tidal migration

A million orbits: the same score. Nine dark matter halos: nine orchestras without a conductor. All musicians play from the same notes, but in each hall the music sounds different: sometimes in tune, sometimes out of sync. Likewise, satellite galaxies falling into a host halo follow orbits that depend not only on mass but also on the shape of the invisible stage.

A neutron star is the remnant of an exploded star, compressed so tightly that a teaspoon of its material would weigh as much as a mountain. Inside such an object, protons and neutrons are packed tightly together, and under enormous pressure, hyperons, particles containing a strange quark, can appear.

The solar wind is a continuous stream of charged particles flowing from the Sun. It has two main components: protons (hydrogen nuclei) and alpha particles (helium nuclei, four times heavier).

A disk of gas and dust spins around the young star HV Tau C, nearly edge-on to us. The James Webb Space Telescope examined its spectrum and detected the glow of hot molecular hydrogen (H₂). This revealed a wide, bipolar wind blasting from the inner regions far beyond the disk.

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.

The star AB Aur is young, about 4 million years old. Around it swirls a dense disk of gas and dust. Recently, a long gas stream, a flow of material from the surrounding cloud, crashed into it.

Imagine a spiral staircase with balls rolling down. Some are twisted to the right, others to the left. The steps are arranged so that right-twisted balls slip through faster, while left-twisted ones get stuck. Something similar happens inside helical molecules — for example, in the double helix of DNA.

Every 165 days, the giant planet dives toward its star, nearly grazing its fiery corona, then flies off into the icy void. This is TIC 241249530 b — an exoplanet with a record eccentricity of 0,94.

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…

A quarter-century ago, Michel Mayor and Didier Queloz discovered the first hot Jupiter, and shattered all the rules of planet formation. A gas giant on a days-long orbit couldn't have formed next to the star: it's far too hot and lacks building material. So, it must have been born far away and then migrated.

Forget the familiar images of planetary cores — a sharp boundary between rock and gas is a thing of the past. The Juno probe, diving into Jupiter’s gravitational field, and Cassini, into the embrace of Saturn, discovered that heavy elements are not gathered at the center but smeared over a vast region, as if someone carelessly shook a cocktail.

In the coastal shallows, where water retreats and returns, life follows the rhythm of the sun. The brownish film on the mud's surface is not just dirt but a dense community of tiny diatoms. By day they get plenty of light for photosynthesis, but when the sun gets too intense, a chemical storm brews inside the cells.

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.

A ball, almost weightless for its size, circles its star every four days. Planet TOI-2195 A b is a real riddle: by mass it's slightly heavier than Neptune, yet bloated to Jovian volumes. If there were an ocean big enough, this exoplanet would float on its surface like a giant inflatable ball.

At the center of attention are tiny stellar cities: ultra-faint dwarf galaxies. They resemble sparse swarms of fireflies circling within a vast invisible cloud. This cloud is a halo of ultralight dark matter. Its particles are so light that they behave not like billiard balls but like waves.

The giant cloud of icy chunks on the outskirts of the Solar System, the Oort cloud, resembles a transparent bubble stretched to a light-year across. Usually, these chunks hang quietly in their distant corners, but sometimes something disturbs them. Most often, it's the tidal influence of our Galaxy.

At the heart of nearly every large galaxy shines an active nucleus — a supermassive black hole surrounded by a flat, rotating disk of incandescent gas. The disk itself flickers, but astrophysicists suspect that within it lurks a whole swarm of small, stellar-mass black holes.

A scorching rocky planet is like a pot of boiling soup, except its lid is the atmosphere. Gases escape from the magma, wrap the world in a thick blanket, and in turn influence how quickly the celestial body cools. For GJ 1132 b, which orbits so close to its star that a year lasts just one and a half Earth days, this connection is especially important.

A pot of boiling soup is shaken hard — the liquid sloshes, waves crash against the walls. Something similar happens inside a gas planet when it swings past its star on an elongated orbit. The star's gravity excites powerful internal waves in the planet, known as tidal fundamental modes. These waves can completely change the planet's fate.

When two neutron stars circle each other, they don't remain rigid spheres. The partner's gravity stretches each star, creating tidal bulges — much like the Moon raises ocean tides on Earth. But unlike water, here it's superdense matter that deforms: a teaspoon of this stuff weighs billions of tons.

The planet WASP-121 b is a gas giant, heated to 2500°C. It always faces its star with one side, like a globe frozen under a lamp. But as it passes in front of the star's disk, its rotation reveals different facets to us — as if that globe were slowly turned, letting us peer into every corner.

In 5 billion years, the Sun, having exhausted its fuel, will start to swell, turning into a red giant. Like a balloon losing air, the star will weaken its gravitational grip, and Earth — a grain of sand on an invisible thread — will drift to a more distant orbit.

At the center of a distant galaxy, a supermassive black hole is surrounded by a flat, rotating disk of gas and dust — a giant cosmic funnel of matter. A small compact object, such as another stellar-mass black hole, may find itself in this disk.

On the periphery of the Solar System lurk thousands of objects comparable in size to an exoplanet — a body of planetary mass not bound to our star. Their orbits are chaotic, and from time to time the trajectory of such a wanderer crosses Earth's path.

A blob of cold helium swoops dangerously close to a black hole. But this isn't just a blob: it's a dead star the size of Earth, yet with a mass comparable to the Sun's.

A planet the size of Neptune wandered too close to its star. The star begins to pull the planet's outer layers onto itself — gas streams off the planet like water from an overflowing bucket. This process is called Roche-lobe overflow (astronomers use this term for the boundary beyond which a star can tear material away from a planet).

Picture a tightrope walker balancing over an abyss. Every step changes the rope's tension, and the slightest shift in center of gravity can prove fatal. That's roughly what the dance of an ordinary sun-like star around a black hole of ten solar masses looks like when the orbit is highly elongated.

Eight hundred million years ago, in the main asteroid belt, a giant inkwell shattered. The parent body, over a hundred kilometers in diameter, made of primitive carbonaceous chondrites, suddenly broke apart near the J3:1 resonance with Jupiter.

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.

A black hole rips apart a star, and we see a dazzling flare. Then, a couple of years later, when everyone has forgotten about it, radio telescopes suddenly pick up a new signal, like an echo from the past.

A tightly stretched sheet lies on a table for days. Outwardly it's still, but the fabric fibers retain tension — loosen one edge slightly, and wrinkles will run across it, rearranging the whole pattern. That's roughly how a layer of epithelial cells behaves at rest. It doesn't just freeze; it accumulates mechanical stress — a kind of cellular memory of past movements.

Planet WASP-121 b always shows the same face to its star, like a rock in a campfire. The dayside is so hot that ordinary hydrogen, the very stuff most of the universe is made of, can't take it: its molecules tear apart into individual atoms, and the temperature flips upside down: the higher you go, the hotter it gets.

In a pot of boiling soup, churning currents carry heat to the walls, and the soup cools. In a tokamak, a huge magnetic bottle for plasma, the same thing happens: turbulent eddies carry energy outward, hindering the ignition of a fusion reaction. But sometimes the plasma seems to find a way to calm itself.

The carousel spins all the horses in one direction, but one stubbornly gallops against the flow. That's exactly how the planet TOI-1710 b behaves around its star. Using the HARPS-N and GIANO-B instruments, astronomers measured its tilt at 149 degrees. That's nearly a 180-degree flip, meaning the planet orbits "backward" relative to the star's rotation.

The binary star TIC 287869463 is a close pair: one star pulsates like a bell, while the other's gravity stretches it like an ocean tide. Usually, pulsations travel across a star as waves, but here one wave has frozen in place. Astronomers sifted through three years of data from the TESS telescope — light from 50,000 stellar pairs.

Two stars orbit a common center, accreting gas from a surrounding cloud. Rotating disks of gas form around each star and around the pair as a whole. From these disks, jets shoot out like hoses. Inside the disks, gas is constantly churned — that's the magnetorotational instability at work.

Lithium is like a thermometer dipped into a star's interior. This light element is destroyed at temperatures around 2.5 million degrees, so its abundance on the surface tells us how deeply the star's material has been mixed.

The James Webb Space Telescope is gazing more and more at exoplanets — worlds orbiting alien stars. Some of them are scorching rocky spheres, tidally locked with one side forever facing their star. There, rock melts into oceans of liquid lava. How does this lava move?

A black hole can torment a star for years, rather than rip it apart immediately. Tidal forces are when the hole's gravity stretches the star: the near side is pulled harder than the far side. Usually, getting too close rips the star apart instantly — that's a tidal disruption event.

The Kepler telescope spent years watching thousands of stars, spotting planets by the tiny dips in starlight when a planet passes in front of its star. Such a passage, or transit, lets us measure the planet's size but not the shape of its path.