Life Cycle of a Star

Stage 1 (Nebula)Stage 1 (Nebula)• A nebula is a cloud of dust

and gas, composed primarily of hydrogen

• Birthplace of stars

Cone Nebula

Ring Nebula

Rosetta Nebula

Eagle Nebula

egg nebula in inferred

Stage 2 (Main Sequence Stage)Stage 2 (Main Sequence Stage)

• Longest stage of stars life (90%)

• Nuclear Fusion is occurring Hydrogen (H) is being converted into Helium (He)

• Stage our sun is in!

Stage 3 (Red Giant)Stage 3 (Red Giant)Massive & Super massive = Super red giantMassive & Super massive = Super red giant

• Star runs out of hydrogen and uses Helium as it fuel source.

• Helium changes into Carbon

• Grows very large / gets cooler on the surface.

Our sun

HR DiagramHR Diagram((Hertzsprung-Russell diagram)Hertzsprung-Russell diagram)

• Show relationship between luminosity (brightness) and temperature

90% of stars are Main Sequence

Our Sun

Stage 4 (nova)Stage 4 (nova)Massive & super massive = SupernovaMassive & super massive = Supernova

• Massive stars will Supernova

• Brilliant explosion• Results in a white

dwarf, pulsar, or black hole depending on mass of star.

Crab Nebula – went supernova in 1054

End Stage of a massive starEnd Stage of a massive star(Neutron Star/Pulsar)(Neutron Star/Pulsar)

• A star at least 2X more massive than our sun collapsed into a space the size of a small city.

• So dense a teaspoon of a neutron star would weight more than a cruise ship full of people.

http://library.thinkquest.org/25763/lsupernova.htm

X-ray

Crab Nebula containing a Neutron StarWent Supernova in 1054

End Stage Super Massive Star End Stage Super Massive Star (Black Hole)(Black Hole)

• Only occurs with very massive stars (3+ times the mass of our sun)

Our Sun’s fate

• After main sequence, stages differ!!!!!

• Our sun is not massive enough to become a black hole or a neutron star. After it becomes a red giant it will Nova and form a …

Planetary Nebula

White Dwarf

White Dwarf

White Dwarf

• The White Dwarf will burn very hot (Up to 20,000 degrees Kelvin).

• Eventually it will burn out and become a Black DwarfBlack Dwarf.

HR - DiagramHR - Diagram

Important Stars

http://seds.org/messier/

Constellation – A pattern created by stars.• Orion

– Stars:• Betelgeuse

– (red supergiant)

• Rigel – (blue giant)

Not all stars: Nebulas

The Brightest Star: SiriusSirius(Not including the sun)