transient

In active galactic nuclei, supermassive black holes are surrounded by a dense ring of dust that acts like a curtain: it hides everything happening at the center. If a star ventures too close to the black hole, tidal forces tear it apart, and the resulting flare is usually visible in optical and X-ray light.

In the early hours of March 4, 2020, the TESS telescope, normally on the hunt for planets around other stars, spotted something odd in a far-off galaxy. The light from an object called AT 2020afjz flared and faded in just a couple of hours, quicker than it takes a cup of coffee to cool.

In the early hours of March 4, 2020, the TESS telescope, normally on the hunt for planets around other stars, spotted something odd in a far-off galaxy. The light from an object called AT 2020afjz flared and faded in just a couple of hours, quicker than it takes a cup of coffee to cool.

A stone thrown into water quickly loses speed. A meteor entering the atmosphere should behave the same way: air slows it down, and friction burns up its material. But cameras of the Global Fireball Observatory network have captured hundreds of bright fireballs over ten years that streak across the sky with almost no deceleration.

Buried in Antarctic ice, there's a detector the size of a cubic kilometer. It doesn't catch light but ghostly particles — neutrinos. Yet sometimes, a different beast might flash through: a pair of muons born together and flying apart in a wide fan. No known particle of ordinary matter can paint that pattern.

In a binary star system, one star pulls matter from its companion. Over centuries, this material settles onto the surface of a neutron star — the ultra-dense remnant of a dead star. This process, called accretion, usually proceeds smoothly. Gravity behaves as general relativity predicts, without surprises.

The universe is a vast, dark ocean. We see only the glowing foam on its surface — stars and galaxies. But hidden in the depths are two invisible forces: dark matter, which with its gravity keeps galaxies from flying apart, and dark energy, which, on the contrary, pushes space itself apart, making the universe expand faster and faster.

The hunter of ancient light, the James Webb Telescope, aimed its mirrors at a tiny patch of sky and caught a strange beacon. The object, with the working name beacon_1420-$$5253_{4770}$$, flashed and faded. At first, it was logged as a candidate for the most distant galaxy, as if we were seeing it just 300 million years after the big bang.

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.

Long-period radio transients (LPTs) are a mysterious class discovered only recently. Their pulses last minutes or hours, and their nature was completely unknown. ASKAP J1745-5051, caught by the Australian telescope ASKAP, became the first to get a full explanation.

Moments before totality, swift shadow bands glide across the ground, like ripples from pebbles tossed into water. For centuries, this phenomenon baffled scientists. It turns out the key is that light is a wave. The Sun isn't a pinpoint lamp but a vast disk. When the Moon nearly covers it, a thin glowing crescent remains.

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.

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.

Two stars circle each other like dancers in a slow waltz. This dance is not eternal: the partners gradually draw closer until they collide and merge into a single entity. At that very moment, a red nova is born — a flash that lights up the sky for a few weeks, then slowly fades, enveloped in a dense cloud of dust.

Two lamps in a shop window: one glows with a cool, bluish light, the other a bit warmer and yellower. That's roughly how the two types of supernovae, Ib and Ic, look when astronomers view them through a telescope.

In a distant galaxy, at a distance that light takes 11 billion years to cross, something flashed. The Einstein Probe X-ray telescope caught a brief, needle-prick-like burst: it lasted only a few dozen seconds.

To spot a dim star above a brightly lit city, astronomers subtract one image from another — removing the glare of streetlights. They do the same with living neurons: their faint flashes drown in noise, but if you subtract everything unchanging, only they remain.

For twelve years, astronomers at the LPA radio telescope in Pushchino have been listening to the same patch of sky — the direction of the galaxy 3C 33. In that time, they caught just six short radio signals, each lasting from one to four minutes.

Every day, particles with colossal energy enter Earth's atmosphere, like unsigned letters. Their source long remained a mystery. New research shows: these 'visitors' point to nearby galaxies, where from time to time catastrophes occur — collisions of neutron stars, ultra-dense spheres the size of a city but with the mass of the Sun.

For seven hours straight, a space gamma-ray telescope registered flares that refused to end. That is how the story of GRB 250702B began: the longest gamma-ray burst ever observed. Typical bursts last seconds, rarely minutes. This one stretched to 25,000 seconds, beating the previous record by a factor of two.

In Euclid's deep fields, stars flare up that were not in any catalog. A telescope built to map dark matter has worked like a camera trap: one frame, and a cosmic explosion is already on record.

A firefly blinks for one ten-billionth of a second somewhere above the Siberian taiga. Seeing such a thing is impossible, but the TAIGA-HiSCORE array, spread across a valley in the Tunkinsky district of Buryatia, tried to catch exactly such flashes — not from insects, but from the depths of space.

Deep in the Siberian taiga, there are a hundred light traps: each about the size of a small table, but together they cover a square kilometer. At night, these traps gaze at the sky, catching faint flashes of light born when cosmic particles slam into the atmosphere. The setup is called TAIGA-HiSCORE, and it usually works as a giant "eye" for such particles.

In 1988, the surface temperature of the Pacific Ocean began to change long before meteorologists declared the onset of El Niño. Points on the map scattered along the equator started behaving in concert: if water warmed in one place, it did so in a neighboring one too.