Yi Yang

70 days. That's exactly how long the plateau, the steady glow after the blast, lasted for supernova SN 2018gj. Usually, these plateaus stretch a hundred days or more. This short plateau was the first crack in the star's mask. Images from the Hubble Space Telescope pinpointed the progenitor: a red supergiant. Enormous. Cold.

Massive stars end their lives in a grand explosion — a supernova. Their cores collapse into a neutron star (a super-dense ball where a teaspoon of matter weighs a billion tons) or a black hole. For a long time, the most common type of such outbursts was thought to be the domain of solitary stars. However, supernova SN 2018gj broke the rule.

An atomic nucleus usually lives in a single energy state, like a ball resting on the floor. But thorium-229 has a rare exception: the nucleus can get stuck on a tiny step above the floor — the so-called isomeric state. This step is so low that it can be nudged by ordinary light, not just hard radiation.

When a heavy nucleus slams into interstellar gas at enormous speed, it shatters into pieces. Those pieces (lithium, beryllium, boron) then fly onward, and their abundance in the cosmic-ray flux depends on how the breakup unfolded. Conventionally, one expected the proportions to shift smoothly with energy, like the taste of soup when you keep adding water.

A light bulb that doesn't burn out but flares brighter and brighter until it blows the whole fixture apart. That's roughly how the most massive stars in the universe die. When a star's core heats up to billions of degrees, pairs of particles (electrons and their antimatter counterparts, positrons) begin to form.

A massive star ends its life in a spectacular collapse: the core compresses into a neutron star or a black hole, while the outer layers fly off in a dazzling supernova.

You're listening to the faint whisper of stars, and nearby someone keeps moving a chair. In gravitational wave telescopes, that role is played by scattered light: it reflects off trembling surfaces and creates false signals.

The quantum world is tricky: sometimes particles confined to a flat layer and pierced by a strong magnetic field start behaving like a liquid made not of whole electrons but of their fractions — fractional charges. This is the fractional quantum Hall effect.