Transcript: Galaxy colors are indicative of their stellar populations, that is the distribution of colors of the stars in the galaxy based on their masses and luminosities. The stellar populations of elliptical galaxies are generally old, and so elliptical galaxies appear red. The bulges of...

Transcript: It sounds simple to measure the size of a galaxy, but it is not because galaxies do not have sharp edges. As you can see in any deep image of a galaxy, the brightness of the stars that the galaxy contains just fades away gradually until it disappears into the darkness of the night...

Transcript: The distances to galaxies are measured by a range of indicators, and the most distant galaxies are only measured using redshift as the distance indicator. Thus we need a model for the expansion of the universe, the Hubble expansion, to estimate the distance to the most distant...