Chapter 19: Stars Flashcards
planets
Object that:
- orbits the sun
- sufficient mass for self-gravity
- cleared the neighbourhood around its orbit
dwarf planet
planet that has not cleared the neighbourhood around its orbit
planetary satellites
bodies that orbit a planet
asteroid
too small and uneven to be planets
near circular orbit around the Sun
comet
small, irregular sized balls of rocks, dust and ice.
orbit sun in eccentric elliptical orbit
solar system
A planetary system consisting of a star and at least one planet in orbit around it
galaxies
a collection of stars, dust and gas
nebulae
gigantic clouds of dust and gas, birthplace of stars
How are protostars formed?
Gravity draws matter towards dense regions in nebulae
GPE converted into thermal, resulting in a hot, dense sphere of dust and gas
How are main sequence stars formed?
Hydrogen nuclei overcome electrostatic repulsion and fuse to form helium
During fusion, outward pressure and inward gravity are in equilibrium
Describe how a low-mass main sequence star becomes a red giant
Small, cooler core, so MS for longer
Once H low, gravity causes core to collapse and outer layer expands and cools.
Core becomes hotter as GPE converts to thermal, and helium fuses into heavier elements
H fuses in layers around core
Describe the evolution of a red giant to a white dwarf?
When star runs out of fuel, expels outer layers, creating planetary nebula
Core remaining contracts further, now dense white dwarf. White dwarf of around 3000K, and no fusion occurs.
Photons produced earlier leak out, dissipating heat
As core collapse, electron degeneracy pressure prevents collapse, now stable due to Chandrasekhar limit
Describe the evolution of a high-mass main sequence star into a red supergiant
As H depletes, core contracts.
GPE turns to thermal and core much hotter due to higher mass, allowing He fuse to C
Outer layer expand and cool, form red supergiant
Describe the process of the death of a high mass star
When red supergiant fuel used up, fusion stops
Gravity greater than outward pressure and core collapses, becomes rigid
Outer layer falls in and rebound off rigid core, launching shockwave
Remaining core of supernova is neutron star or black hole, depending on mass
Describe the evolution of a red supergiant to a neutron star
if greater than 1.44Mo, gravity forces protons and electrons together to form neutrons, producing small, dense neutron star
