- HST (Hubble Space Telescope) records images
with 0.1” resolution. Each stellar position can be centroided to about 10%
accuracy. At what distance can HST measure a distance to 10% accuracy? How
well can it measure at the ecliptic pole? Voyager carries a telescope with
2” resolution and 10% centroiding. At what distance from the Sun could it
- You measure a signal of 200c/s in B, and
1000c/s in V. What is B-V? What is
the spectral type if there is no reddening? What is the spectral type if Av is 2 magnitudes?
- You make an HR diagram for a cluster and find
the main sequence turnoff is near spectral type A1. About how old is the cluster?
- You take multiple images of a galaxy and
detect a star of magnitude 27 varying with a period of 50 days. How far
away is the galaxy?
- You detect the Lyman a
emission line (1216Å) from a distant galaxy at 1425Å. How fast is the
galaxy receding? Calculate values
for z and cz. What is its
- If there is no acceleration or deceleration,
then the inverse of the Hubble constant is the age of the universe. If the
Hubble constant were 55km/s/Mpc then how old would the universe be? What about 75km/s/Mpc, and
110km/s/Mpc? Hubble first
estimated 500km/s/Mpc. What is the
problem with this number?
- The Milky Way is traveling about 400km/s
relative the Hubble flow (the term for the average of the universe). How far way must you calibrate the H0
to make this offset insignificant?