Star Formation CH. 5

Stars form in vast clouds of gas and dust called nebulae Gas Singular – nebula Gas Mostly hydrogen Some helium Small amounts of iron, magnesium, silicon, oxygen, nitrogen Small amounts of more complex molecules like H2O Dust Small grains containing carbon and various silicates Complex organic molecules including various hydrocarbons

Small regions within a nebula will begin to condense and collapse due to gravity Once these regions begin to collapse, they rotate and flatten out into a disk shape with a bulge at the center This disk is called a protoplanetary disk The bulge at the center is called a protostar Within the disk, small objects collide and stick together, eventually forming larger bodies This process, called accretion, eventually gives rise to planets, moons, and other bodies

Asteroids, meteors, and comets are leftover material from the formation of the Solar System Studying them provides insight into the Solar System’s origins Radioactive dating of this material suggests that the formation of the Solar System was completed around 4.6 billion years old