The Life of a Star The Life of a Star The Life of a Star

Interstellar Gas Cloud General Composition: 71% Hydrogen, 27% Helium, & 2% other How does a cloud start forming a star? Low temperature = low pressure (pushing out) Leads to gravity being able to collapse the cloud into smaller, warmer, dense clumps

Protostar Stage Clumps to Baby star? As the gas gets pulled in by gravity, a large flat disk with a dense core at the center starts to form Forms in the infrared & radio Form in groups = similar age Protostar Stage

Mass Determines Temperature More mass = more gravity = higher pressure = higher temperatures Mass Determines Temperature

A star’s life is determined by how much mass it has Low mass stars = under 10 solar masses High mass stars = over 10 solar masses 1 solar mass = 1 sun Mass is Key

Structure of High vs. Low Mass Stars Triple Alpha Process: H He High Mass Stars CNO cycle: Passes the triple alpha process and moves on to heavier elements like CNO Structure of High vs. Low Mass Stars

You need: 1 cup with 6 marshmallows, a napkin, and 5 pasta noodles Fusion Demo!

What is that? Nucleosynthesis: formation of heavy elements by nuclear burning process As temperature increases in the core, heavier elements are fused forming layers of elements Iron – 1 billion K Nucleosynthesis

Pressure from the formation of new elements presses out while gravity is pushing in Once gravity wins the star dies Gravity is everything Importance of Gravity

Once the protostar (baby star) develops H & He fuse forming a main sequence star (yellow dwarf) – like our sun Once most of the H is fused – gravity wins – the star contracts (gets smaller), increasing the temperature, allowing the star to fuse more He – increasing the pressure – making the star expand to a much larger, cooler size – a red giant Once that He is used – fuel runs out – star dissolves into space forming a planetary nebula This leaves behind the bare core – a white dwarf Low Mass Stars

Once the protostar (baby star) develops H, He, and heavier elements fuse forming a giant star Once most of the elements are fused – gravity wins – the star contracts (gets smaller), increasing the temperature, allowing the star to fuse even heavier elements – increasing the pressure – making the star expand to a much larger, cooler size – a red super giant Once that fuel runs out – gravity causes the star to collapse on its iron core causing a supernova – leaving behind either a black hole or a neutron star High Mass Star

Under 10 solar masses Over 10 solar masses Importance of Gravity Over 10 solar masses