Astronomy And Cosmology Flashcards
Luminosity
The total power output of radiation emitted by a star
Radiant flux intensity
The observed amount of intensity, or the radiant power transmitted normally through a surface per unit of area, of radiation measured on Earth
What is the inverse square law of flux
F=L/4pid^2
Define Standard candle
An astronomical object that has a known luminosity due to a charecteristic quality possessed by that class of object
Examples of standard candles
1) Cephid variable star
2) type 1a supernova
How do we measure astronomical distances
Using standard candles, we know the luminosity we should measure the radiant flux intensity and calculate the distance using the Inverse square law of flux
Wien’s displacement law
The black body radiation curve for different temperature peaks at a wavelength which is inversely proportional to the temperature
What is wein’s law equation
Wavelength max x frequency = 2.9×10^-3
What does a stars luminosity depen on
1) it’s radius
2) it’s surface temperature
Stefan boltzmann law
The total energy emitted by a black body per unit area per second is proportional to the 4th power of the absolute temperature of the body
Stefan boltzmann equation
4pir^2sigmaT^4
What is the difference in emission spectra in galaxy
1) increase in wavelength
2) shifted towards the red end of the spectrum
Doppler effect
The apparent change in wavelength or frequency of the radiation from a source due to its relative motion away from or toward the observer
If the object is moving away from the earth is it redshift or blueshift
Redshift
Redshift
The fractional increase in wavelength due to the source and observer receding from each other
