starspot

A galaxy is like a city: bright lights and dense buildings at the center, sparse lights and emptiness toward the outskirts. But if you watch how gas rotates in a galaxy's disk, you see that its speed barely drops at the edges. As if invisible neighborhoods keep the motion going. Astronomers have found a way to map this invisible city.

The solar corona lives its own turbulent life. Magnetic fields here are governed by the motions of the dense surface — the Sun's photosphere — but occasionally they rewrite the magnetic pattern themselves.

Inside planets and stars, in rotating oceans of plasma, turbulent flows, Coriolis forces, and magnetic tension collide. The central question is how the energy of this chaos crystallizes into a stable magnetic framework that can last billions of years.

A planet glides across a star's disk, and for a moment becomes a flashlight. It blocks a tiny patch of surface, revealing details that otherwise escape our view. That's exactly how astronomers peered into the dark spots on V1298 Tauri, a young twin of our Sun. They were aided by the James Webb Space Telescope JWST and three giant planets in orbit.

Every quantum particle has spin — an intrinsic magnetic property, like a tiny arrow. In an experiment, a beam of such particles passing through a magnet splits in two, like a coin that lands either heads or tails. That’s exactly how particles like a hydrogen atom behave.

Neutron stars are super-dense spheres of the remnants of exploded stars. Some of them we see as pulsars — cosmic lighthouses sending out radio bursts. What's inside them long remained a mystery. Physicists assumed that hidden fields could affect their structure, but it was believed that if the field is short-range, its effect is negligible.

Inside a neutron star, matter is compressed so intensely that atomic nuclei fuse into long strands and flat sheets. Astrophysicists call these structures nuclear pasta. At their surface, the density of matter plummets to nearly zero, like diving out of thick jelly into thin air. It's this sharp transition that creates the unusual effect.

A neutron star is a sphere the size of a city but with the mass of an entire Sun. Its magnetic field can tear atoms apart from thousands of kilometers away. Yet until now, it was a mystery how this field is arranged inside: whether it is twisted into tight ropes or more like neat lines radiating from the poles.

A lighthouse blinks every few seconds, but then begins to slowly brighten and dim over the course of a year. That is exactly what about a third of red giants do — huge stars in the late stages of life. Their normal pulsations take days or weeks, but on top of that, long secondary periods are visible: months and years.

The star GJ 436 is a dim red dwarf, and orbiting it is a Neptune-sized planet on a nearly vertical, tilted orbit. Astronomers spent 18 years taking spectra of this star to track its spots and flares. Suddenly, a rhythm emerged in the data that matched neither the star's rotation nor its 8-year activity cycle. This rhythm exactly followed the planet's orbit.

Neutron stars are the compressed cores of dead stars — city-sized objects with staggering density. Some of these stars become pulsars, cosmic lighthouses emitting strictly periodic radiation pulses.

The Sun's surface is dotted with dark spots — regions of extremely strong magnetic fields that restrain the boiling of hot gas. From time to time, shock waves race through a spot's atmosphere, like a gust of wind compressing the air ahead of it. The gas briefly flares brightly, and astronomers call these events umbral flashes.

A star like the Sun hums like a bell: sound waves inside make its surface tremble ever so slightly. From this trembling, astronomers, like doctors reading a pulse, infer the star's temperature, density, and age. But the Kepler telescope spotted an oddity: many stars that spin fast and are covered in spots show no trembling at all. It's as if they've lost their voice.

Light from a distant source passing near a neutron star bends like a flashlight beam in a funhouse mirror. Astrophysicists ran a numerical experiment: they traced rays backward from the observer to the star and looked at what picture a telescope would see.

A star 300 light-years away dances with an invisible partner. One side of the star heats up more than the other, as if the unseen dancer is breathing a hot wind onto it. This partner is a neutron star — a city-sized cinder so dense a teaspoon of its matter outweighs Mount Everest.

Scientists have described a new type of invisible star that behaves like a breathing lens. Such a star is made of ultralight boson particles (not yet discovered). Its gravity causes spacetime curvature — this is the lens, which rhythmically expands and contracts, as if breathing.

In 2019, the Event Horizon Telescope gave humanity the first image of a black hole's shadow. Since then, astrophysicists have dreamed of more: seeing how matter moves in the very funnel of spacetime. One of the mysteries is chaos.