Astronomy 100 - Problem Set 5

Due: Tuesday 1 April 2008
Name:

Fill in the box with the correct answer (answers should be just a few words or a number).

  1. What temperature scale (Fahrenheit, Celsius, Kelvin) do most astronomers use in their calculations?

  2. The Stefan-Boltzmann Law says that the total energy radiated in 1 second from 1 square meter of an object is given by the equation E= T4 and the energy is expressed in Joules If the surface of the sun's photosphere is about 6000 K and a sunspot is about 4000 K what fraction less energy is radiated in 1 second from 1 square meter of a sunspot than from 1 square meter of the sun's photosphere?

  3. Consider two stars of the same radius. Star A appears red. Star B appears blue. If both stars appear to have the same brightness when seen in the night sky, which one is closer to us? (Think about the following questions: Which star is hotter? If they were placed side by side, which one would be brighter?)

  4. How much does the luminosity of a spherical blackbody increase if you triple its radius?

  5. Which is coldest: 100 degrees Farenheit, 100 degrees Celsius, or 100 degrees Kelvin?

  6. If you made observations of stellar parallax from Venus, which orbits closer to the Sun than the Earth, would the parallax motion of a given star appear larger or smaller than the motion observed from the Earth?

  7. If you were on one of the satellites of Jupiter, 5.2 times as far from the Sun as the Earth, how much fainter would the Sun appear than it does from the Earth?

  8. You observe a binary star system made of star A and star B with an average separation of 6 au and a period of 3 years. Suppose star A is 2 au from the center of mass and star B is 4 au away from the center of mass. What is the mass of star A in solar masses?

  9. A 2 liter bottle of Coke weighs about 2 kilograms. If that bottle were combined with an equal amount of anti-Coke, how many Joules of energy would be released (note that you get units Joules if you calculate the energy using units of kilograms and meters)?

  10. The United States consumes 3x1012 Joules of energy every second. For how long would the energy generated in Question 9 above sustain this country's energy needs?