substance

gas

A state of matter, often hydrogen and helium, that fills protoplanetary disks.
53 related articles

Description

Gas is one of the four fundamental states of matter, characterized by particles that are widely separated, move freely, and fill any container they occupy. In the context of planetary science and astrophysics, gas—primarily hydrogen and helium—is the raw material from which stars and planets form. Protoplanetary disks, the swirling clouds of gas and dust around young stars, are the birthplaces of planets. The behavior of gas in these disks, including its turbulence, pressure, and temperature, determines how dust grains clump together to form planetesimals and eventually planets. Gas also plays a critical role in the atmospheres of planets, influencing their climate and habitability.

History

The concept of gas as a distinct state of matter was formalized in the 17th century by scientists like Robert Boyle and later developed by Daniel Bernoulli, who proposed the kinetic theory of gases in 1738. The role of gas in planet formation became a major focus of astrophysics in the late 20th century with the discovery of exoplanets.

How it works

In a gas, particles are in constant random motion, colliding with each other and with the walls of any container. The pressure of a gas is the result of these collisions, and its temperature is a measure of the average kinetic energy of the particles. In protoplanetary disks, gas orbits the central star, but pressure gradients and turbulence cause it to move slightly slower or faster than the Keplerian orbital speed. This drags dust particles, causing them to spiral inward and collide, eventually growing into larger bodies. The gas also provides the material for giant planets like Jupiter and Saturn, which accrete massive envelopes of hydrogen and helium.

In practice

Understanding gas behavior is essential for modeling planetary atmospheres, predicting weather, and designing industrial processes like gas turbines and chemical reactors.

Fun fact

In the early universe, the only elements were hydrogen and helium gas; all heavier elements were forged later in stars and supernovae.

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Related articles · 53

A Pressure Cooker with Three Settings: How Disk Gas Forged the First Rocks
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.
Stellar2026-08-102 minarXiv:2608.09896
Planetary Kitchens: What the Pantries of Taurus Hide
In the dark kitchen of the Taurus molecular cloud, 450 light-years away, dozens of planetary systems are being prepared. Each young star is a chef, and its protoplanetary disk is a counter piled with flour-like dust and steam-like gas.
Exoplanets2026-08-101 minarXiv:2608.10094express
Flip-Flop Molecules Reveal Gaps in Planet-Forming Disks
Around young stars, flat clouds of gas and dust swirl: these are future planetary systems. Inside some of them, a void gapes: the dust and gas have been swept away, as if someone thinned out the middle of a vinyl record.
Stellar2026-08-072 minarXiv:2608.07331express
The Stellar Family Tree of Planets
A star is not just a distant sun. It's a cradle for planets, and its light carries the birth story of the entire system. The chemical composition of a star is its DNA. Astronomers peer into this DNA to understand why some stars host rocky worlds like Earth, while others host gas giants.
Still Particles Come Alive in a Crowd
At a concert, moving through a dense crowd is tough — the tighter the pack, the less you want to move. That's how active matter usually behaves: swarms of bacteria or robot flocks freeze in tight quarters. But one research group found the opposite effect.
A Quieting Fountain: Evolution of Protoplanetary Disk Winds as Seen by JWST
Seventy-two protoplanetary disks, swirling cocoons of cosmic dust and gas, came under the gaze of the MIRI instrument on JWST. Most of them shoot outflows into space: dense conical structures and narrow, high-speed jets. They blast like fountains. This process is not accidental.
Cosmology2026-07-163 minarXiv:2607.15028
How Galactic Dust Traps Heat from Invisible Black Holes
Dark matter is invisible to telescopes, but its gravity was revealed half a century ago by Vera Rubin. Since then, physicists have explored dozens of hypotheses, and one of the most elegant is primordial black holes, formed in the first moments after the Big Bang.
Icy Origins: Most Hot Jupiters Come from the Cold
Among the scorching exoplanets that circle perilously close to their stars lies the secret of their birth. Nearly three decades ago, Michel Mayor and Didier Queloz discovered the first such world, and since then astronomers have been tormented by the question: how does a gas giant end up pressed against…
Cosmic Kick: Warm Orphans Born from Stellar Death
Like an exquisite clockwork mechanism, a multi-planet system responds sensitively to the slightest nudge. And when the star at the heart of this mechanism dies, shedding its envelope and turning into a white dwarf, even a modest kick at a speed of 0.75 km/s can trigger a cascade of events, flinging entire worlds into interstellar emptiness.
Exoplanets2026-06-292 minarXiv:2606.30644express
How Giant Planets Hide Hydrogen Inside
A sub-Neptune is a planet that falls between Earth and Neptune in size. These worlds are abundant in our galaxy, but their internal structure has been hotly debated. New research shows that in their youth, these planets behave like a sponge soaked with water.
High Energy2026-06-171 minarXiv:2606.19445express
Young Stars: Gamma Rays from Jets
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.
Exoplanets2026-06-161 minarXiv:2606.18219express
Inside Uranus and Neptune Lie Oceans of Magma
Previously, Uranus and Neptune were considered ice giants because of assumed thick layers of frozen water, methane, and ammonia. New calculations paint a different picture: deep inside them hides an ocean of hot magma, which under immense pressure has absorbed a colossal amount of hydrogen.
Exoplanets2026-06-121 minarXiv:2606.14646express
A Volcanic Planet Breathes Hydrogen
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.
Exoplanets2026-06-091 minarXiv:2606.10888express
Heavy water ice found in planet-forming disk
The James Webb Space Telescope peered into a disk of gas and dust around a young star where planets are born, and for the first time spotted ice made of heavy water. This water is not ordinary: in its molecules, regular hydrogen is replaced by deuterium, its heavier sibling.
Exoplanets2026-06-092 minarXiv:2606.11344express
Young Star Flares Hinder Planet Formation
A thick stew slowly cools in a pot. Suddenly, the flame beneath it flares up, and the stew begins to boil, breaking into many small whirlpools. Much the same happens to the disk of gas and dust around a young star when it experiences a flare — a sudden influx of matter from the disk onto the star.
Comet Spice: How a Late Influx of Matter Reshaped the Outer Solar System
Putting together the Solar System is like crafting a high-end tasting menu: the recipe isn't always set in stone — sometimes the final ingredient is added while the dish is already cooking.
Steam from Scorching Rocks: Silicon Gas in the Atmosphere of TWA5B
The young super-Jupiter TWA5B, a scorching ball 25 times Jupiter's mass, floats just fifty light-years away. Its faint infrared glow long hid its chemical makeup. Now, high-resolution spectroscopy with CRIRES+ has registered the ghostly trace of SiO — silicon monoxide.
Exoplanets2026-05-312 minarXiv:2606.00974express
A Sulfur Key to Planetary Childhood
A kindergarten where some kids are busy making sandcastles while others are already assembling building blocks. That's roughly what the V1298 Tau system looks like: it's only 20 million years old — by cosmic standards, it just left the nursery. Several planets orbit it, and two of them, b and e, turned out to be surprisingly different.
Exoplanets2026-05-252 minarXiv:2605.26216express
Planetary Budget Doesn't Add Up
The cosmic accounting has hit a snag. The bookkeeper is balancing the books: in one column, all the planets astronomers have counted in the galaxy; in the other, the stockpile of building material in the dusty cocoons of newborn stars. The numbers don't line up. Even if you gathered every last grain of dust and molded it into planets, there wouldn't be enough material.
Galaxies2026-05-202 minarXiv:2605.20590express
Where Dwarfs Ignite Stars
In a city park, trees grow faster than in a deep forest — not because the soil is better, but because branches collide and seeds are exchanged more often. Galaxies in the Spiderweb protocluster behave much the same way. This vast clump of matter will become a mature cluster billions of years from now.
Exoplanets2026-05-122 minarXiv:2605.11486express
Dust Rings at the Edge of a Distant System
A huge rotating pancake of gas and dust surrounds a young star. In such a "maternity ward" for planets, rings and gaps are often seen, as if an invisible plow had carved furrows. These are usually attributed to already-formed planets that clear paths with their gravity.
Exoplanets2026-04-202 minarXiv:2604.18332express
Dust Halos Around Young Stars
A young star is surrounded by a flat, rotating disk of gas and dust, like pizza dough that's been spun out. Planets are born inside such a disk. But around three stars (Elias 2-24, IM Lup, and DM Tau) astronomers noticed something odd: far beyond the edge of the bright disk stretches a barely visible but enormous dust halo.
Exoplanets2026-04-132 minarXiv:2604.11262express
Dust Against the Wind: How Planets Are Born
In a disk of gas and dust around a young star, dust particles behave like sand grains in a stream of water: the gas flows faster, the dust lags behind, and friction arises between them. This friction can rock the magnetic waves that run through the disk. The galaxy is full of such disks: it is precisely in them that planets are born.
Stellar2026-04-131 minarXiv:2604.11904express
Stellar Wind Kicks Up Dust
A newborn star is like a kitchen mixer: it whips up the surrounding cloud, and splatters fly in all directions. Only instead of batter, it's gas and dust. Previously, astronomers had only seen gas jets, and dust was considered too fragile: the shock wave should shatter dust grains into atoms.
Proteins Frozen in Flight
Imagine trying to examine a snowflake without letting it melt or get damaged. That's roughly the challenge facing scientists who want to study individual proteins — the tiny molecular machines of life. In solution, a protein constantly jiggles and clumps with its neighbors, and in an electron microscope, the beam destroys it.
Exoplanets2026-04-081 minarXiv:2604.06809express
Carbon-Rich Stars Give Birth to Giant Planets Farther Out
A baker adds more sugar to the dough, and the pie turns out different. So it is with a star: the composition of its "dough"—the cloud of gas and dust from which planets are born — determines what worlds will form around it.
Galaxies2026-04-062 minarXiv:2604.04501express
Chaos Reigns in the Thick of Stellar Filaments
In cold clouds of interstellar gas, long, dense filaments stretch out. Inside them, like overcrowded incubators, future stars are maturing. For a long time, it was thought that within such filaments, everything was governed by gravity: matter smoothly flows toward the centers, where density increases and eventually a star ignites.
Exoplanets2026-03-291 minarXiv:2603.27598express
How to find life on other planets: a new method
A chemical detective searches for life on other planets. Its tool is a mass spectrometer that identifies molecules by weight (the same device earthly forensic scientists use to analyze clues).
Exoplanets2026-03-272 minarXiv:2603.26876express
Icy Pebbles: Why Some Comets Are Rich in Carbon Monoxide
In the cold outer reaches of the Solar System, water is considered the main building material for ices. But some comets and distant icy bodies have an unusually high ratio of carbon monoxide (CO) to water, as if a scoop of ice cream suddenly had too much syrup. The authors of a new study set out to find where this imbalance comes from.
Exoplanets2026-03-221 minarXiv:2603.21360express
Where Earth's Iron Came From
When a baker kneads dough, the grains of flour can tell you which mill they came from. It's the same with Earth: the composition of iron in its depths preserves a memory of where the pieces that assembled the planet were born.
Exoplanets2026-03-191 minarXiv:2603.18769express
Acid for Life: Why Cyanide Is No Obstacle
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.
Exoplanets2026-03-182 minarXiv:2603.18206express
Superflares of Young Stars: Greenhouse Effect and Prebiotic Synthesis of Amino Acids
In its youth, our Sun radiated about 30% less energy than it does today: this faint young Sun paradox long troubled planetary scientists: with such a heat deficit, Earth's oceans should have frozen, yet geological evidence says otherwise.
Instrumentation2026-03-171 minarXiv:2603.16981express
A Comet with a Steering Wheel: Four Engines for an Interstellar Voyage
An icy rock is flying through the Solar System on an open trajectory — coming in from interstellar space, swinging around the Sun, and heading back into the dark.
Exoplanets2026-03-171 minarXiv:2603.17195express
How Dust Gathers into Planets
Planets are born from dust. In a disk around a young star, tiny dust grains collide, stick together, and gradually grow like a snowball rolling down a hill. But there's a catch: the gas in the disk moves faster than the dust and drags on it, preventing it from clumping into large chunks. For dust to stick together, there needs to be enough of it.
Exoplanets2026-03-161 minarXiv:2603.15810express
Dust Grains Dance a Waltz
In a protoplanetary disk, a cloud of gas and dust around a young star, dust grains don't just fly in circles. They are carried by the gas flow, like sand by the wind, and in turn alter that flow. Layers emerge, sliding past each other, and at their boundaries an instability arises — waves and vortices.
Galaxies2026-03-122 minarXiv:2603.12200express
Dust in Galactic Winds: How to See the Invisible
At the center of every large galaxy, including our own Milky Way, resides a supermassive black hole. It doesn't just sit there — sometimes it pulls in gas and dust, and part of that material is blasted back out in powerful outflows. These outflows, or "winds," carry material far from the center and affect the entire galaxy.
Exoplanets2026-02-192 minarXiv:2602.17367express
How Planets Were Born: Clues in Meteorites
The young Solar System resembled a giant construction site: around the newborn Sun swirled a disk of gas and dust, and from this dust gradually assembled stones, boulders, and then planetary embryos — planetesimals. Today, their fragments fall to Earth as meteorites.
Exoplanets2026-02-131 minarXiv:2602.12522express
A Warm Pocket in a Cold Disk
The young star PDS 66 is surrounded by a flat disk of gas and dust — the cradle of future planets. In the cold outer regions of such a disk, silicon and sulfur are usually hidden inside dust grains, but astronomers spotted a bright patch of gas at about 60 astronomical units from the star.
Exoplanets2026-02-103 minarXiv:2602.09422express
Four Giants and Traces of Snow Lines
130 light-years away, four giant planets orbit the young star HR 8799—each 5 to 10 times more massive than Jupiter. They lie far from the star, at distances from 15 to 70 astronomical units (one astronomical unit is the distance from Earth to the Sun).