Guide to Expeditions

Our Expeditions are designed for intermediate to advanced students.  Many of these activities lead to open-ended extensions, designed to encourage students to practice science by formulating their own questions and by accessing data to pursue new and novel hypotheses.  In general, these projects require extended periods of time to complete as well as the use of spreadsheet programs that enable the plotting of data (e.g., Excel or Google Sheets). Prior experience working with such software will be helpful.

We invite you to share your needs, interests, and challenges with us. And if your students find that they have learned something extraordinary while on their Expedition, let us know that as well! We may try to replicate it for future travels (and travelers) on our site.

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Expeditions to the Milky Way

Star Clusters

This activity guides students through producing and analyzing Hertzsprung-Russell diagrams of star clusters. The first section explores the creation of color-magnitude diagrams, starting with choosing a cluster, and then progresses through the steps required for data extraction and analysis.

Spectral Types

The classification of stars by their spectral features is fundamental to our understanding of stellar populations and galaxies. This activity introduces students to the variety of spectral types of stars in our Milky Way galaxy, and dives into the atomic physics underlying the absorption features that lead to these classifications. For more information, see our teacher notes.

Expeditions to Galaxies

Galaxy Color

Learn why galaxies come in different colors, and what those colors can tell us about what galaxies are made of.

Sky Surveys

The Sloan Digital Sky Survey is not the first effort to map the night sky. Ancient astronomers made maps of the night sky relying on nothing more than their own eyes, meticulously writing down their results.

Technology has improved considerably in the 20th century. Fifty years ago, the Palomar Observatory All Sky Survey (POSS) was completed. Today, in addition to the SDSS, many other all-sky maps are being made. Most of these maps look at the sky with different parts of the electromagnetic spectrum than the SDSS. Different wavelengths of light convey different information about celestial objects, and so give us a more complete understanding of them.

Galaxy Properties

The Sloan Digital Sky Survey has observed hundreds of millions of galaxies. In this activity, students will learn about those galaxies: how to classify them, what their important characteristics are, and how astronomers think they evolve.

Expeditions to the Universe

The Expanding Universe

This Expedition retraces the historic research that established the relationship between redshift and distance in galaxies. Students use an SQL query to retrieve the data needed to construct a color-magnitude diagram from the Abell cluster of galaxies, revealing the 1936 redshift-magnitude relationship from Hubble and Humason’s ground-breaking paper.

The Universe: Your Cosmic Address

This Expedition introduces the idea that the Universe is expanding, and addresses some common student misconceptions about what that means.

The Hubble Diagram

The idea that we live in an expanding universe is one of the most unexpected and important discoveries of 20th century physical science. For tens of thousands of years, everyone, including astronomers, had assumed that the universe was a stable, unchanging stage on which astronomical events played themselves out. But in the 1910s and 1920s, several physicists and astronomers made several discoveries that defied easy explanation. These discoveries started to come together in the late 1920s, and finally in 1929, an astronomer named Edwin Hubble published a paper that helped to explain these results. In this project, students will retrace Hubble’s steps, seeing the same bizarre phenomena that he saw, and discover for themselves that the universe is expanding. 


One of the principal goals of the SDSS is to find the most distant objects ever observed. The light from these distant objects has taken billions of years to reach us. So when we look at them, we are seeing them as they appeared billions of years ago.

But at such enormous distances, the only objects we can see at all are the very brightest objects. This activity explores the brightest and most distant objects in the universe: quasars. Students will learn what they are, what provides their enormous power, and what they can tell us about the early universe.