Cosmology Flashcards
What is the astronomical unit
1.5 * 10^11
What is one arcsecond
1/3600 degrees
Define a parsec
The distance at which 1 Astronomical Unit subtends an angle of 1 arc second
What is stellar parallax
The technique used to determine the distance to stars that are relatively close to the Earth, at distances less than 100 pc.
What is the doppler effect
The perceived change in wavelength of a wave source observed due to relative motion between observer and wave source.
Doppler shifts in starlight
If the galaxy is moving towards us, called blue shift, smaller wavelength than normal. If galaxy moves away, called red shift, greater wavelength than normal.
What is hubbles law
the recessional speed V of a galaxy is directly proportional to its distance d from the Earth.
What is hubbles constant
67.8 kilometeres per second per mega parsec, or 2.2 x 10^-18
What does hubbles law show
Galaxies’ redshifted light shows expanding Universe; space itself expands, causing all points to move away from each other, with more distant galaxies moving faster.
What is the cosmological principle
The Universe is homogeneous and isotropic, and the laws of physics are universal.
What is the big bang theory
All matter in the universe was once contained in a single point at the beginning of space and time.
What is background microwave radiation
Young hot Universe: High-energy gamma photons filled space. Expansion stretched their wavelength to microwaves. Dense, hot start cooled to 2.7 K. Universe acts as a black-body radiator, emitting peak wavelength around 1mm in microwave spectrum.
