solar neutrino

The atomic nucleus is usually pictured as a dense ball where protons and neutrons are mixed together. But in some isotopes, neutrons can stick out far beyond this ball, forming a diffuse shell — a neutron halo. This is especially common in nuclei with many more neutrons than protons.

A spinning top whirls so fast that the air around it starts to rotate in unison. A black hole behaves in much the same way: if it spins, it can transfer its energy to particles that happen to be nearby. This process is called superradiance: it's like an echo in the mountains, but instead of sound, new particles are born.

In the distant Cigar Galaxy, there is an unusual beacon. It doesn't shine in the usual sense: its rays are born in a scorching cloud around a black hole that is devouring matter from a companion star. Such objects are called ultraluminous X-ray sources. Their X-ray brilliance is so intense that it outshines entire galaxies. This cloud, the corona, is like a boiling cauldron.

Solar neutrinos are tiny particles born in the Sun's core by the trillions every second. They pass through Earth almost without noticing it, and for a long time they were considered absolutely stable. But perhaps they too can "age"—decaying imperceptibly, vanishing on their way to us.

Erwin Schrödinger pondered how life maintains order despite the second law of thermodynamics. He could never have imagined that part of the answer lies hidden in the instability of giant stars.

The Sun is a giant nuclear reactor that continuously sends us light and heat. But it also has another, almost silent postal service: every second, tens of billions of neutrinos, ghostly particles born in the thermonuclear furnace, fly through a square centimeter of your palm. Most of them leave no trace.

Dark matter detectors are essentially incredibly sensitive microphones, capable of hearing a whisper amid the roar of a rock concert. Their job is to catch the rare nudges from hypothetical dark matter particles, which are thought to occasionally collide with atomic nuclei of ordinary matter.

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.

Tiny invisible bullets pass straight through the Sun, barely noticing its matter. These are axions — hypothetical particles so light and elusive that they are often compared to ghosts.

A pool of the purest water, into which tiny, almost invisible droplets occasionally fall. Each leaves a barely perceptible ripple, and capturing it requires years of patience. That is what the hunt for solar neutrinos looks like in the DEAP-3600 detector — a huge vat of liquid argon hidden deep underground.

Colliding two lead nuclei at the Large Hadron Collider is like throwing two hefty bags of marbles at each other. Usually, the marbles scatter in all directions, but sometimes one bag passes so close that the marbles don't collide: they just exchange glances.

Deep beneath the Apennine Mountains, in a tank holding three tons of liquid xenon, something gives a barely perceptible shudder every few days. It's a solar neutrino, a ghostly particle born in the Sun's thermonuclear furnace, that has traveled 150 million kilometers through empty space and solid rock to finally collide with a xenon nucleus.

A thin crystal of hexagonal boron nitride is a relative of graphite, but transparent and insulating. Occasionally, single defects appear in its lattice: a boron or nitrogen atom is missing, leaving a trap for electrons. Such a trap can absorb light and re-emit it, like a tiny flashlight.

Dark matter is the invisible framework of the Universe. It doesn't emit light, but its gravity keeps galaxies from flying apart. A new hypothesis: dark matter consists of dark photons — ghostly particles that are invisible under ordinary conditions.

Ultracold atoms can act as one. When a neutrino is born inside such a cloud, it usually slips away unnoticed.