stellar planetary misalignment

In a dense cloud of gas and dust where massive stars are born, two young stars recently passed very close to each other. Their dance has lasted only about sixty years, and astronomers have now seen it in detail for the first time.

Astronomers catch distant planets by the trembling of their stars: an invisible companion tugs the star toward us and away, and its light subtly shifts in color. But that trembling tells only half the truth. If the planet's orbit is tilted to our line of sight, only part of its weight rocks the star, so telescopes reveal not the true mass but its shadow.

In 2015, the LIGO detectors caught the first ripple of spacetime from a black hole merger. Since then, hundreds of such events have piled up, each carrying the imprint of its ancestry: whether the holes were born together from a single pair of stars or met by chance in a dense cluster. The difference shows in the direction of their spin axes.

It's like a sprint record: to break it, you need a perfect run-up. But for sub-millisecond pulsars, the run-up is too short. The fastest known pulsar, PSR J1748-2446ad, spins 716 times per second — faster than a kitchen blender. If it were the size of Earth, a point on its equator would move at about 0.24 times the speed of light. But why doesn't any pulsar spin even faster?

26,000 light-years from Earth, in the heart of the Milky Way, star S301 tears through space at 18,000 kilometers per second. It loops around the supermassive black hole Sgr A* on an elongated orbit. At its closest approach, just 280 gravitational radii separate the star from the black hole — roughly the distance from the Sun to Uranus.

For decades astrophysicists painted a neat picture: a galaxy, like a giant carousel, spins in a unified rhythm, and the supermassive black hole at its center inherits that dance.

Dark matter remains one of the greatest mysteries of modern physics. Back when Vera Rubin observed galaxy rotation, she proved that visible matter is insufficient to keep stars from flying apart.

In a world striving for chaos, rhythm sometimes arises. The Belousov–Zhabotinsky reaction has amazed for decades: in a test tube, color waves run on their own, as if a living organism breathing matter. Something similar lurks in crystals where iron atoms balance between two magnetic states — high-spin and low-spin.

460 light-years away, around the star HD 135344B, a dense disk of gas and dust is swirling. It looks like a giant vinyl record that someone has cracked: a gap yawns in the disk, and across it, like a slender bridge, stretches a dust filament.

Imagine a person in an old photograph standing in a crowd while spinning — guessing their age would be nearly impossible. That's roughly how astronomers determine the ages and masses of distant stars, and they often get it wrong. For stars slightly heavier than the Sun (from 1.4 to 2.5 solar masses), standard methods like chemical-composition 'clocks' work poorly.

In the accretion disks that gird the nuclei of active galaxies (quasars, discovered by Maarten Schmidt way back in the 1960s) a river of incandescent gas and dust churns. In its backwaters, where turbulent flows subside, against all odds, planets are born.

Two neutron stars whirl in their final dance. If their spin aligns with their orbital motion, the partners merge neatly, launching a narrow jet of superheated matter. If they spin in opposite directions, the dance breaks apart, scattering a thick shroud of debris.

A streetlamp flickers as someone walks past. That's roughly how our nearest star, Proxima Centauri, behaves: it flares in response to the motion of its planets. Astronomers observed the star with a highly sensitive instrument, the ESPRESSO spectrograph. It captures light and splits it into colors, much like a prism.

Two swift streams of charged particles collide, and magnetic field lines begin to tear and reconnect. This process powers solar flares and auroras. It was usually assumed that all particles behave alike, like bullets from the same gun. But each particle has a tiny top: its intrinsic rotation, or spin.

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.

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.

Around young stars, disks of gas and dust swirl — the building blocks for future planets. Inside these disks, dust grains don't just fly randomly: they align along invisible lines of gas flow. Recently, astronomers noticed that dust grains in such disks behave like badminton shuttlecocks — always turning their long side into the wind.

Around distant icy bodies the size of a city, circling beyond Neptune, rings of dust and ice have been found. Small moons often whirl nearby. Mathematical analysis shows that a moon's gravity rocks the ring like a swing, making it tilt.

31 Aquilae is an aging star that has puffed up into a subgiant. It once resembled the Sun, but has since cooled and grown larger. It rotates very slowly — one full turn takes many days.

A beam of electrons, twisted like a corkscrew, slams into a proton. From the collision point, pairs of particles, a positive and a neutral pion, fly out. For the first time, physicists measured how often such pairs scatter at different angles when the electron's spin points left or right.

A young star that hasn't yet ignited its thermonuclear furnace is surrounded by a rotating disk of gas and dust. To gain mass, it needs to shed excess rotation — otherwise, material won't fall onto the star but will keep orbiting. Usually, this excess is carried away by two narrow gas jets that shoot from the star's poles in opposite directions, like two fountains.

In a tokamak, plasma is like a crowd on a narrow street: once someone starts running, everyone takes off at once. In a stellarator with a non-circular cross-section, the street is winding, with dead ends and pockets. The crowd can't gather into a single wave — people get stuck in different corners.

Three distant giant planets circle their stars so closely that a year on them lasts just a few Earth days. These worlds are called hot Jupiters, and their orbits are a real puzzle: how did they end up right next to the star if they were born far away, in the cold outskirts of the system? One key clue is the angle at which a planet orbits relative to the star's rotation.

Using the Keck telescope and spectroscopy (light analysis that reveals rotation speed), astronomers measured 32 objects: from giant planets to brown dwarfs — bodies heavier than planets but lighter than stars that never ignited.

The ACT telescope in Chile's Atacama Desert stared at the sky from 2007 to 2022. Its target: the cosmic microwave background, light that has been traveling toward us for 13.8 billion years. This light is polarized: its waves oscillate in specific planes, like strings stretched in different directions.

A spinning top tilted over a table, with a dusty pancake swirling around it. That is what a young stellar system looks like when the star's spin axis and the plane of its protoplanetary disk do not align. Until recently, astronomers did not know how common such a configuration is in nature.