The Sun and Solar System form

What happened

About 4.6 billion years ago, a giant, slowly spinning cloud of gas and dust called the solar nebula began to collapse under its own gravity. Most of the material fell inward and piled up at the center until it grew dense and hot enough to ignite as the Sun, which NASA describes as a yellow dwarf star, a hot glowing ball of hydrogen and helium about 4.5 billion years old. The leftover material spread into a disk around the new star, and out of that disk the planets, moons, asteroids, and comets slowly assembled.

How we know

NASA's facts on the Sun give its formation date of about 4.6 billion years ago, describe the collapse of the solar nebula, and identify the Sun as a yellow dwarf made mostly of hydrogen and helium.

Sources

• NASA. Our Sun: facts (NASA Science) (2024) · Reputable sourcescience.nasa.gov · The domain "science.nasa.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
• Evidence from stable isotopes and 10Be for Solar System formation triggered by a low-mass supernova (Nature Communications, via PubMed Central) (2016) · Peer-reviewed (author-declared)pmc.ncbi.nlm.nih.gov · Cited as a "journal" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)