The Most Dangerous Matter in the Universe

Neutron stars are some of the densest and most compact objects in the universe. With a mass of about 1.3 to 2.1 solar masses packed into a radius of just 10 to 12 kilometers, they push matter to its limits. But their interiors might be even stranger—and potentially more dangerous. Some researchers hypothesize that at their hearts, a substance called strange matter could exist, capable of infecting and transforming anything it touches.

The Universe's Ice-Nine

Kurt Vonnegut's novel Cat's Cradle is a classic of science fiction that no bookshelf should be without. Technology, free will, religion—Vonnegut leaves no stone unturned. But one element stands above the rest: ice-nine. This alternative form of water is solid at room temperature and has the disturbing property of turning any ordinary water it contacts into more ice-nine. I won't spoil the consequences, but you can imagine the devastation if such a substance were set loose. Some scientists believe a similar phenomenon could occur inside neutron stars. Welcome to strange matter.

(Editor's note: The video has Spanish subtitles, don't forget!)

How Strange Matter Takes Over

Once again, the folks at Kurzgesagt are responsible for brilliantly presenting and explaining strange matter, though they admit it's a complex topic and they had to take some shortcuts. In loose terms, a neutron star is what remains after a giant star goes supernova. The core collapses in on itself, leading to a battle between gravity and neutrons. If gravity wins, you get a black hole; otherwise, a neutron star is born—with twice the mass of the Sun and the diameter of a city. Conditions inside a neutron star are so extreme that neutrons might become “deconfined,” forming a quark star. If the pressure inside that quark star is high enough, the strange quark could gain ground and multiply, transforming other quarks into strange quarks.

The Hypothetical Threat

That gives us strange matter, the stellar ice-nine. Indestructible, incredibly stable, and mind-bogglingly dense, nothing prevents strange matter from existing outside a neutron star. In other words, the last thing we need is a rain of strange matter particles converting protons and neutrons into more strange matter. As long as it stays inside neutron stars, we're fine... but. Yes, there's a “but.” If two neutron stars collide, they could release small amounts of strange matter—strangelets. If they touched a planet or a star, they would convert it without pause. However, strangelets (like strange matter itself) are hypothetical. Nothing has happened in the last billions of years, and the situation probably won't change... (?)