star life cycle
DESCRIPTION
Star Life Cycle. Fill in the chart when you see a yellow star. Take notes on the stars and events as well. . STARS. All stars begin the same way, but the last stages of life depend on it’s mass. The birth place of stars are Nebulas, often referred to as “stellar nurseries”. - PowerPoint PPT PresentationTRANSCRIPT
Fill in the chart when you see a yellow star.
Take notes on the stars and events as well.
Star Life Cycle
All stars begin the same way, but the last stages of life depend on it’s mass.
The birth place of stars are Nebulas, often referred to as “stellar nurseries”. Nebulas are clouds of dust and gas.
STARS
Emission: emit radiation, usually appear redReflection: reflect light of nearby star, usually appear blue.Dark: block light, appear black.
3 TYPES OF NEBULAE
Dark Nebula
Horsehead Nebula (Orion Constellation)
Reflection Nebula
Tarantula Nebula
Iris Nebula
Veil Nebula
Lagoon Nebula
Witch Head Nebula
Witch Broom Nebula
Bubble Nebula
Trifid Nebula
Gravitational attraction causes gas and dust to condense, spin and heat up which forms a proto-star.
Nebula: Accretion disc
There are no nuclear reactions inside the proto-star, it is not a star yet!
Proto-stars
If there is not enough mass to create a protostar, a Brown Dwarf forms.Some astronomers consider Jupiter a Brown Dwarf…
Brown Dwarfs
Eventually the gas shrinks enough that its temperature and density become high enough, that a nuclear fusion reaction starts in its core! -- It becomes a giant Hydrogen Bomb!
A star is born…
At 10 Million K, Hydrogen begins nuclear fusion to form helium and the star begins to shine. It will now be visible on an H-R Diagram.
A star is born…
The star shines as nuclear reactions inside produce light and heat.
Main Sequence Star
How long and how hot the star burns is determined by the star’s mass but…Eventually, stars begin to run out of their fuel hydrogen.The problem is that pressure begins to decrease but gravity stays the same causing contraction, which raises pressure which increases temperature.
How it works:
Hydrogen shell begins to burn rapidly (red layer in the diagram) and this causes the non-burning helium ‘ash’ (yellow layer) to expand. The core shrinks and heats up, the outer layers expand and cool. This is a red giant.
How it works…
Star of less mass expands and glows red as it cools.
Red Giant
In the core, helium begins fusing to make carbon. Temperatures are not high enough to make heavier elements. Helium flash: burning of helium becomes explosive and the outer layers of red giant are ejected in an envelope called a planetary nebula.
Planetary Nebula
Outer layers of gas puff off.
Hot core will be exposed as white dwarf.
Planetary Nebula
Ring Nebula
Dumbbell Nebula
Hourglass Nebula
Ant Nebula
As the envelope recedes, the core becomes visible.
White dwarf
Small, dim and hot.No nuclear reactionsDying star that is slowly cooling off
White Dwarf
A nova is a white dwarf star that suddenly increases enormously in brightness, then slowly fades back to its original luminosity. Novea are the result of explosions on the surface of the star caused by matter falling onto their surfaces from the atmosphere of a larger binary companion.
Nova
Type Ia Supernova
Star cools and reddens.White dwarf cooling
Eventually the white dwarf cools off completely and becomes a cold dense ball called a black dwarf because it does not radiate any energy.
Black Dwarf
Star stops glowing.Black Dwarf
Flow chart: Nebula to white dwarf
Remember, low mass and massive stars for the same way up until the red giant phase.
To be considered massive, a star must be about 8 times larger than our sun.
Now lets talk about massive stars!
Chandrasekhar limit
Massive stars are hot enough to continue to fuse elements until the core becomes iron. Nuclear reactions in stars can’t make heavier elements than iron.
Massive stars
Massive stars
Star of greater mass expands, cools, and turns red.
Supergiant
Core releases an explosive shock wave expelling the outer layers of the star in a tremendous explosion called a type II supernova.
Type II supernova
Supergiant explodes, blasting away outer layers.
Supernova
Intense pressure in the core causes electrons to fuse with protons creating neutrons.
After a supernova: option 1 = Neutron Star
Core collapses and becomes very dense.
Neutron Star
Neutron stars are the densest visible object known.A teaspoon of our sun = 2.1 gramsA teaspoon of a neutron star = 9.75x1014 grams
Sometimes Neutron stars pulse due to electrons accelerating near the magnetic poles and are called pulsars.
Neutron stars
The gravitational pull is so great that nothing can escape it, not even light!
After a supernova: option 2 = black hole
Singularity is the center of the black hole and a point of infinite density. The current laws of physics break down because the circumstances are so extreme.
Blackholes
This is the radius at which the escape velocity equals the speed of light.
The event horizon is the surface of the black hole and the ‘point of no return’.
Schwarzschild radius and event horizon
Core collapses completely and vanishes
Black hole
Flow chart: can you label the parts?
