- \n
- Black holes emit X-rays, which astronomers can detect with telescopes<\/strong>. Sometimes the frequency at which the X-rays are emitted can change.<\/li>\n
- Astronomers have just spotted X-ray flashes accelerating at a never-before-seen rate<\/strong>. They\u2019re coming from a supermassive black hole in another galaxy.<\/li>\n
- A white dwarf star might be causing the X-ray flashes<\/strong>. Scientists suggest the white dwarf is orbiting dangerously close to the black hole, increasing in speed as it gets closer.<\/li>\n<\/ul>\n
Unusual X-ray flashes from a distant black hole<\/h3>\n
Black holes \u2013 those powerhouses of nature from which not even light can escape \u2013 are known to emit X-rays. But in 2022, when observing flashes of X-rays from a supermassive black hole, researchers at the Massachusetts Institute of Technology (MIT) discovered something strange. The flashes were increasing in frequency at a never-seen-before rate. The researchers said on January 13, 2025, that the flashes have sped up from every 18 minutes to every seven minutes. And they outlined that they might originate from a white dwarf star speeding up as it gets closer and closer to the black hole\u2019s event horizon, that is, the boundary marking the limits of a black hole.<\/p>\n
The researchers presented their findings at the 245th meeting of the American Astronomical Society (AAS) in National Harbor, Maryland. Their peer-reviewed paper has been accepted for publication in Nature<\/em>. You can read a preprint version of the paper in arXiv.<\/p>\n
2025 EarthSky lunar calendar is available. A unique and beautiful poster-sized calendar with phases of the moon for every night of the year. Get yours today!<\/p>\n
Meet black hole 1ES 1927+654<\/h3>\n
1ES 1927+654 is a supermassive black hole that resides in a galaxy 100 million light-years away. It is about a million times more massive than our sun.<\/p>\n
Astronomers had observed interesting activity around this black hole before. In 2018, they saw that the corona \u2013 the extremely hot plasma around the black hole \u2013 suddenly disappeared. Then, a few months later, it re-appeared. Astronomers had never observed this phenomenon before. On top of that, the re-formed corona was the brightest X-ray-emitting object in the sky for a while. <\/p>\n
So, since 2018, this black hole has been one to watch. According to co-author Erin Kara:<\/p>\n
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It was still extremely bright, though it wasn\u2019t doing anything new for a couple years and was kind of gurgling along. But we felt we had to keep monitoring it because it was so beautiful. Then we noticed something that has never really been seen before.<\/p>\n<\/blockquote>\n
Accelerating black hole X-ray flashes<\/h3>\n
In 2022, the MIT astronomers observed something just as puzzling as the disappearing and re-appearing plasma. Using data from the European Space Agency\u2019s XMM-Newton space-based observatory, they monitored flashes of X-rays coming from the black hole. That itself isn\u2019t unexpected, as black holes are known to emit X-rays. But in this case, the flashes were accelerating<\/em>. They initially flashed every 18 minutes. But then they somehow sped up to flashing every seven minutes over the course of a couple years.<\/p>\n
Astronomers have seen black holes pulse with increasing frequency a few times before. But they\u2019ve never seen such a rapid increase. Co-author Megan Masterson at MIT said:<\/p>\n
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We\u2019ve never seen this dramatic variability in the rate at which it\u2019s flashing. This looked absolutely nothing like a normal black hole.<\/p>\n<\/blockquote>\n
The astronomers could tell from the flashes that whatever was producing them was probably quite close to the black hole. Kara explained:<\/p>\n
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Seeing something in X-rays is already telling you you\u2019re pretty close to the black hole. When you see variability on the timescale of minutes, that\u2019s close to the event horizon.<\/p>\n<\/blockquote>\n
Spinning white dwarf?<\/h3>\n
The researchers think the most likely explanation is a spinning white dwarf. A white dwarf is the hot core of a dead star. In this scenario, the white dwarf would be getting dangerously close to the black hole\u2019s event horizon. That\u2019s the boundary where, if an object gets any closer, the black hole will consume it and it will never be able to escape the black hole\u2019s immense gravitational pull. The white dwarf is probably within a few million miles of the event horizon. On a cosmic scale, that\u2019s very close indeed.<\/p>\n
The researchers said the white dwarf might be coming about as close to the boundary as possible without being sucked in forever. Masterson said:<\/p>\n
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This would be the closest thing that we know of around any black hole. This tells us that objects like white dwarfs may be able to live very close to an event horizon for a relatively extended period of time.<\/p>\n<\/blockquote>\n
![\"A](\"https:\/\/earthsky.org\/upl\/2020\/01\/supermassive-black-hole-artist-e1578744211743.jpg\")
Artist\u2019s concept showing the surroundings of a supermassive black hole typical of those found at the heart of many galaxies. A brilliant accretion disk of very hot infalling material and a dusty torus (donut-shaped ring) surrounds the black hole itself. High-speed jets of material are also often ejected at the black hole\u2019s poles that can extend huge distances into space. 1ES 1927+654, the source of the accelerating X-rays, is one such supermassive black hole. Image via ESO\/ Wikimedia Commons.<\/figcaption><\/figure>\n Gravitational waves<\/h3>\n
If a white dwarf really is responsible for the accelerating flashes, the researchers could further confirm that by detecting its gravitational waves. Those are basically \u201cripples\u201d in space-time caused by some of the most violent and energetic processes in the universe. However, this would require next-generation observatories such as NASA\u2019s Laser Interferometer Space Antenna (LISA), scheduled to launch in the mid-2030s. Kara said:<\/p>\n
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These new detectors are designed to detect oscillations on the scale of minutes, so this black hole system is in that sweet spot.<\/p>\n<\/blockquote>\n
The gravitational waves would also have the effect of dragging the white dwarf closer to the black hole. And the white dwarf would orbit the black hole increasingly faster the closer it got. Hence, the increase in the frequency of its X-rays.<\/p>\n
Could the white dwarf actually fall into the black hole?<\/h3>\n
The astronomers say it\u2019s unlikely that the white dwarf would fall into the black hole. As the white dwarf spirals closer, it sheds some of its outer layer. This offsets the movement toward the black hole just enough to prevent the white dwarf from actually crossing the event horizon boundary and falling into the black hole itself. In fact, it might even start to move farther away again. Kara explained:<\/p>\n
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Because white dwarfs are small and compact, they\u2019re very difficult to shred apart, so they can be very close to a black hole. If this scenario is correct, this white dwarf is right at the turn around point, and we may see it get further away.<\/p>\n<\/blockquote>\n
The discovery of the unusual X-ray flashes is a reminder that there is always something new to learn in science. As Masterson noted:<\/p>\n
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The one thing I\u2019ve learned with this source is to never stop looking at it because it will probably teach us something new. The next step is just to keep our eyes open.<\/p>\n<\/blockquote>\n
Bottom line: Astronomers at MIT have observed unusual black hole X-ray flashes that are accelerating in frequency. A white dwarf star near the black hole might be the cause.<\/p>\n
Source: Millihertz Oscillations Near the Innermost Orbit of a Supermassive Black Hole<\/p>\n
Via MIT<\/p>\n
Read more: Are primordial black holes hiding in plain sight?<\/p>\n
Read more: More evidence for black holes as the source of dark energy<\/p>\n
<\/div>\n
\n - Astronomers have just spotted X-ray flashes accelerating at a never-before-seen rate<\/strong>. They\u2019re coming from a supermassive black hole in another galaxy.<\/li>\n