Gravity is the architect. Given enough hydrogen in one place, gravity pulls it together until the core reaches 15 million Kelvin and nuclear fusion ignites. A star is born. For millions to billions of years, the outward pressure of fusion holds gravity at bay. When the fuel runs out, gravity wins. What follows, white dwarf, neutron star, or black hole, depends entirely on how much mass was there to begin with.
This is the stars and planets layer: the astrophysics of how gravity and nuclear physics create the large structures of the universe. Stars, stellar remnants, black holes, neutron stars, galaxy-scale dynamics, and the planets and moons that form around stars. It is also the layer where specific exoplanet discoveries live: the individual worlds we have found that might, or might not, harbor life.
The core questions at this scale
- What happens to a star when it dies, and does the answer depend on its mass?
- What are black holes, really, and how do we observe something that emits no light?
- How did Earth-like conditions arise around so many different stars?
- What do gravitational waves tell us about collisions we cannot see?
- Are there planets beyond our solar system with conditions suitable for life?
Stellar remnants and extreme objects
- Types of Black Holes, stellar-mass, supermassive, and primordial
- How Black Holes Form, the stellar collapse process in detail
- Neutron Stars Explained, the densest stable objects in the universe
- Magnetars Explained, neutron stars with the strongest magnetic fields known
- White Dwarf Stars, the quiet end state of most stars
- What Is a Quasar?, supermassive black holes at their most active
- Gravitational Waves, ripples in spacetime from colliding massive objects
The Milky Way and beyond
- The Milky Way Galaxy, our home galaxy in context
- Cosmic Rays Explained, high-energy particles accelerated by extreme events
- The Oort Cloud, the distant shell of comets at the edge of our solar system
Exoplanets: specific worlds
The site covers dozens of specific exoplanet discoveries in detail: from Kepler-22b to TRAPPIST-1d to LHS 1140 b. These are at How Scientists Detect Exoplanets. The most astrobiologically significant worlds connect directly to the Life layer below.
← Layer above: Matter, the particles and forces that make stars possible → Layer below: Life, where planetary chemistry becomes biology