Do Black Holes Have Hidden Hair? Scientists Find A New Way To Check
After a black hole is disturbed, it emits gravitational waves that fade over time, a signal called ringdown. These waves may reveal hidden matter nearby. Researchers found that this hidden matter would alter the frequency and fade-out speed by different amounts. This would change the waves in a distinctive way and give scientists a new approach to test Einstein's theory of general relativity.
CREDIT: Ariadna Uxue Palomino Ylla, Nagoya University
September 7, 2026
By Eurasia Review
Key Takeaways:
September 7, 2026
By Eurasia Review
Key Takeaways:
After two black holes merge, the new hole “rings” and sheds gravitational waves—the ringdown. For the simplest Kerr black hole that depends only on mass and spin. Extra matter or new physics (“hair”) can change that signal.
A Nagoya University team (first author Ariadna Uxue Palomino Ylla), in the Journal of Cosmology and Astroparticle Physics, shows hair does not shift frequency and damping the same way. The mismatch depends on how much hidden matter there is and how its pressure sits around the hole—and, for spinning holes, on whether the waves co-rotate or counter-rotate with the spin.
Method: use the known link between near-horizon light orbits and ringdown, add a little extra matter to standard models, and compute the change. The aim is a shared template for future LIGO-class data—to tell a “hairy” hole from a bald one, not a detection claim today.
When two black holes crash together and merge, the newly formed black hole rings like a bell, sending out gravitational waves with specific frequencies that fade over time. This brief, fading pattern of waves is called ringdown, and it may hold secrets about what is hiding around black holes.
Under Einstein’s basic rules for the simplest kind of black hole, ringdown waves depend only on two things: a black hole’s mass and how fast it spins. But what if black holes have hidden matter around them? If this were true, this matter would also affect characteristics of the ringdown waves. As a result, ringdown may hold information about hidden matter surrounding the black hole. In theoretical physics, this extra structure is often called “black hole hair.”
A team led by researchers from Nagoya University in Japan has found a way to check for hair using changes in ringdown waves. They found that hidden matter does not affect these waves uniformly; the frequency and fade-out speed of the waves respond differently. This difference may show us if hidden matter is present, and how its pressure is arranged around a black hole.
For spinning black holes, hidden matter affects ringdown differently, depending on whether the waves move with or against the black hole’s spin. Published in the Journal of Cosmology and Astroparticle Physics, the study tells us what pattern in the gravitational wave signal would be a clue that hidden hair is present and may help future observations tell a hairy black hole apart from an ordinary one.
If hairy black holes exist
Scientists continue testing whether Einstein’s theory of general relativity perfectly describes black holes and what deviations may exist.
Finding signs of black hole hair is difficult because different kinds of extra matter or new physics can change the ringdown in different ways. This study gives researchers a clearer idea of what patterns to look for in future ringdown data.
“Black hole hair may represent matter surrounding the black hole, or deviations from the simplest kind of black hole predicted by general relativity. Because these may slightly change the ringdown signal, detecting or ruling out these changes could give us a new way to test gravity in this extreme region,” said first author Ariadna Uxue Palomino Ylla, a PhD student from Nagoya University’s Graduate School of Science.
A black hole distorts space time so severely that it bends the path of light and gravitational waves. If there is hidden matter or new physics affecting gravity, the effects would be most pronounced exactly where gravity is strongest. This makes black holes the best place to find out if hidden matter or unknown physics might be present.
To check for hair, the team relied on a known link. The way light would orbit near a black hole corresponds to the way its ringdown waves behave, so scientists can calculate one from the other. They added a small amount of hidden matter to standard black hole models and used Einstein’s equations to calculate how that matter changes the ringdown’s frequency and fade-out speed.
The researchers tested this approach on three well-known theoretical black holes. They also extended it to spinning black holes and studied light that orbits with the spin and light that orbits against it.
Hair affects frequency and fading speed differently
A key finding is that the frequency and fade-out speed of ringdown waves do not change in the same way. The difference between them depends on how much hidden matter is present and how its pressure is arranged around the black hole.
“The ringdown waves may not only show that something extra is affecting the black hole; the way the signal changes could also give us clues about what this hidden matter is actually like,” said Palomino Ylla.
The researchers included spinning black holes in their analysis. Rotation makes calculations more complex because light circling with the black hole’s spin would behave differently from light circling against it. Hidden matter would also change the ringdown’s frequency and fade-out speed differently, depending on the spin direction. The exact pattern depends on the type of hidden matter involved.
Instead of studying each possible type of black hole hair from scratch, the new method gives researchers a common way to predict how extra matter or new physics could change a black hole’s ringdown. While the results are early estimates, this method helps scientists know what to look for if they ever spot something strange in a real black hole’s signal. In the future, this approach may help researchers use these waves to learn about a black hole’s size, spin, and any black hole hair nearby.
Comets May Have Transported Water To A Young Planetary System
September 3, 2026
By Eurasia Review
Key Takeaways:
2018 data show sodium gas moving at several km/s relative to the star and appearing and vanishing over nights—consistent with comets heating and sublimating as they pass. The team calls this the youngest system with proposed exocomet activity, and the first such case around a relatively cool, Sun-like star.
Orbit models suggest the gas giants can fling outer icy bodies inward, a possible water-delivery route like one proposed for early Earth. Chile’s coming Extremely Large Telescope may reveal more planets and how volatiles move.
Astronomers at Lund University in Sweden have found evidence of exocomets – comets in other solar systems – orbiting a young star similar to our Sun. The observations point to a possible mechanism for how water might be transported from the cold outer regions of the planetary system to regions where planets form.
The PDS 70 planetary system is just over five million years old and lies around 370 light-years from Earth. The system has at least two gas giants and orbits a star that is slightly cooler than the Sun. Water vapour was detected near the star as early as 2023. Researchers in Lund have now shown that variations in sodium gas in front of the star may be a sign of comets passing through the inner parts of the system.
“Our study suggests that comets may be responsible for transporting water to the inner parts of the planetary system, where planets can form, in the same way as in the early Solar System,” says Aline Novais, an astronomy researcher at Lund University.
The researchers have analysed observations from 2018 and detected sodium gas moving at several kilometres per second relative to the star. The gas appears and disappears over the course of several nights – a pattern consistent with what one would expect when comets pass in front of a star. When a comet approaches its star, it heats up and the ice on its surface turns directly into gas – a process known as sublimation. The gas can then leave a measurable imprint in the star’s light.
“This is the first time we have seen evidence of exocomets orbiting a star that is relatively cool, much like our Sun. Furthermore, this system is the youngest in which exocomet activity has been proposed,” says Aline Novais.
The researchers have also simulated the comets’ orbits. The results show that objects far out in the planetary system can be affected by the gravitational pull of the gas giants and flung towards the star. This is particularly interesting because comets form in the cold outer regions of the planetary system, where water may exist as ice. If they are then channelled inwards, they can transport water and other volatile substances to the region where planets form.
“It is reminiscent of a possible process in the early Solar System, in which comets may have helped to deliver water to the young Earth,” says Alexandra Stockwell Murphy, an astronomer at Lund University.
Where the Earth’s water originally came from remains an open question. Water-rich asteroids and comets are two possible sources. PDS 70 gives researchers the opportunity to study a similar process whilst a planetary system is still in its early stages of development.
“And when the Extremely Large Telescope, which is currently being built in Chile, becomes operational in the coming years, we will be able to find out whether there are any further planets in the system and thus gain an even clearer picture of how water and other building blocks of planets are transported,” concludes Jens Hoeijmakers, an astronomy researcher at Lund University.
September 3, 2026
By Eurasia Review
Key Takeaways:
Lund astronomers report signs of exocomets around PDS 70, a ~5-million-year-old, slightly cooler Sun-like star about 370 light-years away that already has at least two gas giants and inner-system water vapour (detected 2023).
2018 data show sodium gas moving at several km/s relative to the star and appearing and vanishing over nights—consistent with comets heating and sublimating as they pass. The team calls this the youngest system with proposed exocomet activity, and the first such case around a relatively cool, Sun-like star.
Orbit models suggest the gas giants can fling outer icy bodies inward, a possible water-delivery route like one proposed for early Earth. Chile’s coming Extremely Large Telescope may reveal more planets and how volatiles move.
Astronomers at Lund University in Sweden have found evidence of exocomets – comets in other solar systems – orbiting a young star similar to our Sun. The observations point to a possible mechanism for how water might be transported from the cold outer regions of the planetary system to regions where planets form.
The PDS 70 planetary system is just over five million years old and lies around 370 light-years from Earth. The system has at least two gas giants and orbits a star that is slightly cooler than the Sun. Water vapour was detected near the star as early as 2023. Researchers in Lund have now shown that variations in sodium gas in front of the star may be a sign of comets passing through the inner parts of the system.
“Our study suggests that comets may be responsible for transporting water to the inner parts of the planetary system, where planets can form, in the same way as in the early Solar System,” says Aline Novais, an astronomy researcher at Lund University.
The researchers have analysed observations from 2018 and detected sodium gas moving at several kilometres per second relative to the star. The gas appears and disappears over the course of several nights – a pattern consistent with what one would expect when comets pass in front of a star. When a comet approaches its star, it heats up and the ice on its surface turns directly into gas – a process known as sublimation. The gas can then leave a measurable imprint in the star’s light.
“This is the first time we have seen evidence of exocomets orbiting a star that is relatively cool, much like our Sun. Furthermore, this system is the youngest in which exocomet activity has been proposed,” says Aline Novais.
The researchers have also simulated the comets’ orbits. The results show that objects far out in the planetary system can be affected by the gravitational pull of the gas giants and flung towards the star. This is particularly interesting because comets form in the cold outer regions of the planetary system, where water may exist as ice. If they are then channelled inwards, they can transport water and other volatile substances to the region where planets form.
“It is reminiscent of a possible process in the early Solar System, in which comets may have helped to deliver water to the young Earth,” says Alexandra Stockwell Murphy, an astronomer at Lund University.
Where the Earth’s water originally came from remains an open question. Water-rich asteroids and comets are two possible sources. PDS 70 gives researchers the opportunity to study a similar process whilst a planetary system is still in its early stages of development.
“And when the Extremely Large Telescope, which is currently being built in Chile, becomes operational in the coming years, we will be able to find out whether there are any further planets in the system and thus gain an even clearer picture of how water and other building blocks of planets are transported,” concludes Jens Hoeijmakers, an astronomy researcher at Lund University.
No comments:
Post a Comment