Exam 5: Light

The Kelvin temperature scale is used in astronomy because:

You observe a red star and a blue star and are able to determine that they are the same size. Which star is hotter, and which star is more luminous?

At what wavelength does your body radiate the most given that your temperature is approximately that of the Earth, which is 300 K?

If you find that the H-alpha line in a star's spectrum occurs at a wavelength of 656.45 nm, what is the star's radial velocity? Note that the rest wavelength of this line is 656.30 nm.

How are atoms excited and why do they decay?

An asteroid with an albedo of 0.1 and a comet with an albedo of 0.6 are orbiting at roughly the same distance from the Sun. How do their temperatures compare?

Astronomers have now found a large number of exoplanets, which are planets that orbit around stars other than the Sun. Imagine astronomers found a planet identical to the Earth orbiting a star that had the same radius as the Sun, but with a temperature that is twice the temperature of the Sun. How far would this new planet need to be away from its star to have the same average temperature as the Earth?