Orbiting Astronomical Observatory-2

United States satellite

Also known as: OAO-2

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 20, 2026

Quick Summary

The Orbiting Astronomical Observatory-2 (OAO-2) was a U.S. satellite launched on December 7, 1968. It weighed over 4,200 pounds, making it the heaviest satellite orbited at that time. OAO-2 carried two large telescopes and other scientific instruments. Its primary mission was to observe stars that emit mostly ultraviolet light, which cannot be seen from Earth's surface because the atmosphere absorbs this radiation. This allowed astronomers to detect and study young stars that were previously undetectable. OAO-2 operated successfully until January 1973.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

Orbiting Astronomical Observatory
OAO-2, launched Dec. 7, 1968, carried two large telescopes and a complement of spectrometers and other auxiliary devices. It weighed more than 4,200 pounds (1,900 kg), the heaviest satellite orbited up to that time. OAO-2 was able to photograph young stars that emit mostly ultraviolet…
Read More
OAO-2, launched Dec. 7, 1968, carried two large telescopes and a complement of spectrometers and other auxiliary devices. It weighed more than 4,200 pounds (1,900 kg), the heaviest satellite orbited up to that time. OAO-2 was able to photograph young stars that emit mostly ultraviolet…
Read More