Luciano Rezzolla

A homogeneous dust sphere begins to contract under its own gravity. Inside it, like a rescue bubble, a region of negative pressure inflates: the de Sitter bubble. It expands, slows down near the very edge of the fall, and freezes at the Schwarzschild radius.

The collision of two neutron stars is a strike heard across the universe. Gravitational wave detectors pick up the ripples in spacetime, but the most interesting sound begins after the impact: the merger remnant, a rapidly spinning hypermassive neutron star, continues to vibrate, emitting waves for a few more…

In 2019, astronomers unveiled the first-ever image of a black hole's shadow — a dark void encircled by a lopsided orange ring. This is the supermassive black hole at the heart of galaxy M87, 55 million light-years away. The ring isn't just glowing: one side is noticeably brighter than the other, like a campfire burning unevenly, with flames leaping higher on one side.

Near black holes and neutron stars, plasma churns like water in a boiling kettle. But this 'kettle' has no walls — only magnetic fields that twist and tear. At the tears, thin sheets form where magnetic field lines reconnect, giving particles a kick like a surfer catching a wave.

At the center of the Milky Way lies the supermassive black hole Sagittarius A*. It is four million times more massive than the Sun, but by cosmic standards it behaves quietly: it only occasionally flares up when it swallows a clump of gas.

In April 2021, the antennas of the Event Horizon Telescope (EHT)—a global network of millimeter-wave radio telescopes — zeroed in on a tiny spot in the constellation Virgo.

Three milliseconds before the merger. A gargantuan black hole spinning at breakneck speed drags in a neutron star — a ball the size of a city but with 1.5 times the Sun's mass. Tidal forces stretch the star into a thread as thin as a needle and fling its matter outward.