galactic bulge

A filament of the cosmic web stretches through the young universe, and strung along it like beads on a necklace are galaxies. In the core of the SSA22 protocluster, which in a few billion years will become the center of a massive cluster, these beads are still hot and dusty: stars are being born inside them, and cold gas serves as fuel.

A little monster hides in a dwarf galaxy, and its neighbor feeds it. The satellite galaxy is slowly merging with a massive companion, and gas from the outer regions falls toward the center, where a black hole sits. By cosmic standards, it is not large: only 800 to 5000 solar masses, but its appetite is ferocious.

A census by body shape: that's one way to describe what astronomers did with 6348 massive galaxies. Instead of height and weight, they measured how concentrated the light is toward the center, how flattened the galaxy is, and how asymmetric its shape is. Then they ran the same measurements on galaxies from three computer models of the universe and compared the results.

At the center of an ultra-compact dwarf galaxy, a very dense stellar system spanning tens of light-years, there is a vacuum cleaner at work. But instead of dust, it sucks in gas shed by dying stars. This gas does not fly off in all directions; instead, it spirals into a funnel, a rotating disk that gradually settles onto the black hole.

At the center of a galaxy, where a supermassive black hole spins a disk of scorching gas around itself, giant stars sometimes form. They are unlike ordinary stars: the disk continuously feeds them with matter, and a star can grow to hundreds of solar masses, staying bright as long as the gas flow lasts.

Faint galaxies scattered across the Perseus cluster are like ghosts among their bright neighbors. They are so diffuse that distant objects shine through them, and they contain hundreds of times fewer stars than our Milky Way.

Light from a distant galaxy reaches us through its own dust. This dust is not a smooth haze but ragged clouds, like wisps of cotton. Old models treated it as a uniform mist, and then the galaxy didn't add up energetically: too much light disappeared in the ultraviolet and too little came back in the infrared. Astronomers did what a cook does when they dice a potato instead of tossing it in whole.

Red giants in the center of the Milky Way resemble distant lighthouses that brighten and dim. Their light pierces through dense dust, but standard distance-measuring methods fail here: the stars are too bright and unstable, and dust distorts the picture. Astronomers found a workaround.

A black hole with a mass of 35,000 Suns drifts through a galaxy's gas like a barge through fog. Its gravity rakes the material ahead of it, leaving a dense trail behind — a wake of gas. Some of that gas gets pulled into the black hole, and it grows.

In the first half-billion years after the Big Bang, galaxies grew like crazy. Gas fell in rapidly and collapsed into stars without any resistance. This period is called 'unimpeded star formation.' It's like frying pancakes on a scorching skillet without a lid: splatters fly, but nothing holds them back.

In the first moments after the Big Bang, matter and antimatter should have been created in equal amounts. But today, everything around us is ordinary matter, and antimatter is almost nowhere to be found. Where did it all go? The standard answer: a tiny imbalance in favor of matter wiped out almost all antimatter.

A black hole's shadow isn't just a black circle. Usually, we see a dark void surrounded by a glowing ring of hot gas. But if a black hole wasn't born from a dying star but has existed forever, its shadow might hide a surprise. An eternal black hole is a solution to Einstein's equations with no past and no collapse.

In the dark outskirts of our Galaxy, far from bright star clusters, millions of black holes lurk. They are invisible: they don't shine and don't noticeably accrete matter. Conventional search methods, designed for dense stellar fields, are useless here. A different approach is needed. Astronomers have proposed using the very fabric of space as a detector.

At the heart of our Galaxy lives the supermassive black hole Sagittarius A*. If an invisible companion orbits nearby, their dance can be spotted through the light of other stars. The pair's gravity works like a lens: as the black holes pass in front of a background star, its light briefly brightens and splits into two.

Imagine a factory capable of producing a million parts per hour, yet it only makes a hundred. That's roughly how our Universe behaves when viewed through the lens of entropy — a measure of disorder that, according to physics, must only increase. The main "machines" of this factory are supermassive black holes.

Deep beneath the ice of the South Pole, nearly two and a half kilometers down, an unusual telescope is at work. It is not pointed at the sky but through the Earth. Its quarry: neutrinos, nearly elusive particles that pass through planets and stars without interacting with anything.

A galaxy collision is like a slow dance in which two partners gradually draw closer. Hidden at the center of each is a supermassive black hole — an invisible flywheel with a mass of millions or billions of suns.

A gas disk with a mass of four hundred thousand suns encircles the black hole at the center of the Milky Way. Its gravity works like a gravitational rudder: slowly but inexorably turning the orbits of binary stars, driving them into the region where tidal forces tear the pair apart.

Layer by layer, artifact by artifact — an archaeologist reconstructs the history of an ancient settlement. Similarly, astrophysicists sifting through 259 records from LIGO–Virgo–KAGRA saw a clear layered structure among merging black holes.

1799 kilometers per second — that's the speed at which star S5-HVS1 is permanently leaving the galaxy. 4.8 million years ago, it was ejected from the center of the Milky Way during a close encounter with the supermassive black hole Sgr A*.

A galactic disk is like a frozen ripple on water: every disturbance leaves a trace that can be read billions of years later. When a dwarf satellite galaxy flies past or a head-on merger occurs, stars in the disk start to oscillate, like bobbers rocked by a wave.

A star's age is the key to the galaxy's history. But prying that key from nature is no simple task: unlike a tree, a star doesn't grow annual rings. Yet, its atmosphere holds a chemical code — the ratio of elements that slowly shifted as generations of stars died and new ones were born.

In 2016, astronomers saw something incredible: a distant star, named Icarus, flared up for several weeks, crossing the abyss of space. Gravitational lensing, an effect predicted by Einstein, had kicked in: a massive object bends spacetime and focuses light like a giant magnifying glass.

The James Webb Space Telescope peered into an era when the universe was less than a billion years old and spotted strange objects—'little red dots.' These are black holes with masses of millions of suns, but in very compact, chemically pristine galaxies. Standard scenarios can't grow such heavyweights that early.

The Orion Nebula is a showcase of astrophysics, a laboratory for studying star formation right in our backyard. For over a century, its light has been split into spectra, and each forbidden line whispers its own version of how many electrons per cubic centimeter.

The universe rewrites its history again and again. Where ordinary astronomy sees only a point, a black hole, gravitational waves peel back thin layers of the past, like an ancient palimpsest. The idea that black holes can grow by devouring each other, and their offspring can enter new unions, has been discussed by astrophysicists for half a century.

In the heart of a dense star cluster, a true forge reigns: here stars, like glowing blanks, collide and merge under gravity, and these mergers are not a catastrophe but an opportunity. Each strike of the stellar hammer transfers spin to the future black hole.

Imagine an ancient manuscript, where a new story is written over an old text. Over time, the upper layer wears thin, and lines of the past show through. That’s exactly how globular clusters, the oldest stellar systems in the Universe, are structured, like a palimpsest.

In the young Universe, about ten billion years ago, galaxies resembled endless fields after a thunderstorm: everywhere, giant — thousands of light-years across — clumps of star formation were boiling up, where young stars were born with unbridled energy. Today, these patches are an almost vanished species: in nearby galaxies, raucous hotbeds are rare.

The standard cosmological model ΛCDM, where dark matter and dark energy act as the chief architects of the cosmos, has predicted astronomical data with Swiss-watch precision for decades. Its foundation was laid by three geniuses.

At the center of the Milky Way, where the supermassive black hole Sagittarius A* reigns supreme (its metric first derived by Karl Schwarzschild), star S4714 makes a dizzying voyage.

When we peer deep into space, we see the past. Edwin Hubble’s law turns redshift into a time machine: light from galaxy UDS 12999 traveled to us for 7.6 billion years — more than half the age of the Universe.

A detective story unfolded in the GWTC-5 catalog. Hundreds of signals from merging black holes, captured by the detectors of Rainer Weiss and his colleagues, held the secret to the origin of the most massive and rapidly spinning stellar-scale objects.

The early Universe is often imagined as a nursery: most galaxies there are amorphous blobs, rowdy and irregular, choking on gas and bursts of star formation.

At the center of a galaxy, gravity condenses dark matter into a dense 'spike.' Such a dark spike resembles a funnel of invisible particles around a massive body. But if both the center and the particles are primordial black holes, the picture breaks down.

Nearly a decade and a half ago, the Fermi gamma-ray telescope spotted mysterious "bubbles" — giant plasma blobs, as if inflated by invisible lungs, towering tens of thousands of light-years from the Galactic center.

For 23 years, Hubble and James Webb have peered into the heart of Omega Centauri, a globular cluster where millions of stars crowd into a space just 150 light-years across. In this stellar beehive, the motion of the stars betrayed an invisible partner: a main-sequence star (one that has not yet left the main evolutionary branch) seemed to be tugged in a dance with an unseen weight.

At the center of the Milky Way, like a matryoshka doll within a matryoshka doll, lies a supermassive black hole, surrounded by a swarm of stars and an invisible shell of dark matter. This shell, or "spike," is expected to be extremely dense right at the horizon.

Cosmic black holes at the centers of galaxies are like giant banyan trees: their aerial root‑filaments stretch for kiloparsecs to harvest nourishing matter. For decades astronomers have debated: how does cooling gas from cluster atmospheres fall into the sphere of influence of a supermassive hole?

The stellar halo of the Milky Way is a galactic palimpsest: an ancient manuscript where earlier layers lie hidden beneath the visible text. For a long time, the Gaia-Sausage-Enceladus (GSE) structure was thought to be the final entry in this manuscript, the scar of a single catastrophic merger.