Astrophysics 2
- Created by: Sagaana
- Created on: 03-02-20 13:07
View mindmap
- Astrophysics 2
- Stars 2
- HR diagram
- The sun has the absolute magnitude of +5 and temperature of the sun is 5700 (G class)
- Red giants have a high luminosity and low temperature so they have a high surface area->gaints
- White dwarfs have a low luminosity but high temperature so they have a low luminosity ->dwarfs
- Stellar Evolution
- nebula
- protostar
- main sequence
- Red giant
- White Dwarf
- low mass stars turn into white dwarfs
- prevented from collapsing by electron degeneracy pressure (electrons that exert enough pressure)
- White Dwarf
- Red super giant
- supernova
- black hole
- escape velocity greater than the speed of light
- gravitational field is strong enough to prevent light from escaping
- Quasars
- They are active galactic nuclei
- supermassive blackholes at the centre of galaxies which are feeding (matter falling into these black holes)
- Bright radio sources
- show a large optical red shift
- produced a continuous spectrum = red shifted blamer line
- show a large optical red shift
- Most distance measurable objects due to their brightness
- schwarzschild radius = the distance at which the escape velocity is the speed of light
- Neutron star
- composed only of neutrons (protons and neutrons fuse together due to gravity)
- has density of nuclear matter
- A star whose absolute magnitude increase enormously and rapidly
- Happen star runs out of fuel and collapses
- Gamma rays produced (similar to the total energy output of a star )
- highly collimated >>>>>DEATH
- black hole
- supernova
- Red giant
- main sequence
- protostar
- nebula
- HR diagram
- Cosmology
- Doppler effect
- redshift = increase in wavelength of a wave due to the relative motion between an object and observer
- only true when v is less than speed of light
- aka "z" can either be red-shift or blue-shift
- velocity is away from observer
- blueshift opposite of redshift
- velocity towards the observer
- can be seen in spectral lines
- redshift = increase in wavelength of a wave due to the relative motion between an object and observer
- Hubbles law
- recessional velocity is directly proportional to its distance away from us
- due to the expansion of the universe /stretching out of space
- goes through origin
- the age of the universe = 1/H(flip the equation)
- typical age of the universe = 14 billion years
- This assumes that H is constant and that the universe is expanding at a constant rate.
- measurement made of type 1a supernovae do not agree with Hubble's law.
- the expansion of the universe is accelerating and this is cause by dark energy.
- measurement made of type 1a supernovae do not agree with Hubble's law.
- recessional velocity is directly proportional to its distance away from us
- Big Bang Theory
- CMBR
- EM radiation coming from all parts of the universe
- the radiation has red shifted into the microwave region as universe expanded
- Produced when the universe cooled after the big bang for combination of electrons and protons to form atoms
- EM radiation coming from all parts of the universe
- There is a lot of hydrogen and helium
- alot of fusion of H and He occured after the big bang
- this stopped as the universe expanded and cooled
- ratio H:HE >>> 3:1
- alot of fusion of H and He occured after the big bang
- CMBR
- Detecting Binary Stars and Exoplanets
- Binary stars
- Most binary stars are so far away that they cant be resolved
- Method 1: Eclipsing binary stars
- the apparent brightness of the system will decrease when the stars eclipse each other
- this effect is greatest when the dimmer star blocks light from the bright star
- the apparent brightness of the system will decrease when the stars eclipse each other
- Method 2:Doppler Shift
- each star will periodically shift because the relative velocities of each star will change during the orbital period
- If there have equal mass the shift of both stars will be the same wavelength.
- exoplanet
- They are difficult to detect due to
- small angle subtended by planet so telescope resolution is not good enough
- The brightness of the planet obscures the brightness of the planet.
- Detection method 1: Direct observation
- difficult to see
- Detection method 2: Transit method
- The brightness of a star is measured over a long time period
- When planet passes in front of a star, some light is absorbed
- Drawback
- planet must directly pass between us and the star
- Transit time is short compared to entire orbit time
- fluctuation in stars brightness can be cause by other means
- other methods must be used to confirm the planets existence
- Detection method 3:Radial Velocity
- the star is monitored over a long period
- The star wobbles backwards and forward periodically
- this the stars velocity relative to the Earths change
- a small can be detected in the stars spectrum
- Drawback
- this requires correct orientation of stars
- other planets can make the star wobble so difficult to analyse
- the wobble must me detectable so the planet must be larger orbiting close to the star.
- They are difficult to detect due to
- Binary stars
- Doppler effect
- Stars 2
Similar Physics resources:
Teacher recommended
Comments
No comments have yet been made