Star Formation Step by Step

Every star in the night sky went through this process:

• A molecular cloud is disturbed and begins gravitational collapse
• The collapsing material forms a spinning disk with a hot protostar at the center
• Jets of material blast from the poles as the protostar grows
• When the core hits 10 million Kelvin, hydrogen fusion ignites
• Outward radiation pressure balances gravity and the star stabilizes

If the fragment holds less than 0.08 solar masses, fusion never ignites and it becomes a brown dwarf. Stars form in clusters — the Sun likely had thousands of sibling stars that have since scattered across the galaxy.