quasi periodic eruptions

At the center of the Milky Way, where the supermassive black hole Sagittarius A* churns gas clouds like a millstone, astronomers have caught an irregular pulse. Gamma-ray emission, the most energetic light in the universe, arrives not as a smooth wave but with a break, as if the Galaxy's heart beats with arrhythmia.

The night sky is full of rings and bubbles, but in the radio band they look different. In data from the Australian radio telescope ASKAP, a structure has surfaced that resembles two soap bubbles blown from the same straw.

A black hole paired with a star works like a pump: it pulls gas from its companion, swirls it into a glowing disk, and occasionally ejects some of that matter in two narrow jets. In 2021, the system 4U 1543-475 put on such a show.

Drop a pebble into a pond, and ripples spread across the water. Something similar happens when a black hole merges with another: it emits gravitational waves that resemble the fading ring of a bell.

A black hole is not an eternal vacuum cleaner. It slowly loses mass by emitting particles, much like a heated stone cooling as it radiates heat. This process, discovered by Stephen Hawking, is barely noticeable for large holes, but for tiny ones, with masses comparable to a mountain, it becomes a violent evaporation.

The cosmic detective story began with a quiet flash in the optical band. AT2019wzc slowly brightened and faded like a smoldering ember. But hidden inside was something more energetic — repeating soft X-ray bursts that astronomers call quasi-periodic eruptions. These eruptions last minutes to hours and repeat every few hours or days.

In the distant Cigar Galaxy, there is an unusual beacon. It doesn't shine in the usual sense: its rays are born in a scorching cloud around a black hole that is devouring matter from a companion star. Such objects are called ultraluminous X-ray sources. Their X-ray brilliance is so intense that it outshines entire galaxies. This cloud, the corona, is like a boiling cauldron.

A black hole is not silent. When perturbed, it rings like a bell, and that ring is its quasinormal modes — damped oscillations. Physicists delved into the world of charged black holes in anti-de Sitter space (a universe with negative curvature, like a saddle).

A black hole is not just an abyss. It is a seething cauldron whose temperature rises as it evaporates. The authors of the study found that when the heat reaches a critical threshold, the hole seems to boil. It emits superheavy particles — the very ones that exist on a scale where any theory of gravity collapses.

A black hole is not an absolutely black bag. In 1974, Stephen Hawking showed that it glows — faintly, but continuously. This radiation is born not inside, but outside, right at the boundary from which even light cannot escape. A new study sharpens the picture.

295 000 meters per second. Not even particles in solar coronal ejecta move that fast. But at the center of the galaxy cluster H1821+643, hot gas does exactly that. The quasar at its heart takes a breath, and its breath stirs everything around for 60 thousand light-years.

A branch falls into a whirlpool. It gets spun and broken, but sometimes a powerful fountain of water bursts from the center. Similarly, a black hole tears apart a passing star, and occasionally a blinding plasma jet, a jet, shoots into space.

Space is full of invisible waves — ripples in the fabric of spacetime left behind by cataclysms like black hole mergers. An ordinary black hole swallows everything without a trace. But there are hypothetical exotic objects — ultradense clumps of matter without an event horizon (a surface from which not even light can escape).

Ten billion years ago, the universe was speckled with strange crimson sparks. The JWST spotted them in images at distant redshifts — compact sources blazing like entire galaxies yet no larger than a tiny central region. Astronomers nicknamed them “little red dots.” Their nature long defied explanation.

The Sun is constantly struck by blows — magnetic reconnection in the plasma releases energy, making the corona flare up. After each such blow, magnetohydrodynamic waves linger in the plasma loops, like the fading ring of a bell.

The cosmos is full of screams we can't hear. Every time a black hole tears a star apart, a blinding flash is born, and often — a narrow relativistic jet, shooting out thousands of light-years. But if that searchlight is aimed away from Earth, we see only a faint afterglow — a radio echo arriving with a delay.

A black hole merger is not a silent impact. The newborn hole quivers and decays, emitting gravitational waves — ripples in space itself. This signal is called the 'ringdown,' and it resembles the fading chime of a bell: it has a fundamental tone and several overtones.

Crystals fascinate us with their perfect spatial order: atoms frozen at lattice points, like beads on an invisible string. But what if the same symmetry unfolds in time? Time crystals are systems that, without any external cue, start repeating their states cyclically — clocks wound by nature itself. Inside this tireless rhythm, disorder seems to have no place.

Deep space, galactic center. A supermassive black hole is surrounded by a scorching disk of gas and dust. And then, through this fiery veil, a star shoots by every few hours — like an arrow loosed from the bow of gravity. Each passage triggers a dazzling X-ray flare that for a moment outshines the entire galactic nucleus.

The NICER X-ray telescope has become a precise stethoscope for astrophysicists. In 2025, it was 'listening to' the black hole in the binary system 4U 1630−47—a compact object born from the core collapse of a massive star (the stability limit for white dwarfs was…

A black hole is not just a vacuum cleaner. It glows faintly, emitting particles — this idea was proposed by Jacob Bekenstein, who connected the hole's temperature to its degree of disorder. Detecting such radiation in space is incredibly difficult.

A black hole with an electric charge is like a vacuum cleaner that not only sucks in everything around it but can also hold light particles in orbit. These particles form a kind of fuzzy cloud around the hole — physicists call it a quasi-bound state.

A black hole is not a dead object. After a disturbance, such as merging with another hole, it rings like a bell. This ring is not just a sound but a complex set of damped oscillations called quasinormal modes. Their frequency and damping rate depend on the hole itself: its mass, charge, and spin.

In the centers of distant galaxies, X-ray 'beacons' sometimes light up. They don't flash randomly but on a strict schedule: every few hours or days. These bursts are called quasi-periodic eruptions (repeating at nearly regular intervals).

A black hole is not a frozen void, but a living magnetic engine. Its 'heart'—the accretion disk, pulsates: inhale, matter spirals into the funnel, exhale — magnetic reconnection tears the field lines, and plasma shoots away from the horizon.

In the summer of 2021, comet 7P/Pons-Winnecke put on quite a show. A network of telescopes, the Las Cumbres Observatory, tracked it for nearly three months and counted eight sudden outbursts.

In the scorching plasma of the infant Universe, right after inflation, conceived by Alan Guth, the kinetic dominance epoch reigned.

A pot of porridge boiling over a high flame: bubbles carry grains from the bottom to the surface. A similar mechanism works on a neutron star. As it accumulates hydrogen and helium from a companion star, it occasionally triggers a powerful nuclear explosion — an X-ray burst.

A black hole rings like a bell when something massive falls into it. This ring is gravitational waves, and its overtones tell us about the shape of the horizon.

Gravitational waves from a tiny body falling into a black hole work like an X-ray image. Only instead of a bone, they illuminate the curved spacetime itself.

In the accretion disks that gird the nuclei of active galaxies (quasars, discovered by Maarten Schmidt way back in the 1960s) a river of incandescent gas and dust churns. In its backwaters, where turbulent flows subside, against all odds, planets are born.

A radio telescope is not just an antenna, but a computing machine that builds an image from millions of equations. This mathematical prism is as fragile as glass: one wrong digit in the calibration, and the real sky splits, spawning phantom sources.

In the constellation Scorpius, 3,000 light-years from Earth, a dead star steals matter from a living one. A white dwarf in the system IGR J17014-4306 — a superdense carbon-oxygen ball with the mass of the Sun but the size of Earth — siphons hydrogen from a normal companion star.

Heir to the ideas of Edwin Hubble, the James Webb Space Telescope has peered back to an era when the expansion of the universe was still picking up speed. At redshifts z>4, it spotted bizarre objects—"Little Red Dots" (LRDs).

In 2022, astronomers began discovering strange cosmic beacons — long-period radio transients. Unlike fast pulsars, discovered by Jocelyn Bell Burnell in 1967, these objects flared with periods of tens of minutes and hours.

In the centers of galaxies, where supermassive black holes lie dormant surrounded by stellar swarms, lights of monstrous power sometimes flare up — tidal disruption events. But some of these events behave oddly: they repeat again and again, and each new ignition is dimmer than the last.

A light beam approaches a black hole not head-on, but at a glancing angle. If the angle is just right, the light neither falls in nor escapes: it starts looping around, like a figure skater circling the rim of a funnel. This narrow track is the photon ring. It acts like a lens, repeatedly reflecting the image of everything that falls into the hole.

Just a few hundred million years after the Big Bang, in the ocean of invisible dark matter, giant black holes were already taking shape. They were born from the matter itself — without any help from stars. This mechanism, based on the equations of Lemaître, explains their early appearance.

A black hole is like a whirlpool in the ocean: anything that falls in disappears forever. But if the whirlpool spins and carries a slight electric charge, and invisible axion particles (dark matter candidates) are buzzing around it, its surface stops being smooth.

The city has long been asleep: not a single lit window, not a single new house. Only in the very center, in one lone building, someone forgot to turn off a spotlight. That's what a galaxy looks like when stars are no longer born, yet its central black hole still shines.