Using Astronomical Scales Flashcards
What is an Astronomical unit
mean distance between earth and sun
What is the size of the observable limited by and why?
Speed of light . It takes time for us to see and universe has finite age so can only see so far
Explain Hertzsprung russel diagram?
- Clusters plotted on luminosity against temp
- More massive stars use fuel quick quicker so spend less time in main sequence
- Assume most massive star in main sequence is about to leave and caluclate time its beeing in main sequence
How can we measure distances in the solar system?
Radar pulses
What is radar?
Pulse of radio waves that hits distant object and is seflected back to eart
What are the assumptions for radar?
Travel at a comstant speed of light
Time taken on the way there is equal to the way back
What is red shift?
When a light source moves away the wavelengths get longer
Shift to red end of spectrum
What is the doppler effect?
When the frequency and wavelength change as waves bunch together in front of object and stretch out behind it
What is doppler shift dependant on?
Velocity
How is an absorbtion spectra produced?
Radiation emitted from star viewed through cloud of cool gas
Atoms in gas absorb certain wavelengths producing dark absorbtion
Each atom is made up of characteristic energy levels so the composition of the atoms in star can be calculated.
The position of absorbtion lines can be compared to the same spectrum of atoms recorded in the lab to shows how much the spectrum has been shifted
Shows how fast it is moving away.
When is relativistic time dialation noticable?
Close to the speed of light
Wordlines show
Paths of Objects moving through space and time
