fritz zwicky

An old stellar ball that has gathered hundreds of thousands of suns has been circling the edge of a dwarf galaxy for billions of years. By all calculations, it should have long ago plunged into the center like a heavy stone into jelly. But the ball holds its ground, and this fact has been nagging astrophysicists for several decades.

A light ray passing near a massive body bends around it, like a runner rounding the corner of a stadium. For a neutron star, this deflection angle is usually assumed to be the same as for a point mass. But if the star is wrapped in an invisible halo of dark matter, the picture changes: light passing through the halo is deflected less than the total mass would predict.

A gravitational wave from a black hole merger is like a bell tolling in the night. The loudness tells you how far away the source is. But to learn how fast the night itself, the cosmos, is expanding, you usually need a second signal: a flash of light or a catalog of galaxies. Both are rare to catch.

In 1929, Edwin Hubble pointed his telescope at distant galaxies and discovered they were receding. Ninety years later, two measurements of this recession rate, from ancient light and from nearby stars, stubbornly disagree. A 9% discrepancy cannot be chalked up to error. It is as if the Universe in its youth and in its maturity runs on different clocks.

In August 2019, the LIGO and Virgo detectors picked up gravitational waves from the merger of two compact objects in a binary star. One weighed 23 solar masses — a standard black hole. The other came in at 2.5–2.67 M⊙.

In cricket, there's a special delivery — the googly. The ball spins in a way that deceives the batsman. Physics had its own googly: for nearly half a century, mathematicians couldn't make twistor theory work with real gravity. It described 'nice' fields perfectly, where everything twists in one direction. But as soon as an 'awkward' component appeared, the machinery broke down.

The standard model of cosmology, based on the field equations proposed by Einstein, describes the Universe as a cocktail of dark matter (discovered thanks to Vera Rubin) and dark energy in roughly a 1:3 ratio.

Spacetime is not empty: it shivers. After the Big Bang, the universe was filled with a hum of gravitational waves, like the low rumble of a giant bell. In this ripple, as it turns out, particles of dark matter, the invisible substance that holds galaxies together, can be born. But the previous idea had a snag.

Einstein’s cosmological constant — a blunder or a boomerang insight? The universe’s acceleration caught physicists off guard: ΛCDM works, but why is the vacuum energy so absurdly tiny? Imagine an ocean heaving with quantum fluctuations, yet on the surface only a microscopic ripple.

The Universe grows like a metropolis: galaxies skyscrapers are erected on an invisible scaffold of dark matter: its gravity pulling in construction material. Meanwhile, dark energy makes the city itself continuously expand.

Drop two pebbles into a pond at the same time — the ripples will spread evenly and in sync. The same happens in a quantum interferometer: a particle is split into two waves that travel along different paths and then meet. Ideally, their crests align.

The beacon flares up and then nearly goes out, even though the lamp inside burns steadily. That is exactly what astronomers saw when they pointed their telescopes at the galaxy I Zwicky 1. At its center sits a supermassive black hole that devours gas and dust so greedily that a scorching disk forms around it, shining brighter than an entire galaxy.

A pot of boiling water bubbles and churns, mixing everything inside. Take it off the heat, and the motion subsides as the water slowly cools. The Universe is like that: right after the Big Bang, it was a searing 'soup' of particles that constantly collided and transformed into one another. But as space expanded, the cosmos cooled, and particles met each other less and less often.

Dark matter has eluded direct observation so far, even though its gravity holds galaxies together. One hypothesis: it’s made of axions — ultra-light particles predicted by theory.

At the center of our Galaxy lies a supermassive black hole, with stars orbiting around it. Their motion resembles a cosmic dance: some race along elongated orbits, others follow nearly circular paths. If invisible dark matter exists near the black hole, it slightly distorts these orbits, like an unseen hand nudging a star off course.

The night sky is full of stars, but they are only a small part of everything that exists in the universe. Astronomers have long noticed a strange thing: galaxies rotate so fast that they should fly apart, yet they don't. Something invisible holds them together, like invisible threads linking beads on a spinning wheel. This "something" was named dark matter.

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.

Dark matter is the invisible scaffold of the cosmos, its existence betrayed by whirls of galaxies to Fritz Zwicky and Vera Rubin. What it is made of remained a mystery for half a century. A new hypothesis paints an unusual picture.

Particles of dark matter can behave like molasses: in one model they don't interfere with each other; in another, they gently jostle, creating viscosity. This determines how quickly giant black holes at the centers of galaxies fall into each other and merge.

The Milky Way's stellar disk is like a glowing pinwheel, and тёмное вещество is an invisible cloud around it. For the first time, its shape has been precisely measured. Astronomers tracked the motions of millions of stars and built a 3D map of the тёмное гало out to 160,000 light-years.

The light from a distant galaxy split into two, then three, then four, and in the center a fifth ghost appeared. That is HerS-3: a young galaxy full of dust and newborn stars, whose light passed through a gravitational lens, a massive object that bends rays like a magnifying glass bends light.

Someone has thrown an invisible stone into the stellar pond of the Milky Way. The ripples spread not through water but through the motion of stars: in a region 200 by 50 parsecs across, their average vertical velocity is 7 km/s lower than that of their neighbors. The deviation is statistically significant at the 6σ level, so chance cannot explain it.