Astronomy & Cosmology Flashcards
State what is meant by the luminosity of a star.
It’s the total power of radiation emitted by the star.
State wien’s displacement law.
The wavelength of maximum intensity is inversely proportional to thermodynamic tempreture.
State what is meant by redshift.
Wavelength is greater than known value due to movement of star away from oberserver
Explain how cosmologists are able to determine that light from a distant star has undergone redshift.
By examining the lines in the spectrum of light from the star, and comparing with known spectrum.
State hubble’s law.
Speed is directly proportional to distance, where speed is the speed of recession of galaxy (from observer) and distance is distance of galaxy away from observer.
Explain how cosmologists use observations of emission spectra from stars in distant galaxies to determine that the universe is expanding.
Cosmologists use observations of redshift, where the wavelengths of spectral lines from stars in distant galaxies are greater than their known values, indicating that these objects are moving away from Earth.
Explain how hubble’s law and the idea of the expandin universe lead to the big bang theory of the origin of the universe.
Hubble’s law dictates that all parts of the universe are moving away from each other, with more distant objects moving away faster. This observation implies that if we trace this motion backward in time, matter must have been closer together in the past.
State what is meant by a standard candle.
An object which has a known luminosity.
