Stars And Cosmology Flashcards
What is a planet?
An object orbiting a star with:
No fusion reactions
Cleared orbit of other objects
It has a mass large enough that gravity gives it a round shape.
What are planetary satellites?
A body in orbit around a planet.
Moons
Man made satellites
What are comets?
Irregular bodies made up of ice, dust and small pieces of rock. Comets orbit the sun
What is a solar system?
Contains a sun with bodies that orbit around it
What is a galaxy?
Collection of stars and interstellar dust and gas.
What is a universe?
All of electromagnetic radiation, matter and energy. All of space time and everything within it.
What pushes against the gravitational forces in a star?
Radiation pressure from the photons emitted in nuclear fusion.
Gas pressure from the nuclei.
How does a protostar form?
Charged particles in dust and gas attract each other, gaining mass. Denser regions gain more mass, accelerating the gravitational collapse and therefore become more dense. They also get hotter as gravitational energy is transfere to thermal energy.
What does a protostar need to become a star?
Nuclear fusion
Why is it rare that protostars become stars?
Extremely high pressures and temperatures are required to overcome the repulsion of the nuclei of two hydrogen atoms.
What happens to the Sun after hydrogen runs out
Sun become a Red Giant
Nuclear fusion stops.
Gravitational Force > Radiation + Gas Pressure.
Core collapses.
Fusion continues in the shell around the core.
outer layers expand and cool,
outer layers are released.
This forms a planetary nebula
The-core is left as a white dwarf.
What are the characteristics of a white dwarf?
Very dense
Mass similar to the sun’s
Volume of the earth
No fusion takes place in a white dwarf
Emits energy due to leaked photons produced earlier
Surface temperature of 30,000K
What is the Chandrasekhar limit?
Electron degeneracy pressure only works if the mass of the star is less than 1.44M
How does a red supergiant form?
When the Hydrogen runs out, helium fuses together to prevent the gravitational collapse. The energy released overcomes the electrostatic repulsion so it fuses to form heavier elements. The core expands and the temperature and pressure are high enough to fuse to form heavy elements until it reaches iron. Nuclear fusion of iron doesnt release energy.
What occurs in a supernova?
Iron cannot fuse to release energy. The makes the red super giant very unstable and layers are bounced off the core in a catastrophic implosion.
