Project Overview

You will be given a list of galaxies that you will include in your description of Hubble's law. For each galaxy,you will need to find the luminosity distance and the radial velocity. You can find this information on the NASA/IPAC Extragalactic Database (NED). On NED, you will sarch by object name (first column, first row). The page of results for each object will come in an index. Click on the link for "Basic Data" to find the radial velocity:



The radial velocity shown in the example above is 3901 km/s. The "+/- 10 km/s" represents the error in the measurement, which we won't need to know for this project. Going back to the index, click on the link for "Quantities Derived from Redshift" to find the luminosity distance:



The luminosity distance in the example above is 51.1 Mpc (megaparsecs, with 1 Mpc = 1 million pc). These are the units you want to use: km/s for radial velocity, and Mpc for distance.

What you will be doing with this data is plotting it on a radial velocity vs. distance graph. (For instructions on how to plot using Excel, click on this link.) With the data plotted, you can find the equation for the line. The data should represent a straight line, which means that the equation will be y = mx, where y is the vertical axis (the radial velocity), x is the horizontal axis (the distance), and m is the slope of the line. If we call the slope H, then we find the equation v = Hd, which is known as Hubble's law. Your job will be to use the data plot to estimate the Hubble constant, H, which is the slope of the data plot.

What you will turn in will be the excel file that indicates the Hubble constant.

Student Data Sets