In 2018, astronomers discovered that the corona of 1ES 1927+654, an actively accreting black hole with 1.4 million solar masses located in a galaxy some 270 million light-years away, suddenly disappeared and reassembled several months later. I observed that. The short but dramatic outage was the first of its kind in black hole astronomy. Now, astronomers using ESA's XMM-Newton Observatory have captured the same black hole exhibiting even more unprecedented behavior. They detected X-ray flashes from 1ES 1927+654 at a steadily increasing clip. Over a two-year period, the frequency of millihertz vibration flashes increased from every 18 minutes to every 7 minutes. This dramatic speed-up of X-rays has never been observed from a black hole before.
In this artist's concept, material is stripped from a white dwarf (bottom right sphere) orbiting within the innermost accretion disk surrounding the supermassive black hole of 1ES 1927+654. Image credit: NASA/Aurore Simonnet, Sonoma State University.
Black holes are a prediction of Albert Einstein's theory of general relativity. They are gravitational monsters that trap any matter or energy that crosses their “surface,” a region of spacetime known as the event horizon.
In its final descent into the black hole, a process known as accretion, the doomed material forms a disk around the black hole. The gas in the accretion disk heats up and emits primarily ultraviolet (UV) light.
The ultraviolet light interacts with the cloud of electrically charged gas or plasma that surrounds the black hole and accretion disk. This cloud is known as the corona, and the interaction energizes the ultraviolet light and amplifies it into X-rays, which can be captured by XMM Newton.
XMM-Newton has been observing 1ES 1927+654 since 2011. Back then, everything was very normal.
But things changed in 2018. As the X-ray corona disappeared, the black hole erupted in a massive explosion that seemed to disrupt its surroundings.
The coronavirus gradually returned, and by early 2021, it seemed like normal conditions had returned.
However, in July 2022, XMM Newton began observing its X-ray output fluctuating at a level of about 10% on timescales of 400 to 1,000 seconds.
This type of fluctuation, called quasi-periodic oscillations (QPO), is notoriously difficult to detect in supermassive black holes.
“This was the first sign that something strange was going on,” said Dr. Megan Masterson. Student at MIT.
The oscillations could suggest that a massive object, such as a star, is embedded in the accretion disk and rapidly orbiting the black hole on its way to being swallowed.
As an object approaches a black hole, the time it takes to orbit decreases and the frequency of its oscillations increases.
Calculations revealed that the orbiting object was probably the remains of a star known as a white dwarf, had about 0.1 times the mass of the Sun, and was moving at an astonishing speed.
It was completing one orbit of the central monster, covering a distance of about 100 million km, about every 18 minutes. Then things got even weirder.
Over nearly two years, XMM Newton showed an increase in the strength and frequency of the vibrations, but not as much as the researchers expected.
They assumed that an object's orbital energy is being emitted as gravitational waves, as prescribed by the theory of general relativity.
To test this idea, they calculated when the object crossed the event horizon, disappeared from view, and stopped oscillating. It turns out to be January 4, 2024.
“Never in my career have I been able to predict anything so accurately,” says Dr. Erin Kara of MIT.
In March 2024, XMM Newton observed it again and the oscillations were still present.
The object was currently traveling at about half the speed of light, completing an orbit every seven minutes.
Whatever was inside the accretion disk, it stubbornly refused to be swallowed up by the black hole.
Either something more than gravitational waves is at play, or the entire hypothesis needs to be changed.
Astronomers also considered other possibilities for the origin of the vibrations.
Remembering that the X-ray corona disappeared in 2018, they wondered if this cloud itself was vibrating.
The problem is that there is no established theory to explain such behavior, so there is no clear path to take this idea further, so they go back to the original model and realize there is a way to fix it. I did.
“If the black hole has a white dwarf companion, the gravitational waves produced by the black hole could be detected by LISA, an ESA mission scheduled to launch within the next 10 years in partnership with NASA.” said Masterson.
team's paper will appear in journal nature.
_____
Megan Masterson others. 2025. Millihertz oscillations near the innermost orbit of a supermassive black hole. naturein press. arXiv: 2501.01581
Source: www.sci.news
