Question

b) Scientists using the Hubble Space Telescope have observed Cepheids in the galaxy M100. Here are the data for 3 Cepheids in M100:Cepheid 1: luminosity = 3.5 x 1030watts, apparent brightness 9.6 x 10-19watt/m2Cepheid 2: luminosity = 1.1 x 1030watts, apparent brightness 3.9 x 10-19watt/m2Cepheid 3: luminosity = 2.2 x 1030watts, apparent brightness 8.8 x 10-19watt/m2Compute the distance (in lightyears) to M100 with data from each of the three Cepheids.

(c) Do all three distance computations agree?

(d) Based on your results, estimate the uncertainty in the distance you have found. (Uncertainties or errors in observational data are important to understand that accuracy and reliability of measurements!)

(e) Why are white-dwarf Supernova useful for finding the distance to very remote galaxies? Can they be used to find the distance to any galaxy you might choose? Answer in a few sentences.

Answer 1

(c) As you can see all the distances are not the same.

(d) To calculate the uncertainty in distance we need to know the uncertainty in luminosity and apparent brightness.

(e) White-dwarf Supernova is useful for finding the distance to very remote galaxies because White dwarf supernova is much more luminous than Cepheid and can be seen from a large distance away.