Chapter 20 - Cosmology

Cards (12)

An astronomical unit is the average distance between the earth and the sun
A light year is the distance travelled by light in a vacuum in one year
A parsec is the distance at which a radius of one AU subtends an angle of one arc second
Dark energy is a hypothetical form of energy that fills all of space and would explain the acceleration of the universe
Dark matter is a hypothetical form of matter spread through the universe that neither emits nor absorbs light and could explain the differences between the predicted and observed velocities of stars in galaxies
To find the degrees of an angle in arcseconds, divide the number by 3600
Stellar parallax is a technique that can be used to determine the distance of stars relatively close to earth (less than 100pc )
Stellar parallax is the apparent shift in the position of a relatively close star against the backdrop of the much more distant stars as the earth orbits the sun
to calculate distance of stars using an angle in arcseconds ; $d\ \left(pc\right)\ =$ $\frac{1}{p\ \left(\operatorname{arcsec}\right)}$
The Doppler effect is the change in frequency and wavelengths of waves received from an object moving relative to an observer compared with what would be observed without motion
For an object moving towards an observer, the waves have been compressed and so have a shorter wavelength and a higher frequency
For an object moving away from an observer, the waves have been stretched and so have a longer wavelength and a higher frequency