Stellar astro-ph.SR

A swing pushed once per second usually oscillates once per second. But if you push it harder and at the right rhythm, it can swing three times slower: one full swing for every three pushes. Physicists call this subharmonic resonance, and it seems to govern the most prominent climate and solar oscillations.

Over the tropical Pacific, air pressure breathes with periods from two to fourteen years. The barometer on Tahiti rises while it falls in Darwin, Australia, and the entire planet's climate shudders: El Niño arrives. Meteorologists call this the Southern Oscillation and have tracked it for 138 years, but until now they couldn't answer a simple question: where do such periods come from?

Place two pendulums side by side and give one a gentle push; the other will soon pick up the rhythm. This behavior isn't limited to clocks on a shared shelf; it also applies to the plasma inside the Sun. In the star's convection zone, two huge ring-shaped flows circulate: one closer to the surface, the other deeper. Each oscillates with its own period—12.05 and 9.52 years.

The RATAN-600 radio telescope is a ring of hundreds of aluminum panels on a mountainside in Karachay-Cherkessia. In the spring of 2018, its mirror caught radio waves from sixteen red dwarfs — small, dim, but very long-lived stars.

North of the microquasar SS 433, an arc has emerged in the soft X-ray band. Faint and diffuse, yet stubbornly tracing contours already familiar from radio observations. Astronomers studied its spectrum and saw gas heated to eleven million kelvin. Gas that could not have been heated by the jets or the accretion disk wind.

The Solar System takes 210 million years to complete one orbit around the center of the Milky Way. The last time we were on this same side of the Galaxy, early dinosaurs were roaming the Earth. That number, 243.72 km/s, has now been refined thanks to rare stars that streak through the Galaxy like cannonballs.

In Euclid's deep fields, stars flare up that were not in any catalog. A telescope built to map dark matter has worked like a camera trap: one frame, and a cosmic explosion is already on record.

At the center of the supernova remnant SN 1987A, 168,000 light-years from Earth, hides an object that astronomers have been seeking for 37 years. This is the closest supernova to have exploded in front of modern telescopes, and the only one where the compact remnant has yet to be seen directly.

In August 2024, the MIRI coronagraph on the James Webb Space Telescope stared at Alpha Centauri A, the nearest Sun-like star to our Sun. At 1.5 arcseconds from the star, a point source, S1, blinked into view. Flux: 3.5 mJy, contrast: 5.5×10⁻⁵. Four to six sigma. A lighthouse flashing in the fog.

Three bodies attracting each other by universal gravitation: a problem that has stumped mathematics for three centuries. After Poincaré, it became clear that no general solution exists and trajectories are chaotic. But within this chaos there are islands of order: periodic orbits where motion repeats.

Deep inside a molecular cloud, where temperatures drop to 10–20 kelvin and gas densities reach a million particles per cubic centimeter, a frozen shadow prevails. There, far from starlight, water, carbon dioxide, and other molecules freeze onto dust grains.

Four hours and fifty-eight minutes. With a rhythm like a metronome, something passes in front of the white dwarf ZTF J1944+4557, dimming its light by a third, sometimes almost by half.

A wind blowing against the planet's rotation stokes a carbon forge. That is what the atmosphere of PSR J2322-2650b looks like: a Jupiter-like companion to a millisecond pulsar.

In the dark cloud NGC 6334I-North, 5500 light-years from Earth, the ALMA radio interferometer spotted something unexpected: around a young massive star, a disk of gas and dust is swirling, and inside it are seven dense clumps. Each one could become a star. This is what the birth of a stellar family looks like, and an unusually large one at that.

On the night of March 9–10, 2024, a cloud of plasma ejected by the Sun raced away from the star. It had already passed a distance of five solar radii when a ground-based array of 352 antennas in California's Owens Valley caught a brief radio signal from it.

In the dense swarm of old stars known as the globular cluster M15, astronomers have spotted not just stars but layers of time. Some stars were born earlier, others later, and their chemical composition reveals their origin with the precision of an archaeologist reading the strata of an ancient settlement.

Brown dwarfs are objects that sit between planets and stars: they are more massive than planets but not heavy enough to sustain stable fusion in their cores.

The TESS telescope, usually hunting for planets around other stars, spotted 24 dimmings around RZ Psc. These were comets — chunks ranging from 1 to 7 km in size, transiting the star's disk. Like a distant searchlight momentarily blocked by a tiny pebble: the deeper the shadow, the larger the object.

Imagine a bridge with its middle ripped out: cars on the other side would be a surprise. That's how astronomers long viewed black holes with masses from 50 to 130 solar masses: the stars that could produce them explode as pair-instability supernovae.

In the vast darkness of interstellar space, the rogue planet WISE 0855 flickers with a barely perceptible heat glow, like a cooling ember. Its temperature is only a few dozen degrees above freezing — if life existed there, it would see a sunless sky, in an eternal icy haze.

The planet's gravity rhythmically squeezes and kneads the moon like dough: from this constant 'kneading', the interior heats up, and oceans of water can persist under the icy crust for ages. In the Galaxy, there are plenty of rogue planets, thrown out by supernova explosions.

The Universe is filled with invisible mass, dark matter, which reveals itself only through gravity. One hypothesis suggests that dark matter consists of primordial black holes — objects formed in the extreme conditions just after the Big Bang.

Brown dwarfs are heavier than planets but lighter than stars. Their atmospheres resemble a bubbling pot: clouds of scorching sand and iron droplets rise and fall.

The second interstellar guest, comet 3I/ATLAS, shines unusually due to rusting metal grains in its icy core. As it gets closer to the Sun, it behaves like an old tin can tossed into a fire: the heat melts the ice, water seeps into the metal, and vigorous corrosion begins.

Far beyond the Solar System, a world called VHS 1256B wanders — a giant planet without a star. For a long time, astronomers couldn’t figure out why its brightness jumped by nearly 40% in just a few days. The answer came with the James Webb telescope: it turns out, colossal storms of silicate dust engulf the entire planet.

The Sun is not just a ball — it's a magnetic mansion. Its invisible force lines, like electrical wiring, thread through space and control space weather. But until now, we've only seen this wiring from the landing — the plane of Earth's orbit. The attic and basement, the magnetic poles, remained a mystery.

Just as yeast turns flour into fluffy dough, radioactive 'seasoning' from a supernova — the explosion of a massive star at the end of its life helps mold a rocky planet. The key ingredient here is aluminum-26, a radioactive isotope that releases heat as it decays.

The solar wind isn't a calm stream but a bubbling soup of charged particles. Diving close to the Sun, the Parker probe picked up two types of stirring waves. Left-handed ones, like a whisk in a chef's hand, whip up the material when the temperature differs along and across the flow.

In the darkness of interstellar space drift millions of rogue planets — worlds not bound to any star. They are almost impossible to see, but when such a wanderer passes in front of a distant star, its gravity bends the light and momentarily creates a cosmic magnifying glass.

The James Webb Space Telescope is watching TRAPPIST-1—a tiny red dwarf with seven Earth-sized planets in orbit. And it sees something unusual: bright flares on this star barely reach 3500–4000 degrees. For comparison, a typical solar flare heats up to 9000–10000 degrees.

Betelgeuse is a giant star ready to explode as a supernova. But it may not be alone: a small companion star, Sivarkha, circles in a tight orbit. Every 2000 days, it plunges through Betelgeuse’s outer layers, like a boat cutting through water, leaving waves of superheated gas.

In three binary systems, a white dwarf, the dead core of a star, steals gas from its companion. The companion is so dim that it cannot be seen with an ordinary telescope. The James Webb Space Telescope looked at these pairs in infrared light, like a night-vision camera.

The Sun’s gravity creates an invisible goblet, in which dark matter of a special kind — ultralight — doesn’t splash around chaotically, but occupies strict energy steps, like transparent layers of liquid. So around the Sun, a natural spectroscope emerges, sorting the invisible substance into levels, just like electrons in an atom.

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.

In 2019, Betelgeuse suddenly dimmed, sparking rumors of an imminent explosion. But clouds of cosmic dust turned out to be the culprit. Now, the Gemini North telescope has discerned a minuscule companion star in its dazzling glare, just as calculations had predicted.

At the centers of many galaxies lurk supermassive black holes, surrounded by disks of gas, cosmic dust, and stars. Their collisions can spawn gravitational waves — ripples in spacetime.

A star trembles like a bell after being struck. These tremors, tiny fluctuations in brightness and surface, can be caught by a telescope. From the frequencies of these 'stellar notes,' astronomers infer what's happening inside: how old the star is, how it's structured.

In Andromeda's stellar stream, a long ribbon of stars ripped from a small galaxy during a collision with a larger one, astronomers spotted a star that outshines all its neighbors. It pulsates, swelling and contracting every 89 days, like a heart beating in rhythm. Such stars are called Type II Cepheids, and this one is the brightest known.

The Sun doesn't rotate as a solid body: its equator spins faster than its poles. This difference in rotation speed creates layers that move at different speeds, like ocean currents at different depths.

In a hot gas of charged particles — plasma — chaotic electric fields work like a sieve. A slow particle gets surrounded by a cloud of opposite charges, which cancels the external field. A fast one sheds this armor and gets accelerated.