Chapter 15 Section 3 Lives of Stars

How do stars begin? Nebula cloud of dust and gas in space Nebular begins to spin and create a gravitational field It heats up and contracts Protostar So when does it become a star? Gas and dust becomes very dense Nuclear Fusion begins!

How long does a star live? More Mass = Shorter Life Burns fuel much faster! Life span is millions of years Less Mass = Longer Life Burns fuel much slower! Life span is up to 200 billion years Example: Our Sun Medium-mass Star Approx. 10 billion years

What happens next? Medium-mass stars  Red Giant Star begins expanding Helium core collapses High-mass stars  Super Giant Star continues to expand Heat from the core makes more nuclear fusion reactions Both Red Giants and Super Giants are very bright, cooler than main sequence stars and unstable.

(Send a private message to a classmate!) How do stars die? Remember. . . What is the energy source for stars? (Send a private message to a classmate!)

How do stars die? A star runs out of fuel! Nuclear fusion ends One of three outcomes: White Dwarf Neutron Star Black Hole

Planetary Nebulas As a red giant is nearing the end of it’s life span Parts of the star can escape and float off into space Cat’s Eye Nebula

White Dwarf Blue-White Core Left over after planetary nebula escapes Half the size of Earth Very dense Faint blow for billions of years

Supernova High-mass star Bright, hot supergiants Runs out of fuel and suddenly explodes! Large masses of gas and dust are flung into space.

Neutron Star Material left over from a supernova Smaller, denser than white dwarfs Size of a city Strong Magnetic Field

Pulsars Spinning neutron star PULsating RAdio Sources Emits constant beam of radiation Can rotate up to hundreds of times per second

Black Holes An object with gravity so strong that even light can’t escape it! Created by most massive stars Can’t be see, but only speculated

Create a Star Flow Chart! Map out the life stages of a star Use paint, whiteboards, word, or any program to draw a flow chart about the life cycle of a star. Use images from these slides or the internet/ Make sure to include outcomes for low, medium, and high mass stars. Briefly describe how or why the start changes states.