A plasma jet and X-ray flashes arising from a supermassive black hole

Unprecedented features at brink of active black hole.

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International astronomers discovered new features in a supermassive black hole using information from NASA missions and other sources. They saw a plasma jet traveling at nearly one-third the speed of light and rapid X-ray changes from close to the black hole.

Galaxy 1ES 1927+654, located about 270 million light-years away in the constellation Draco, has a central black hole about 1.4 million times the mass of the Sun.

In 2018, this black hole started showing significant changes, including optical, ultraviolet, and X-ray light bursts. Researchers have been closely monitoring it ever since.

After the outburst, the black hole calmed down for almost a year. But by April 2023, a team led by Sibasish Laha at UMBC and NASA’s Goddard Space Flight Center noticed a steady increase in low-energy X-rays using NASA’s Neil Gehrels Swift Observatory and NICER telescope on the International Space Station. This monitoring includes NASA’s NuSTAR and ESA’s XMM-Newton mission.

The X-ray increase led the team to make new radio observations, revealing a strong and unusual radio flare. They then used the NRAO’s VLBA (Very Long Baseline Array) to see features that are less than a light-year across the galaxy 1ES 1927+654.

Active galaxy 1ES 1927+654
Active galaxy 1ES 1927+654, circled, has exhibited extraordinary changes since 2018, when a major outburst occurred in visible, ultraviolet, and X-ray light. The galaxy harbors a central black hole weighing about 1.4 million solar masses and is located 270 million light-years away. Pan-STARRS

Radio data from early 2024 showed jets of ionized gas, or plasma, coming from both sides of the black hole, stretching about half a light-year. Astronomers have wondered why only some supermassive black holes create these powerful jets, and these new observations might help answer that question.

Eileen Meyer, an associate professor at UMBC, said, “The launch of a black hole jet has never been observed before in real-time. We think the outflow began earlier, when the X-rays increased before the radio flare, and the jet was screened from our view by hot gas until it broke out early last year.”

Based on the observation from the XMM-Newton, astronomers found that the black hole exhibited extremely rapid X-ray variations between July 2022 and March 2024. During this time, the X-ray brightness increased and decreased by 10% every few minutes. These changes, known as millihertz quasiperiodic oscillations, are rare around supermassive black holes and have only been seen in a few systems.

One possible explanation is that an object orbits within the black hole’s accretion disk, causing the X-ray brightness to rise and fall with each orbit.

If an orbiting object caused the fluctuations, its period would get shorter as it moved closer to the black hole’s event horizon (the point of no return). Orbiting objects create ripples in space-time called gravitational waves, which reduce orbital energy and pull the object closer to the black hole, speeding it up and shortening its orbit.

Over two years, the fluctuation period decreased from 18 minutes to just 7 minutes — the first time this has been measured around a supermassive black hole. If this were an orbiting object, it would be moving at half the speed of light. Then, surprisingly, the fluctuation period stabilized.

Masterson was surprised at first but realized that as the object approached the black hole, its strong gravity could strip matter from the companion. This mass loss could counteract the energy removed by gravitational waves, stopping the companion’s inward movement.

What could the companion be? A small black hole would fall straight in, and the black hole’s tidal forces would tear apart a normal star. However, the team found that a low-mass white dwarf, a stellar remnant about the size of Earth, could stay intact near the black hole’s event horizon while losing some of its matter.

Journal Reference:

  1. Megan Masterson, Erin Kara, Christos Panagiotou et al. Millihertz Oscillations Near the Innermost Orbit of a Supermassive Black Hole. The Astrophysical Journal Letters. DOI: 10.48550/arXiv.2501.01581
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