The Death Of a Star Ask not for whom the bell tolls, it tolls for thee

How do we “know” stars die? l ____________ reveal different types of stars. l How did they get there? l Physics tells us how stars work. l __________ depends on mass (L:M 4 ) (Gas) l Fusion principles (4 H  1 He) tell us the rate stars use energy. (kinda like MPG on a car.) l Stars will run out of ___. (the dial goes to “E”)

l Every star fights a “________”. l _______ force pulling the star together. l Fusion “_____” pushing the star apart. l Most stars find a balance. l Some stars are never balanced: l Cephids pulse as they grow larger and smaller. Fusion Gravity

Cepheus

A star’s fate is chosen at birth l The outcome of the battle is determined by ______ and _______ means

Three paths

Small Stars l Small stars last longer (don’t consume fuel as quickly) l ____________on HR diagrams. l “Burn” ________ for most of their lifetime.

Red Giants l As star runs out of hydrogen, the core _____ l Gravity starts to “win” --> _______ in core. l Increased “pressure” starts ________ fusion l 150 Million K l Carbon & Oxygen Products l ________ temperature makes outer part of star _________ yet…. l Expanded surface is actually “_______” so appears _____

Red Giants l Stars less than 1.4 Solar Masses l Gravity is _______ l Outer layers eventually “puff off” - not enough gravity l Planetary ________ forms from gas l ____________ remains

If it’s a cloud, why does it look like a ring?

Cat’s Eye: Another Planetary Nebula

White Dwarfs l Carbon/Oxygen l Matter is ___________ l One teaspoon = a pickup truck l Electron/quantum pressures balance gravity l Very Hot : 30,000K to 200,000 K l Slowly Cool to Black Dwarfs l So slow, none exist yet. l Except this guy 

White Dwarfs

Red Supergiants l Stars more than 1.4 Solar Masses l Gravitational Core Energy Reaches ___ Million K l Carbon turns to _______________ l With enough mass, even heavier elements fused l At each step, less and less energy yielded --> shorter duration l Star keeps getting ________! l _______ is the end of the road….

The most famous S-G

Fusion Layers in a Supergiant

Why Stop at Iron??

Review l ______ determines the fate of a star. l The two forces acting on a star are ____ and _____ l When a star reaches the end of its life it begins to fuse ______ and it ______. l When fusion stops a typical star will produce a __ and become a ______ _____. l Even the largest stars can’t fuse elements heavier than _____. Mass gravityfusion helium swells planetary nebula white dwarf iron

The party is over… l Once _____ is in the core, outwards pressure ceases l Core ________ at 1/4 the speed of light & takes about 1/10 of a second l Collapse of the core to about 100 km across l Outer layers “bounce” of the solid core l Releases 100x the energy of our sun produces in it’s lifetime -- in 1/10 of a second!!!

A supernova l Note the before / after differences l 1987A

After the party… l Lot’s of _________ hanging out during this explosion l Neutrons “_________” with lighter elements making heavy elements: l Calcium, Gold, Zinc, Uranium, etc… l Forget Hollywood ….. We are all stars!!!

Aftermath: l After a supernova explosion you can wind up several possibilities l Nebula & Neutron Star l Nebula & Pulsar l __________

Nebula l ________ of material left from the explosion l The “Primordial Goo” for new stars, planets, & people!

Supernova 1987 l Very complicated structure l Nearby star affecting the cloud

Our new neighbors?

Neutron star l Forms if the remaining core is between 1.4 and 3 times the ____________ l All this mass in the size of _________! l One teaspoon > The Sears Tower l All available space in the atom (which is % space) is removed.

Neutron Star

Pulsar l Neutron star that ______. l Spinning magnetic field channels radiating energy into ______. l If this beam isn’t always pointing at us - it _______ like a lighthouse. l First Pulsar was mistaken as ________ communication

A Pulsar

Black Holes l Remaining Core is more than 3x the sun. l Gravity overcomes ___________, neutrons vanish l Matter in the core overlaps : a singularity l Gravity prevents ______ from ________.--> Black Hole l Closest light can get without being trapped: “______________” l 3 S.M star = 55km E.H. (Chicago?) l Earth as a black hole? Compress it into a marble!

Finding Black Holes l May pull matter off a nearby star - Accretion Disk X- Rays l Immense mass in the center of galaxies

A trip to a black hole l Pretty Short l Difference in gravity between your head and feet literally pull you apart. l Once you hit the E.H. you aren’t coming back. l Everything you are is crushed into a single point - you no ____________ l No one would see you enter the Black Hole because time stands still at the edge.

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