Steps to the Hubble ConstantWhy care so much about finding distances in astronomy? If you know the distance to a star, you can determine its luminosity and mass. You can then discover a correlation between luminosity, mass, and temperature for main sequence stars that our physical theories must account for. Finding distances to stellar explosions like planetary nebulae and supernovae enables you to find the power needed to make the gaseous shells visible and how much was needed to eject them at the measured speeds. Stellar distances and distances to other gaseous nebulae are necessary for determining the mass distribution of our galaxy. Astronomers have then been able to discover that most of the mass in our Galaxy is not producing light of any kind and is in a dark halo around the visible parts of the Galaxy. Finding distances to other galaxies enables you to find their mass, luminosity, and star formation history among other things. You are better able to hone in on what is going on in some very
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