helium burning

A gas target is like a funnel: the steeper its walls, the stronger the flow. But in this funnel, it is not water that flows, but ultraviolet light, born when a powerful laser pulse passes through a cloud of argon. The efficiency of this conversion is usually minuscule, about 0.001%: out of a thousand laser photons, only one turns into useful ultraviolet.

Two spinning tops whirl so close they nearly touch. One is scorching blue, the other dim white. Together they complete a full orbit in twenty hours. This is the pair Feige 64: a blue star with a mass of just a third of the Sun's, and a white dwarf, the cooled core of a former star, one and a half times heavier than our Sun. The blue star seems too hot for its mass.

In a dense molecular cloud, at the edge of glowing gas, an invisible assembly line is at work. It takes simple scraps — single atoms and light pairs — and glues them together step by step into long carbon chains and rings. The first piece of this assembly line has long eluded our eyes. Now it has been found.

In dark interstellar clouds where new stars are born, chemistry starts with a tiny particle — the trihydrogen ion (H₃⁺). It collides with other atoms and sets off a cascade of reactions that build ever more complex molecules. For a long time, it was thought that the main reaction producing it, H₂⁺ colliding with H₂, only happens in the gas phase.

In the deep field of JWST, among thousands of galaxies, astronomers zoomed in on the source JADES-GS 209777 – and saw a cosmic chick. Its "shell" is a thick cocoon of gas and cosmic dust that long hid the growing black hole at its center. But at a redshift of 3,711 (1,8 billion years after the Big Bang), the shell began to crack.

Through three minutes after the Big Bang, the Universe played its first symphony. It was the big bang nucleosynthesis — the formation of light nuclei, where each element sounded its own note, and the tempo was set by the expansion of space.

Erwin Schrödinger pondered how life maintains order despite the second law of thermodynamics. He could never have imagined that part of the answer lies hidden in the instability of giant stars.

For a long time, astronomers searched for the 'factories' of the most energetic cosmic rays — particles that carry the macrocosm compressed to the size of an atomic nucleus. Colossal star-forming regions like Cygnus OB2, where winds from young giants collide, were prime suspects.

In a giant cosmic cradle, the Tarantula Nebula, astronomers took a close look at 122 massive stars, each at least 30 times heavier than the Sun. They measured the nitrogen abundance in their atmospheres, and the picture turned out to be unexpected.

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.

When two neutron stars, the ultra-dense cores of dead stars, collide, a kilonova is born: an explosion a thousand times brighter than a typical nova. This is the universe's true smelting works. In the scorching cloud racing outward at near-light speeds, a furious flux of neutrons transmutes atomic nuclei into gold, platinum, osmium.

In the scorching core of a star, two helium nuclei approach each other like two dancers on a crowded stage. Their dance is alpha scattering, the basis of stellar helium burning. How smoothly they twirl determines how quickly the star burns its fuel. Previously, this dance was described in simplified terms.

A collision of two neutron stars is a cosmic forge where the heaviest elements of the periodic table are hammered out in seconds. In 2017, detectors picked up gravitational waves from such a merger, and telescopes saw a flash — a kilonova.

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 planet the size of Neptune, but glowing white-hot. Beneath the clouds lies an ocean of magma capable of absorbing an entire hydrogen atmosphere. The new SEAMIST model is the first to trace how such dissolution changes a planet's fate from birth to old age. The big surprise is the mechanism of catastrophic boiling.

Two guitar strings are stretched on the same neck. They are almost identical, but one is slightly shorter — and they sound different. That's roughly how the two isomers of ethanimine work: molecules with the same set of atoms but rotated differently in space. Astronomers spotted this molecule in the dense clouds near the center of our Galaxy.

In April 2021, in a galaxy 35 megaparsecs away, supernova SN 2021foa erupted. It immediately puzzled astronomers: its spectrum feverishly switched between hydrogen and helium lines — as if the star, in agony, was frantically shedding its outer layers.

Deep inside the detector at the Large Hadron Collider, protons collide, and for a fleeting moment something heavy is born. It instantly shatters into two Higgs bosons — particles that, like nesting dolls, each hide two pairs of b-quarks.

In an orchestra, each musician plays their own part, but at a certain moment all instruments pause on a single note. Cosmic rays behave somewhat like this — particles flying toward us from distant stars.

Two burned-out stars, each about the size of Earth but heavier than the Sun, spiral ever closer until one crashes into the other. The impact triggers a thermonuclear explosion, giving birth to a type Ia supernova. Such flashes serve as cosmic beacons for measuring distances across the universe. Yet the details of their origin remain hotly debated.

Atomic nuclei are wrapped in fluffy electron coats — in such attire, they can't get close enough to embrace. But swap the light coat for a heavy one: a muon, a particle from the standard model, shrinks the cloud by nearly 200 times.

A pot of boiling porridge, where instead of grains there are layers of oxygen and silicon, and the fire beneath is about to go out, and the star will collapse in on itself. Until now, astrophysicist cooks have used a simplified recipe: they assumed that bubbles and eddies in the porridge obey one and the same average temperature throughout the depth.

An archaeologist holds in their hands not a clay shard but an actual star — a living snapshot of the era when the universe was just learning to produce anything heavier than lithium. That is exactly the kind of find astronomers describe in a new study. They spotted four dim stars so ancient and pristine in composition that their matter is barely diluted by the 'cosmic dust' of later generations.

Be stars are rapidly rotating luminaries with bright gas disks. Usually, a companion star spins them up: mass flowing from the neighbor whirls the star like a bullet in a rifled barrel. But there are also lone Be stars without a partner: their origin long remained a mystery. New research shows that solitaries can be born from a supernova explosion.

A pot of boiling soup that suddenly starts cooling at a breakneck pace: that's roughly what the universe looked like a few minutes after the Big Bang. As the temperature dropped, the first nuclei began to stick together from protons and neutrons: hydrogen, helium, deuterium, and lithium.

In cold clouds between the stars, dust grains are coated with ice, like windows covered with frost in winter. On this icy crust, chemical reactions take place that do not occur in gas. One such reaction is the encounter between a carbon atom and a nitrogen molecule.

A neutron star is the remnant of an exploded star, compressed to the size of a city. On its surface, a thermonuclear fire sometimes erupts: accumulated gas explodes like a giant hydrogen bomb. After the burst, ash remains — a mixture of heavy elements that rises to the surface and forms a hot atmosphere.

An ordinary atomic nucleus is like a tight ball: protons and neutrons are packed closely together. But some light nuclei, such as helium-6, are different. Two neutrons seem to step aside and form a dilute cloud around the nucleus — called a halo.

Deep inside a massive star, before it explodes, layers sit on top of each other like the layers of an onion. Sometimes two adjacent layers, the carbon and oxygen layers, mix together. It's like how layers of broth and vegetables in a pot of soup blend when you stir them with a spoon.

A cosmic neon sign lit up in an incredibly distant galaxy: almost all its light comes from hot gas, and the stars are lost in this glow. The James Webb telescope recorded that the gas, a mix of hydrogen and helium, is so heated that it glows on its own.

A neutron star is the remnant of an exploded star, compressed to the size of a city. In its core, matter is packed so densely that a teaspoon of such material would weigh as much as a mountain. At such densities, as predicted by the theory of strong interactions, particles acquire 'twins'—parity partners.

In April 2023, Japanese satellites detected a super-intense X-ray burst on the neutron star MAXI J1752–457. The star cooled down in 4 days — five times faster than usual. Like someone cracked open a cosmic window.

In a cloud where massive stars are being born, there is a hot, dense core. Like a crowded kitchen where the heat of the stove makes smells evaporate, here the warmth from young stars evaporates molecules from the surface of cosmic dust grains.

In the dark, cold clouds where stars are born, dust grains are covered with an icy crust. Across this crust, like on a winter road, individual atoms wander slowly. Calculations show that it is precisely these wandering oxygen and nitrogen atoms that kick off the assembly of the HNSO molecule — a compound of hydrogen, nitrogen, sulfur, and oxygen.

In stellar nurseries, massive stars are not born alone but in pairs. Two stars orbit a common center, and the more massive one expands first and begins to shed its outer layers. Some of this material doesn't escape into space but flows onto the companion, like water from an overflowing cup into a cup held beneath.

Inside every cell, chemical reactions are constantly underway, like a tiny kitchen where protein chefs whip up essential compounds. But seeing exactly how a chef prepares a dish is tricky when you're surrounded by a crowd of other molecules.

Chemistry has two worlds: in one, the catalyst is a solid particle and the reaction happens on its surface; in the other, it's a dissolved molecule where everything occurs around a single metal center. These worlds rarely meet. But in a new study, they collide. The researchers took iron oxide, a black powder used in magnetic tapes, and scattered single rhodium atoms across its surface.

A cosmic dust grain is covered in ice, and on this ice, like in a tiny kitchen, molecules are cooked. One of them is methanol, an alcohol that serves as a building block for more complex compounds in space. Previously, it was thought that methanol only forms when hydrogen atoms stick one by one to a carbon monoxide molecule.

In every leaf, in the light, a factory works that splits water into oxygen and hydrogen. The oxygen goes into the air we breathe, and the plant uses the hydrogen for food. The heart of this factory is a protein complex with four manganese atoms and one calcium atom.

Fresh after the Big Bang, the Universe fizzed like a freshly poured soda. All of space was filled with bubbles — regions of new vacuum, the kind governed by the Standard Model, pushing out the old unstable state. The walls of these bubbles accelerated to near light speed, and in head-on collisions they crumpled and burst, unleashing monstrous energy.