Weekly Online Lesson Online Lesson Archive Grade Level: 8-12 Subject: Astronomy

Compton Returns to Earth

On June 4, 2000, NASA engineers aimed the Compton Gamma Ray Observatory at the Pacific ocean and fired the rockets. It soon entered earth's atmosphere where it burned, broke apart, and plunged harmlessly into the ocean.

When a gyroscope on the spacecraft failed last year, Ed Weiler, NASA's chief scientist, decided to ditch safely it while they still had control. As it is, the craft exceeded its expected mission lifetime by more than four years. It could have stayed in orbit for another 11 years, but if more equipment failed engineers might not be able to control the vehicle and it would make a dangerous random return to Earth.

In nine years of observations, the Compton Observatory has changed the way astronomers view the universe. Compton discovered hundreds of previously unknown sources of gamma rays, including 30 new and exotic objects that are still not completely understood. It detected gamma rays streaming from black holes, from exploding stars and from the sun.

What are gamma rays and how are they changing our view of the universe? You'll learn more about gamma rays in this week's online lesson.

Gamma Ray Bursters

Begin your investigation into gamma rays at the Gamma Ray Bursters page on the Windows to the Universe site. This page gets right to the point of telling you what gamma rays are and what might be creating them. The information is available in Beginner, Intermediate, and Advanced formats; read the one most appropriate to your English reading level.

Imagine the Universe

For more on gamma ray astronomy visit the Basic Gamma Ray Astronomy page, part of NASA's Imagine the Universe Web site. From here there are two topics labeled Level 1 and Level 2. Read the Level 1 information page, beginning with the history of gamma ray research. Hyperlinked terms are those found in the online dictionary; click them if you need to know the definition. Why could gamma-ray astronomy not begin until the development of balloons or spacecraft? What can gamma rays tell us about the cosmos?

If you have Quicktime or an AVI player, download and watch the movie about gamma-rays. And when you reach the end of the page, click on links to the various gamma-ray targets: Gamma-ray Bursts, Black Holes and Neutron Stars, Supernovae, Pulsars, Unidentified Sources, Diffuse Emission, and Active Galaxies - Seyferts and Quasars.

Autopsy of an Explosion

What happens during a gamma-ray burst? Scientists have been studying the answer to that mystery for years. To read what they've come up with so far, read Autopsy of an Explosion from NASA Science News. Far from a traditional news article, this report goes in-depth (from a student perspective) explaining how and why gamma rays act the way they do. What happens when gamma rays pile up? What causes gamma-ray bursts? What is the difference between a beamed and an isotropic explosion?

When your reach the end of the page, don't hesitate to click on related Web links to other gamma-ray stories.

© Copyright 2002
Learners Online, Inc.