Astrophysics Flashcards
Universe
Collection of billions of galaxies
Galaxy
Collection of billions of stars
Fusion
When two small nuclei join together to make one large nucleus
What is fusion the energy source for
Stars
Why does it need to be hot for fusion
The nuclei move very quickly because there is lots of KE, and it can overcome the electrostatic repulsive force
Why does fusion need high pressure
It forces the nuclei closer together which increases the probability of collision
Evolution of low mass stars (like the sun)
Nebula, protostar, main sequence, red giant, white dwarf, red dwarf
Evolution of high mass starts
Nebula, protostar, main sequence, red supergiant, supernova, EITHER neutron star, OR black hole
Nebula formation
Gravitational force causes cloud of dust and gas to attract together
Protostar formation
When there is enough mass in the nebula
Main sequence formation
The gravitational forces are balanced by the radiation pressure, so the star is stable (there is fusion)
Red giant formation
They are very hot in the centre so the star swells because the energy and radiation pressure increases, surface temp gets cooler.
White Dwarf formation
The star collapses from the gravitational forces, surface heats up (no fusion because no energy)
Red dwarf formation
Cools down and turns red (no fusion because no energy)
Supernova
Occurs when fusion stops abruptly, huge explosion radiating energy out into the universe
Neutron star
All neutrons, low mass, no fusion
Black hole
A rip in the universe that nothing can escape from, no fusion
Why would a supernova become a black hole
Higher mass
Why would a supernova become a neutron star
Lower mass
What does a low absolute magnitude of a star mean
A brighter star
Apparent magnitude
A measurement of the brightness of a star as we measure it on earth
Absolute magnitude
A measurement of the brightness of a star if all stars are the same distance away
Why is absolute magnitude useful
Allows us to compare stars
Speed of light
3 x 10^8 m/s
y-axis of HR diagram
Absolute magnitude
x-axis of HR diagram
Surface temperature
Line spectra
Where each element has a particular light that it emits. The different colours are based on the frequency
Doppler effect
moving towards: wavelength decreases and frequency increases
moving away: wavelength increases and frequency decreases
Red shift
When an object emitting light moves away from us, the wavelength increases and appears more red
CMBR
Microwave radiation that is found to exist everywhere in the universe, in all directions
CMBR evidence
As the universe expanded, the wavelength of the radiation also expanded. There had to have been a huge release of energy to produce the radiation
Red shift of galaxies evidence
The galaxies furthest away from us have the greatest red shift, so they are travelling the fastest.
