Transcript life cycle of stars

LIFE CYCLE OF STARS
VYVY DONG, ABBY HATFIELD, & MACKENZIE OCHILTREE
Nebula
★ Giant cloud of gas and dust
★ Various things other than planets and comets
★ Reserved for gas and dust clouds
★ Various forms:
○ Emission Nebula - clouds of high temperature gas
○ Reflection Nebula - clouds of dust reflecting light from nearby stars
○ Dark Nebula - block light from whatever is behind
○ Planetary Nebula - shells of gas thrown from stars near the end of life
MASS
★ Life cycle determined by mass
○ Larger mass, shorter life cycle
○ Amount of matter in its nebula
★ Nebula
○ Gravity pulls hydrogen gas together in nebula
○ Heats up and transforms to a protostar
★ Protostar - mass of gas that represents an early stage of a star
★ Nuclear Fusion - process where small nuclei are combined to make a larger one.
MAIN SEQUENCE
★ Hertzsprung-Russell Diagram
★ Stars continue to burn energy and glow
★ Majority of their lifespan
★ During this stage:
○ Gravity shrinks, heat grows
○ Hydrogen turns into helium through nuclear fusion
○ Remains this way until it runs out of hydrogen
○ Core is unstable and contracts
RED GIANT
★ Red Giant - star with a low surface temperature
○ Helium fuses into carbon
★ May grow to more than 400x its original size
★ Red Giants are also known as red supergiants
★ Engulfs some close-orbiting planets
★ All stars evolve the same way until this stage
LOW MASS STARS
★ Core runs out of fuel for fusion and collapses
★ Ejects the stars outer layer and drift into space
○ Forms a planetary nebula
★ Contracts under gravity and forms a white dwarf
★ White dwarf - hot core that remains and eventually cools
★ Black dwarf - last stage of low mass stars; theoretical as the universe is still too
young to produce them
HIGH MASS STARS
★ Undergo a massive explosion
○ Sharp brightness, gradual decrease
○ Peak brightness: supernova explosion
★ Supernova Explosion types:
○ Type I - accumulates matter from nearby
neighbor until nuclear reaction occurs
○ Type II - runs out of nuclear fuel and
collapses under its own gravity
■ Density cannot be measured
■ Distort space and suck in neighboring
matter
★ After the explosion:
○ 1.4 - 3 times as massive as our Sun, then it
becomes a neutron star
■ Small, but incredibly dense
■ Rotate in space
○ More than 3 times, it becomes a black hole
■ Gravity pulls so much that even light
cannot get out
Left: Low Mass Stars
Right: High Mass Stars