Browse by Grade & Topic: Stars and Galaxies

A collection of stars visible from Earth can be arranged and classified based on their color, temperature, luminosity, radius, and mass. This can be done using one or two-dimensional...

Analyze the spectra of a variety of stars. Determine the elements that are represented in each spectrum, and use this information to infer the temperature and classification of the star....

Follow in the footsteps of Edwin Hubble to discover evidence supporting the Big Bang Theory. First, observe Cepheid variable stars in different galaxies to determine their distances. Then,...

FREE with no time limit!

Explore examples of nuclear fusion and fission reactions. Follow the steps of the proton-proton chain, CNO cycle, and fission of uranium-235. Write balanced nuclear equations for each step,...