The Life Cycle of Stars

Stars begin in nebulae, vast clouds of gas and dust. When a region becomes dense enough, gravity pulls material in, igniting nuclear fusion. This process creates a protostar, embryonic and enshrouded in a cocoon of dust.

Stars spend most of their life in the main sequence, fusing hydrogen into helium. The Sun, a G-type main-sequence star, has been stable for 4.6 billion years. This phase lasts until hydrogen in the core is exhausted.

As hydrogen depletes, stars expand into red giants. Did you know? Sun-like stars grow so large they can engulf their closest planets. Helium fusion begins, but this phase is shorter and more volatile than the main sequence.

Massive stars culminate their lives in supernovae, outshining entire galaxies momentarily. The explosion distributes elements across the cosmos, seeding future stars and planets. It's a cosmic recycling program, with each generation of stars contributing to the next.

After a supernova, the core collapses. For stars up to three times the Sun's mass, this results in neutron stars, the densest stars known. More massive stars collapse into black holes, from which not even light escapes.

Less massive stars, like the Sun, shed outer layers gently, creating planetary nebulae. These stunning structures glow with complex shapes and colors, forming from ionized gas. They are short-lived on a cosmic timescale, dispersing within tens of thousands of years.

The remnants of low to medium mass stars, white dwarfs are Earth-sized but incredibly dense. They don't have fusion reactions, slowly cooling over billions of years. Some may become black dwarfs—cold, dark remnants that emit no light.

Some white dwarfs crystallize entirely, becoming cosmic diamonds. The largest known is BPM 37093, nicknamed 'Lucy' after the Beatles' song.