Birth and Death of Stars The Life Cycle of Stars 28.3 page 628 : http://outreach.physics.utah.edu/Labs/StarLife/starlife_main.html

The Hertzsprung-Russell diagram isn’t just an orginazational chart for the the stars, but the life cycle of the stars!

Life Cycle of Stars

http://mail.colonial.net/~hkaiter/life_cycle_of_a_star.htm

Stellar Careers The lives of the stars seem to be “predestined” The MASS of a star determines … what type of star it will be, where it will be on the main sequence, and how long it will live for. What it will end up as at its death Each type of star has a particular series of events during their lifetime. Deaths can be spectacular!

The MASS of a star determines … what it will be

Stage 1 Nebula The space between stars is filled with gas and dust. called a nebula 99% of interstellar matter is hydrogen. Temperature: Cool Eventually gas “clumps” and compress

Life Cycle of a Star Death/old young nebula

Whatever the cause, the nebula begins to contract. As the nebula collapses, the temperature and density increase. As it contracts, it breaks into many clumps, which forms hundreds of stars of various masses. The size of each clump determines the mass of the star that will form.

Joseph Howard

Clumps / fragmentation These will become STARS

Stage 2 Protostar Still shrinking, getting denser Temperatures increase Core is contracting Recognizable as a ‘star’ Has a photosphere surface

Life Cycle of a Star Death/old young protostar nebula

“Duds” or Failed Stars Clumps without enough mass are too small to become stars They just cool and compact to become brown dwarfs orbiting in space Gas Giant planet Jupiter is a failed star.

Life Cycle of a Star Not enough mass to reach temps to fuse hydrogen Death/old young Brown dwarf protostar nebula Not enough mass to reach temps to fuse hydrogen “dud” Gas giant planet: Jupiter

IF the protostar has enough temperature and luminosity to make it onto the H-R scale. Its mass determines where it jumps on. http://outreach.physics.utah.edu/labs/star_life/support/HR_animated_real.html

Stage 3 A Star is Born! When the core reaches 10,000,000 K Nuclear FUSION begins Hydrogen fuel is fusing into helium A true star

Life Cycle of a Star fuse hydrogen fuel 100 billion yrs. Main sequence Death/old young Brown dwarf protostar nebula Not enough mass to reach temps for fusion of hydrogen Gas giant planet: Jupiter Main sequence star fuse hydrogen fuel 100 billion yrs.

Main Sequence, Hydrogen is fusing into helium A star spends 90% of it’s life as a main sequence star. This is it’s mature, adult stage. Our Sun will be here for 10 billion years

Main Sequence at Last It reaches Equilibrium: its stable The heat & pressure of the gas expanding outward balances the GRAVITY that is pulling the matter inward

Death of a Star

Life Span Massive stars use up their fuel faster, so they spend less than a 1 billion years as a main sequence The smaller mass stars spend 100 billions years as a main sequence star!

Life Cycle of a Star Death/old young Brown dwarf protostar nebula Not enough mass to reach temps for fusion of hydrogen Gas giant planet: Jupiter” Main sequence star 100 billion yrs. white dwarf black dwarf Fusing hydrogen for fuel

Stage 4: Running on Empty Star is aging, hydrogen fuel is used up, and helium is building up in the core. There is no heat to push out so gravity pushes in, the core becomes unbalanced and begins to collapse As it collapses, temperature increase until it reaches 100,000,000 K! Helium begins to fuse. Heat generated in the core, It EXPANDS

The outer layers are expanding and cooling It is now a RED GIANT Star begins leaving the main sequence

Leaving the Main Sequence It’s a RED GIANT It is cooler, but bigger, so it’s brighter

Stage 5 Planetary Nebula Core continues fusion of helium. When helium fuel is gone, the core shrinks Outer gas layers are thrown-off as a Planetary Nebula Example: Planetary Nebula IC 418

Stage 6: The End Red Giant All that is left is the core White Dwarf

White Dwarf All that’s left is the core: very small (earth size), very dense (200 x’s more dense than Earth!), very HOT (100,000 K) core It will slowly cool over a billion years.

Life Cycle of a Star Death/old young Brown dwarf protostar nebula Not enough mass to reach temps for fusion of hydrogen “dud” Main sequence white dwarf black dwarf Fusing hydrogen for fuel Red giant planetary white dwarf Black 10 billion yrs nebula dwarf Hydrogen fuel fusing helium fusing Main sequence

Red Super Giants Example: Betelgeuse When the helium is fusing, temps increase, it expands, and becomes a super red giant and cools Gravity contracts the core until its heated enough to begin burning the next element, carbon. This process continues through the fusing of oxygen, neon, nickel, and silicon with the high mass star alternating between the blue giant phase and the red giant phase throughout. Large stars repeat this expansion and contraction cycle up to 7 times as their core elements keep fusing until they reach iron. When the core becomes iron fusion ends Example: Betelgeuse

Supernova VERY MASSIVE stars: > 8 M Supernova remnant Supernova VERY MASSIVE stars: > 8 M When core collapses, density reaches astonishing 400,000,000,000,000 g/cm3 The core ‘overshoots’ its equilibrium point and rapidly ‘rebounds’ Core explodes in a high speed shockwave, blasting everything into space! Crab Nebula, remnant of a supernova that exploded in 1054 A.D. http://www.maniacworld.com/Crab-Supernova-Explosion.html https://www.youtube.com/watch?v=9D05ej8u-gU most astounding fact

Final Stage for Massive Stars (Neutron Star or Black Hole) Stars less than 8 solar masses become dwarf stars (cool, dim, burnt out) Stars 8 solar masses or greater become neutron stars or black holes Neutron Star Black Hole

Neutron Star When the iron core of a MASSIVE STAR is collapsing, it might stop. Leaving behind an extremely small, dense neutron star. Extreme density 1018 kg/m3 Extremely small: size of a city Spin! Can emit a beam and pulse: Pulsar

Life Cycle of a Star Death/old young Brown dwarf protostar nebula Not enough mass to reach temps for fusion of hydrogen Gas planet Jupiter Main sequence 100 billion yrs white dwarf black dwarf Fusing hydrogen for fuel Red giant planetary white dwarf black 10 billion yrs nebula dwarf Hydrogen fuel fusing helium fusing Main sequence Neutron Star Black hole Main sequence Super red Supernova! 2-100 million yrs. giant Hydrogen – helium – carbon- neon – oxygen - silicon …

The END - Death Stars iMovie Name of final object Starting Mass Time / Age / years Description Picture / Image Name of a familiar star as an example