Solar System
The Solar System is the Sun together with everything held by its gravity: eight planets, nine recognised dwarf planets, more than 400 known moons, and countless asteroids, comets and Kuiper-belt objects. It formed about 4.6 billion years ago from a collapsing cloud of gas and dust. The Sun holds 99.86% of the system's mass; almost all the rest is in Jupiter. Its edge can be drawn at the heliopause (~123 AU, where the solar wind meets interstellar space) or, far beyond, at the Oort cloud.
Key facts
Science
Classification
- Central star
- The Sun — a G2V yellow dwarf
- Type
- Single-star planetary system
Members
- Planets
- 8 · Mercury outward to Neptune
- Dwarf planets
- 9 recognised · Ceres, Pluto, Eris, Haumea, Makemake, and more
- Moons
- 400+ known
- Small bodies
- Millions · asteroids, comets and Kuiper-belt objects
Scale
- Age
- ~4.6 billion years
- The Sun's share of the mass
- 99.86% · Jupiter holds most of what remains
- Extent
- Heliopause ~123 AU; the Oort cloud may reach ~100,000 AU
Discovery & history
- Name
- 'Solar System' — the system of the Sun (Latin Sol) and the worlds gravitationally bound to it.
That the Sun, not the Earth, sits at the center was argued by Nicolaus Copernicus in 1543, supported by Galileo's telescopic discoveries, and given precise form by Kepler's laws (1609–1619) and Newton's gravity (1687). Uranus (1781), Neptune (1846) and Pluto (1930) extended its bounds; the 2000s brought a wave of dwarf planets and, in 2006, the definition that now counts eight planets and nine dwarf planets.
Images
Images from open archives · credit shown per image