The analysis shows that the tiny black hole repeatedly pierces the gas disk of the larger black hole. At the heart of a distant galaxy, a supermassive black hole appears to have had a case of the hiccups. Astronomers from MIT, Italy, the Czech Republic and elsewhere have found that a previously quiescent black hole at the center of a galaxy about 800 million light-years away suddenly flared up, spewing plumes of gas every 8.5 days before. returning to a normal calm state.
Periodic hiccups are a new behavior not previously observed in black holes. Scientists believe the most likely explanation for the outbursts is a second, smaller black hole orbiting the central supermassive black hole and ejecting material from the gas disk of the larger black hole every 8.5 days.
Denial of black hole theories
The team's findings, which were published March 27 in the journal Science Advances , challenge the traditional picture of black hole accretion disks, which scientists thought were relatively uniform disks of gas orbiting a central black hole. The new results suggest that accretion disks may have more diverse contents, possibly containing other black holes and even entire stars.
"We thought we knew a lot about black holes, but this tells us that they can do a lot more," said study author Dheeraj "DJ" Pasham, a research fellow at MIT's Kavli Institute for Astrophysics and Space Studies. "We think there will be many more systems like this, and we just need to get more data to find them."
Computer simulation of an intermediate-mass black hole orbiting a supermassive black hole and triggering periodic plumes of gas that may explain observations
MIT study co-authors include postdoc Peter Kosek, graduate student Megan Masterson, associate professor Erin Cara, principal investigator Ronald Remillard, and former researcher Michael Fausn, as well as collaborators from multiple institutions, including Tor Vergata University of Rome, Astronomical Institute of the Czech Academy of Sciences, and Univ. Masaryk in the Czech Republic.
"Use it or lose it"
The team's findings came from automated detections using ASAS-SN (Automated All-Sky Survey for SuperNovae), a network of 20 robotic telescopes located at various locations in the Northern and Southern Hemispheres. Telescopes automatically scan the entire sky once a day for signs of supernovae and other transient phenomena.
In December 2020, researchers observed a flash of light in a galaxy about 800 million light-years away. This particular part of the sky was relatively quiet and dark until it was discovered by telescopes, when the galaxy suddenly became 1,000 times brighter. Pasham, who happened to see the detection reported in a community alert, decided to focus on the flare with NASA's NICER (The Neutron star Interior Composition Explorer) X-ray telescope aboard the International Space Station, which constantly monitors the sky. for X-ray flares that can signal the activity of neutron stars, black holes, and other extreme gravitational phenomena. The timing was fortuitous as it was nearing the end of the one-year period during which Pascham was allowed to point or "launch" the telescope.
"It was either use it or lose it, and that turned out to be the happiest outcome for me," he says.
He taught NICER to observe a distant galaxy that continues to flare. The outbreak lasted for about four months before it died down. During this time, NICER made daily measurements of the galaxy's high-frequency X-ray emission. When Paschem looked closely at the data, he noticed an interesting pattern in the four-month flare: subtle dips in a very narrow band of X-rays that appeared to appear every 8.5 days.
It seemed that the energy output in the galaxy periodically decreased every 8.5 days. The signal is similar to what astronomers see when an orbiting planet crosses its host star, briefly blocking the star's light. But no star can block the flash of an entire galaxy.
"I scratched my head as to what that meant, because this pattern doesn't fit everything we know about these systems," Pascham recalls.
Punch It
While searching for an explanation for the periodic failures, Pasham came across a recent paper by theoretical physicists from the Czech Republic. Theorists have separately concluded that, in theory, the galaxy's central supermassive black hole could contain a second, much smaller black hole. This smaller black hole may rotate at an angle to the accretion disk of its larger companion.
As the theorists assumed, the secondary hole would periodically pierce the disc of the primary black hole during its rotation. In the process, it would release a ball of gas like a bee flying through a cloud of pollen. Strong magnetic fields north and south of the black hole could throw the plume up and out of the claim Each time the smaller black hole pierces the disk, it ejects another plume in a regular, periodic fashion. If this plume happened to point in the direction of an observing telescope, it could observe the plume as a dip in the overall energy of the galaxy, briefly blocking the disk's light from time to time.
"I was very excited about this theory, and I immediately sent them an email saying, 'I think we're seeing exactly what your theory predicted,'" says Pasham.
He and Czech scientists teamed up to test the idea with simulations that included NICER's observations of the initial flare and regular 8.5-day declines. What they found supports this theory: the observed flare was likely the signal of a second, smaller black hole orbiting the central supermassive black hole and periodically puncturing its disk.
In particular, the team found that the galaxy was relatively quiet before its discovery in December 2020. The team estimates that the galaxy's central supermassive black hole has a mass of 50 million suns. Before the explosion, the black hole may have had a faint, diffuse accretion disk orbiting it, as a second, smaller black hole, between 100 and 10,000 solar masses, orbited in relative obscurity.
Researchers suspect that in December 2020, a third object—probably a nearby star—came too close to the system and was torn to pieces by the supermassive black hole's immense gravity, an event astronomers call a "tidal disruption event." The sudden influx of stellar material momentarily illuminated the black hole's accretion disk as debris from the star spiraled into the black hole. For four months, the black hole feasted on stellar debris, while the second black hole continued to spin. As it broke through the disk, it threw up a much larger plume than normal, which was ejected directly into NICER's sight.
The team ran numerous simulations to test for periodic drops. The most likely explanation for how they arrived is a new type of David and Goliath system—a tiny, intermediate-mass black hole orbiting a supermassive black hole.
"It's a different beast," Pasham says. "It doesn't match what we know about these systems. We see evidence that objects enter and pass through the disk at different angles, challenging the traditional picture of a simple disk of gas around black holes. We believe that there are a huge number of such systems."
“This is a brilliant example of how to use the debris of a collapsed star to illuminate the otherwise dark interior of the galactic core. It's like using a fluorescent dye to find a leak in a pipe," says Richard Saxton, an X-ray astronomer at the European Space Astronomy Center (ESAC) in Madrid, who was not involved in the study. "This result shows that very close binaries of supermassive black holes may be common in the cores of galaxies, which is a very exciting development for future gravitational wave detectors."
No comments:
Post a Comment