How old is the solar system? 4.6 billion year birth
The solar system formed 4.6 billion years ago from a collapsing cloud, dated by meteorites and Moon rocks with matching ages.
A cloud collapsed and lit the Sun
About 4.6 billion years ago a gas cloud 65 light years wide collapsed after nearby supernova shockwaves. Gravity heated the core to 15 million degrees until hydrogen fused, lighting the Sun that holds 99.8 percent of system mass today.
Leftover gas and dust flattened into a disk 200 astronomical units wide where planets grew in 10 to 100 million years. Inner rocks built Mercury to Mars in hot zone, while outer ice giants gathered hydrogen beyond frost line at 5 astronomical units.
Jupiter guarded and meteorites prove the age
Jupiter formed first within 4 million years and blocked inward drift, shielding Earth from collisions. Without its gravity inner planets might spiral or suffer ten times more impacts, as computer models show 90 percent of comets get ejected by giant.
Oldest meteorites date 4.568 billion years with lead isotopes, matching oldest Earth zircons at 4.4 billion years. Moon rocks from Apollo missions read 4.5 billion years, giving three independent clocks that all point to same 4.6 billion birthday.
- Age: 4.6 billion years, cloud 65 light years
- Sun holds 99.8 percent of mass, core 15 million degrees
- Planets built in 10 to 100 million years
- Jupiter formed in 4 million years, ejected 90 percent comets
- Meteorites 4.568 billion years, zircons 4.4 billion years