cosmic dawn

Three cabinets full of rocks. In one, metallic grains and the gray mineral enstatite; in the second, the same grains but with rusty streaks; in the third, layered clays swollen with water. All three sets were pulled from meteorites that fell to Earth: chondrites. They were born in the same gas-and-dust disk around the young Sun, yet somehow turned out so different.

In July 1969, as Apollo 11 flew toward the Moon, astronauts noticed something unusual: brief flashes of light that appeared even with their eyes closed. At first, this was attributed to fatigue, but the flashes recurred in different crews. Gradually, it became clear: cosmic rays were to blame — tiny particles hurtling through space at tremendous speeds.

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.

Boiling water in a pot is a good place to start. Bubbles of steam rise, pop, and the surface settles down. Something similar might have happened in the first moments of the universe's life with a special field filling space: bubbles of a new phase inflated and collided, like islands of steam in liquid.

Two cities endure a series of fires. In one, the wind carries ash far beyond the outskirts, leaving the sky clear. In the other, ash settles as a dense veil, painting sunsets crimson. Roughly the same thing, just on a galactic scale, happens with supernova explosions, the final flares of massive stars.

Three invisible strings oscillate in the intergalactic void. This is not poetry, but a hypothesis about the nature of dark matter — an ultralight quantum field with spin 1, carrying three polarizations.

In the first moments after the Big Bang, cosmic symmetry breaking divided the hot plasma into regions with different vacuums — the lowest energy states of a field.

Two thousand years ago, a brilliant beacon shone in the constellation Eridanus, recorded in the registers of ancient astronomers. Hipparchus in 129 BCE noted it as a first-magnitude star, Ptolemy confirmed its brightness in the Almagest, and the Persian scholar Al-Sufi still saw it among the brightest in 964.

The early universe underwent a rapid expansion — inflation. In a tiny fraction of a second, minuscule quantum jitters were stretched to galactic scales and became the seeds of all large-scale structure.

Stars are born in cold clouds of cosmic dust and hydrogen. Inside these cocoons, protostars — the cores of future suns — were long thought to be just hot clumps. But it turns out many of them are powerful accelerators: they shoot out narrow jets of gas that, slamming into surrounding matter, produce invisible gamma-ray light.

A vast city lights new streetlamps every night. But then a hurricane sweeps in, rips all the fuel from the warehouses, and the lamps go out one by one. Something similar has been spotted by astronomers in a galaxy whose light has traveled 12.5 billion years to reach us.

A massive star ends its life in a spectacular collapse: the core compresses into a neutron star or a black hole, while the outer layers fly off in a dazzling supernova.

The Universe is singing. Not in the usual sense: its symphony is recorded in tiny density variations from which galaxies and ourselves grew. After the Big Bang, space was almost uniform, but quantum fluctuations during inflation left a faint pattern — slightly more matter here, slightly less there.

The origin of the hot Big Bang is one of the greatest mysteries. The familiar picture: after inflation, the inflaton field transfers energy to ordinary particles, reheating the Universe. Yet dark matter and dark energy hint that nature has hidden sectors.

The universe is expanding, and its history features two puzzling episodes that don't fit into a simple picture. The first is a brief period in its youth when everything flew apart faster than expected, as if someone had floored the gas pedal. The second is today's acceleration, as if the same pedal were pressed again, but more gently.

A street where houses have just been built. Some shine with clean windows, others are covered in construction dust. That's roughly what galaxies looked like when the universe was only a few hundred million years old. The new James Webb telescope peered into that era and saw dozens of bright star islands.

A tiny black hole, no larger than an atomic nucleus, hovers in a cloud of hydrogen. It doesn't swallow everything around it; instead, it slowly radiates away, losing mass with every moment.

The JWST telescope has spotted a multitude of bright galaxies in the young universe. Their ultraviolet light was barely absorbed by cosmic dust — defying previous expectations.

Axions are hypothetical elementary particles introduced in 1977 by Roberto Peccei and Helen Quinn to resolve the so-called strong CP problem in the Standard Model of particle physics.

There is something wildly generous about a garden where the first flowers don't just bloom but immediately scatter their seeds far beyond the fence. Something similar was happening in the young universe.

An old chest of family heirlooms opens, and inside lie jewels that were thought to be as old as great-grandmother. But suddenly it turns out: the gold was remelted, the stones were recut, and this happened much later than thought. A similar story happened to the oldest particles in meteorites — calcium-aluminum inclusions, or CAIs.

After the Big Bang, the Universe was filled with cold gas — mostly neutral hydrogen and helium. It enveloped the cosmos like a morning fog, impenetrable to light. The Dark Ages began. When the first galaxies ignited, their radiation, like a searchlight beam, started knocking electrons out of atoms.

Light from a distant quasar, the bright core of a galaxy, passes by a massive galaxy and bends, like a flashlight beam through uneven glass. If the lens and source align almost perfectly, we see not one quasar but several copies.

After the Big Bang, the Universe simmered as a fiery 'soup' of fundamental particles. Expanding and cooling, the soup gradually 'solidified' into protons and neutrons — much like crystallization. Had the solidifying been instantaneous, like a lake cracking in a deep freeze, the fabric of spacetime would have convulsed.

Dark matter is an invisible substance that keeps galaxies from flying apart. If its particles occasionally decay near the Sun, they shoot out streams of fast particles, like invisible hammers striking light. Each impact turns a particle of sunlight into a gamma ray — a super-powerful flash that telescopes can spot.

In the first instants after the big bang, the universe was a quantum vacuum where pairs of particles and antiparticles, virtual "guests" from physical nothingness, spontaneously appeared and almost immediately annihilated.

At the dawn of Earth, about four billion years ago, the planet was a harsh place: a dim sun, frequent asteroid impacts, and air without oxygen. Under such conditions, the first steps of life seem almost impossible.

Light from a distant galaxy traveled to us for 13.4 billion years. The James Webb Space Telescope caught it and split it into colors. The spectrum shows a bright hydrogen line, like a fingerprint saying that galaxy GS-z13-1-LA is actively forming stars. Young hot stars inside the galaxy act like floodlights.

Long before stars appeared, the universe was filled with cold hydrogen. This gas can 'sing'—emitting radio waves with a wavelength of 21 centimeters. When the first stars and galaxies ignited, their ultraviolet light began to strip electrons from hydrogen atoms, turning neutral gas into ionized gas.

The first stars ignited from clouds that contained nothing but hydrogen and helium. Heavy elements (carbon, oxygen, iron) came later, forged inside stars. But among those pioneers, there could have been lightweight stars, with masses just below that of the Sun.

The night sky looks dark, but it's actually filled with a faint glow. Most of this light is born in invisible clouds of cold gas — the very stuff from which new stars emerge. This gas barely emits, making it hard to spot. But sometimes it gives itself away through radio waves emitted by carbon monoxide (CO) molecules.

The oven that once baked the first stars has long gone cold, but crumbs from that bread remain. These crumbs are carbon atoms scattered on the surfaces of old stars in tiny satellite galaxies of the Milky Way. Such galaxies are called ultra-faint dwarfs: each contains only a few thousand stars and shines barely perceptibly.

In cold clouds of interstellar gas, carbon hides inside carbon monoxide (CO) molecules, like sugar dissolved in tea. But near hot, massive stars, this 'tea' boils: harsh radiation tears the molecules apart, and carbon escapes as lone atoms or ions.

A few hundred million years after the Big Bang, the universe resembled an endless dark ocean, shrouded in a thick fog of neutral (non-ionized) hydrogen. Then something dispersed the gloom: ultraviolet radiation knocked electrons out of atoms, making the gas as transparent as pure water.

A massive galaxy cluster acts as a giant lens. Its gravity warps the fabric of space, and the light of distant objects, bending around this curvature, is amplified and split into multiple images.

By analyzing color indices — the ratio of brightness in different spectral bands in images from the James Webb Space Telescope, astronomers have identified galaxies whose light cuts off sharply in the ultraviolet.

The Sun’s gravity creates an invisible goblet, in which dark matter of a special kind — ultralight — doesn’t splash around chaotically, but occupies strict energy steps, like transparent layers of liquid. So around the Sun, a natural spectroscope emerges, sorting the invisible substance into levels, just like electrons in an atom.

After the Big Bang, the universe was hot and dense. In clumps of dark matter, invisible stuff felt only through gravity, its particles, colliding, annihilated, giving birth to powerful radiation. This hidden heat, like an invisible furnace, warmed gas clouds from within.

The James Webb Space Telescope looked back to a time when the universe, just after the Big Bang, was only a billion years old, and found the 'Sleepy' galaxy. Unlike its neighbors, which shone with young stars, it looked tired and dim.

The universe exists in a state of false vacuum, like water behind a dam. Behind it lies the true vacuum — an abyss with different laws. Normally, water can only seep through the pores in a thin trickle (a quantum effect), barely changing the level.