[Astronomical Distances] [Basics of Light] [Tools for Light Analysis] [Measuring Light] [Electromagnetic Spectrum] [Fun with Units] [Atmospheric Transmission] [Space Links]
Ukrainian translation of this web site by Healthpoise.

French translation of this web site by Natalie Harmann (harmann.natalie@gmail.com).


What are Those Squiggly Lines?

Using Light to Learn About the Universe


The above graph shows the brightness (or intensity) of far-ultraviolet light (vertical axis) as a function of wavelength (horizontal axis) for the central star of a planetary nebula known as NGC 1535. Believe it or not, this "squiggly line" is what astronomers call a spectrum! This spectrum tells us that the star is very hot, and yet is surrounded by cooler atomic and molecular hydrogen gas, which causes many of the "squiggles" in the graph. The big squiggle marked "O VI" arises from a huge stellar wind that emanates from the star. That's alot of information to get from a squiggly line! This spectrum was obtained with the Hopkins Ultraviolet Telescope during the Astro-1 Space Shuttle mission in 1990.


Welcome to the Squiggly Lines home page! The purpose of this educational Web site is to make the concepts of light and astronomical spectroscopy understandable at a middle school to high school level. We also discuss a wide range of issues related to spectroscopy, such as the basics of light, the electromagnetic spectrum, atmospheric transmission, and the devices that are used to make measurements of astronomical spectra. Links are provided to a wide range of other sites that contain related information.

The headlines below will connect you to information about each topic listed. Each page is free-standing, but a better understanding can be had by proceeding roughly in the order the topics are presented. Links are provided at the bottom of each page to either go on to the next topic, or return to this page.

The creation of these pages has been supported by a seed grant from the Maryland Space Grant Consortium at Johns Hopkins University. I hope you find these pages helpful, interesting, and educational. Enjoy!

Bill Blair (wpb@pha.jhu.edu).


Astronomical Distances in Perspective

Distances are so large in the astronomy that we have to use the light sent to us from distant objects to learn about them. This page describes astronomical distances in a way that is more understandable than just "numbers."

The Basics of Light

Click here to find out about what light is and does, including sub-sections on Light as Energy, How Light Acts Like Particles and Waves, and How Light Interacts with Matter.

Imaging, Photometry, and Spectroscopy--the Tools of Astronomers

This page discusses some of the primary ways astronomers use light to learn about the Universe around us.

How to Measure a Spectrum

This page will tell you a little about how astronomers use special devices to break light up into a spectrum and measure it. You will also get an inside look at the world of modern astronomy, with electronic detectors and large telescopes.

The Electromagnetic Spectrum

This page describes how optical light is just part of a much broader range of light radiation that includes everything from X-rays to radio waves. All kinds of light can be (and is!) used in astronomy, and different kinds of light open up whole new windows on the Universe!

Fun with Units

The full range of light is so large that astronomers and physicists working in different spectral regions have developed their own special measuring units for dealing with it. But while the units of measurement may be different from one spectral region to the next, they are all measuring the same thing--light! Use this page to learn more about the terminology and units used in various spectral regions.

Atmospheric Transmission--What doesn't get through CAN hurt you!

Many kinds of light are blocked by earth's atmosphere, which is good! But this means we need to get telescopes in space to observe in most of the EM spectrum. Look here to find out what gets through directly and what doesn't.

Spectroscopy in Space

It is only over the last 40 years that we have had the ability to lift telescopes (and spectrographs!) above the atmosphere, which has allowed us to learn many new things about the Universe. Here we highlight a few of the many space missions that have had (or will have) spectroscopy as a primary tool, and (where possible) provide links to other sites that describe these missions in more detail.


[Astronomical Distances] [Basics of Light] [Tools for Light Analysis] [Measuring Light] [Electromagnetic Spectrum] [Fun with Units] [Atmospheric Transmission] [Space Links]

Comments? Click here to send E-MAIL to Dr. Bill Blair

Last updated: March 2004.