NASA's Great Observatories

Each portion of the electromagnetic spectrum (X-rays, gamma rays, ultraviolet, visible, infrared and radio) brings us unique information about the Universe and the objects within it. X-rays and gamma rays bring us information about high energy phenomena such as black holes, supernova remnants, hot gas, and neutron stars. Ultraviolet light reveals hot stars and quasars, while visible light shows us warmer stars, planets, nebulae and galaxies. In the infrared we see cool stars, regions of starbirth, cool dusty regions of space, and the core of our galaxy. Radiation in the radio region shows us cold molecular clouds and the radiation left over from the Big Bang. If we want to better understand the Universe, we need to study it in all of its light - across the electromagnetic spectrum. To achieve this goal, NASA created the Great Observatories Program - a series of four space observatories designed to gather light across the spectrum.

The first Great Observatory to be launched was the famous Hubble Space Telescope (HST). Launched in 1990, Hubble is a long term space-based observatory designed to gather visible, ultraviolet, and near-infrared light. It is regularly upgraded with improved optics and instruments.
The second Great Observatory, launched in 1991, was the Compton Gamma-Ray Observatory (CGRO). Designed to observe high energy gamma rays, this observatory continues to collect information on some of the most violent processes in the Universe.
Third in the series is the Chandra X-Ray Observatory(CXO). Launched in 1999, this observatory is used to study X-rays from objects such as black holes, quasars, and regions containing high-temperature gases.
The Spitzer Space Telescope is the fourth and final mission in NASA's Great Observatories Program. Scheduled for launch in 2003, Spitzer will study the infrared radiation from space. Spitzer is also part of NASA's Astronomical Search for Origins Program, designed to provide information which will help us understand our cosmic roots, and how galaxies, stars and planets develop and form.

To learn more about the value of observing the Universe across the electromagnetic spectrum, visit our web site on Multiwavelength Astronomy.