This page provides a basic introduction to the interstellar medium (ISM) and the physics needed to understand the main components of the ISM and how astronomers study them. It is designed to be a companion webpage for the WorldWide Telescope tour “The Multiphase ISM.” While the tour is aimed at the general public, this website is also intended to provide the interested viewer with a more technically-oriented overview.

ISM Background

Additional background information about topics mentioned in the tour, aimed at the non-specialist. These pages provide a broad overview to the ISM and an introduction to relevant basic physical concepts.

Introduction: What is the ISM?
How dense is the ISM?
What is dust?
Understanding Light: The Electromagnetic Spectrum
Blackbody Radiation
Understanding Spectral Lines
Nuclear Fusion: Why do stars shine?
Supernovae: The Deaths of Massive Stars

Physics of the ISM

A series of pages that provide more detailed information about the stops on the tour and some of the physics behind the phenomena viewed in the tour. These pages are for readers desiring more in-depth information.

Energy sources in the ISM
The Orion Star-Forming Region
Simplified HII Regions: Stromgren Spheres
Jeans Collapse
Shocks in the ISM
The Zeta-Ophiuchus HII Region


These pages link to the official websites of each telescope or survey project that contributed images to the WorldWide Telescope tour and to this website. Many of them include galleries of images and additional information about the ISM and many other topics.

Digitized Sky Survey
Spitzer Space Telescope
Hubble Space Telescope
Chandra X-Ray Observatory
SFD Dust Map (compiled from COBE/DIRBE and IRAS/ISSA)
WHAM (Wisconsin H-Alpha Mapper) — all-sky H-alpha survey

Additional Information

For more information about several particularly interesting objects in the ISM, see the related WorldWide Telescope tour “Landmarks of the ISM” and companion webpage by Meredith MacGregor.

For additional information about WorldWide Telescope, please visit http://www.worldwidetelescope.org.

This page was created in spring 2013 as part of a final project for the class Astronomy 201b: Interstellar Medium and Star Formation, taught by Alyssa Goodman. The class website includes far more information about the ISM than we can feasibly cover here and can be found at http://ay201b.wordpress.com.


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