Stars Flashcards
Define planets
- has mass large enough for gravity to give it a round shape
- has no fusion reactions
- has cleared it orbit of other objects like asteroids
What are planetary satellites?
- a body in orbit around a planet
What’s an example of a planetary satellite?
Moon or Satellite
Define a comet
Small irregular bodies made of ice, dust and rock.
They orbit the sun in elliptical orbits
How do the majority of comets orbit?
Elliptical orbits
Define a solar system
A system of plants that orbit a sun
Define a galaxy
A collection of stars and interstellar dust.
What does a Hertzsprung- Russell diagram show?
The relationship between the luminosity of a star and its temperature
What star has a very high temperature but low luminosity?
White dwarf
Name 3 characteristics of white dwarfs
- Very dense
- no fusion reaction occurs
- surface temperature up to 30000K
Define the protostar stage
A sphere of hot gas that allows hydrogen gas to undergo fusion and produce helium nuclei
Define electron degeneracy pressure
The pressure when electrons are squeezed together as the core of a star collapses. Which prevents further gravitational collapse
Define Chandrasekhar Limit
The maximum mass of stars where electron degeneracy pressure applies.
(1.44M©️)
What are the characteristics of a black hole
~very dense
~has mass greater than 3M
~has a gravitational field so strong light cannot escape
How does a low mass star become a red giant?
A star runs low on Hydrogen and less energy is released by fusion so the core cools down and collapses.
Fusion occurs in the outer shell
How is a planetary nebula formed?
When the outer shells of a red giant cools and drifts away
What’s the mass of a massive star
> 10M
State Wien’s Law
The maximum wavelength of a black body is inversely proportional to temperature
Lambda x Temperature = constant
State Stefan’s Law
The total power radiated per unit surface area of a black body is directly proportional to the fourth power of temperature.
L=4πr²σT⁴
What is the path difference of two adjacent waves at first order maxima?
λ
Explain how absorption line spectra works
- Light with a continuous spectrum passes through a cooler gas.
- some photons are absorbed by the gas, making electrons excited
- specific wavelengths of photons are absorbed, creating dark lines in the continuous spectra
Explain why a red giant is brightest when it is at its coolest
- Red giants have a large surface area
- and radiate large amounts of energy
- so greater intensity of light making it bright
Explain how low mass stars like our Sun is formed
- Gravitational attraction forms clouds of dust which become denser.
- gravitational energy is transferred to thermal energy
- protostar- a sphere of hot gas allows hydrogen to fuse and form helium nuclei.
- a stable equiulibrium is formed where radiation pressure from fusion counteracts compression due to gravity.
Explain how massive stars form red supergiants to supernova to black hole
- A hotter core means Helium nuclei fuse into heavier elements.
- Helium nuclei have enough KE to overcome repulsive forces.
- Massive nuclei fuse together so multiple shells form.
- The red supergiant has an iron core which doesnt fuse.
- The star becomes unstable and implodes forming a supernova
- Gravitational collaspe compresses the core, forming a black hole.
How is a neutron star formed from a supernova?
From the supernova explosion, electrons and protons begin to form neutrons due to gravitational compression forming a dense neutron star.
