As ASAS-SN automatically scanned the sky in December 2020, the robotic telescopes spotted a burst of light in a previously quiet patch of sky containing a galaxy about 800 million light-years away. Pasham chased this flare using the Neutron Star Interior Composition Explorer (NICER), a NASA X-ray telescope on the International Space Station (ISS).
Pasham only had a short time to use the ISS-based telescope, which is used to search the cosmos for X-ray bursts erupting from neutron stars, black holes and other extreme gravitational phenomena. That meant he had to act quickly and act quickly. happy.
“It was either use it or lose it, and it turned out to be my luckiest break,” Pasham said.
The researcher observed that this galaxy continued to flare up, with the outburst lasting about four months. In NICER observations of this flare, Pasham discovered a curious pattern of subtle dips in X-rays and the energy of the eruption every 8.5 days. The signal almost resembled the light dip caused when an exoplanet crosses or ‘crosses’ the side of its star, briefly blocking starlight.
“I was wondering what this means, because this pattern doesn’t fit what we know about these systems,” Pasham added.
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Pasham’s confusion was cleared up when he found research suggesting that a supermassive black hole at the heart of a galaxy orbiting Earth could be orbited by an intermediate-mass black hole, a black hole with a mass between 100 and 10,000 times that of the sun.
This smaller black hole could orbit its larger counterpart in such a way that it darts in and out of the supermassive black hole’s accretion disk. As it pushes through this gas and dust, the smaller black hole emits a plume of gas. Each dive would create a new plume, hence the periodic pattern of these ‘hiccups’.
When these plumes are directed toward Earth, they can be observed as a sudden drop in the energy of the affected system, as the light from the accretion disk is periodically obscured, much like starlight does from a passing exoplanet.
“I was super excited about this theory and I immediately emailed them to say, ‘I think we’re observing exactly what your theory predicted,'” Pasham added.
This prompted the authors of that first study to create simulations that incorporated NICER data. These confirmed that the observed 8.5-day signal is likely the result of a small black hole piercing the accretion disk of its larger supermassive black hole companion.
What caused the supermassive black hole to hiccup? Too much spaghetti
However, this still doesn’t explain why the supermassive black hole suddenly erupted – only why this burst periodically weakens. The team believes that this black hole came to life because a star recently came too close to its outer boundary, the ‘event horizon’.
The supermassive black hole’s enormous gravitational influence would generate enormous tidal forces on approaching stars, stretching them vertically and crushing them horizontally, in a process called “spaghettification.” This would cause the star to burst apart during a tidal disruption, causing a powerful burst of light and a sudden influx of matter that brightened the accretion disk.
In the case of the newly observed galaxy, the added material apparently fueled the supermassive black hole for four months, the duration of the outburst, and also meant that when the smaller secondary black hole crashed through this material, it released a larger plume of gas to fly. gasoline than normal.
“We see evidence that objects enter and pass through the disk at different angles, challenging the traditional view of a simple gaseous disk around black holes,” Pasham said. “We think there’s a huge population of these systems out there.”
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Richard Saxton is an X-ray astronomer at the European Space Astronomy Center in Madrid and was not involved in the research. He said the new findings, and the technique used to achieve them, could ultimately help astronomers better understand supermassive black holes and the exotic environments they live in.
“This result shows that very close supermassive black hole binaries could be common in galactic nuclei, which is a very exciting development for future gravitational wave detectors,” Saxton said in a statement. “This is a brilliant example of how you can use the debris of a disrupted star to illuminate the interior of a galactic core that would otherwise remain dark. It is similar to using fluorescent dye to find a leak in a pipe.”
The team’s research was published Wednesday (March 27) in the journal Science Advances.