Answer
See answers.
Work Step by Step
These techniques are discussed in sections 33-3 and 33-5.
Measuring the distance to relatively close stars:
i. Up to 100 ly away from Earth, parallax is used to measure distance. We observe the amount that a star moves (relative to the fixed background of very distant stars) as the Earth orbits the sun. Example 33-6, page 958, illustrate show to use parallax.
ii. We observe the apparent brightness of the brightest stars in various galaxies, and assume that the intrinsic luminosities of these stars are equal. Light intensity follows an inverse square law, so we can estimate distances to various galaxies.
iii. Similar to technique ii. Determine the surface temperature of a star using its emission spectrum (assuming it is a blackbody) and Wien’s law. Use the H–R diagram to estimate its intrinsic luminosity. Finally, use its apparent brightness and equation 33-1 to find the distance.
iv. Similar to techniques ii and iii. Variable stars (e.g., Cepheid variables) have a period-luminosity relationship that is well-known and calibrated. Use its apparent brightness and equation 33-1 to find the distance.
Measuring the distance to very distant stars:
v. Type Ia supernovae are thought to have roughly the same luminosity. Use the apparent brightness and equation 33-1 to find the distance.
vi. Measure the redshift in the spectra of elements and compounds. The farther the galaxy, the faster it is moving away from us and the greater the redshift.
