Imagine the Universe!
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Introduction to High-Energy Astrophysics

The night sky has always served as a source of wonder and mystery to people. However, it has only been in the past few decades that we have truly begun to 'see' the universe in all its glory. This is because we have only recently been able to look at the universe over the entire electromagnetic spectrum.


* What is the electromagnetic spectrum anyway?

Instruments to probe the wide range of the electromagnetic (EM) spectrum have been available to us only in the 20th century, and the rocket age was required to get instruments sensitive to the infrared, ultraviolet, X-rays, and gamma-ray wavelengths above the Earth. This "view from space" is critical since radiation in these ranges cannot penetrate the Earth's atmosphere. Nevertheless, outside the range visible to us with our eyes, the universe produces a vast array of radiation with wavelengths either too short or too long for our eyes to see. In fact, many objects in the heavens can be detected only in one of the other regions of the EM spectrum. And most all objects can only be fully understood by combining observations of their behavior and appearance in all the different regions. Putting these pieces of information together allows scientists to begin a full understanding of the celestial inhabitants.

* Show me an object seen in different parts of the electromagnetic spectrum
* A Radio Wave is not a Gamma-ray, a Microwave is not an X-ray... or is it?
* Why do we have to go to space to see all of the electromagnetic spectrum?

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

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