- American Association of Variable Star Observers
- American Astronomical Society
- Astronomical Data from the U.S. Naval Observatory
The Astronomical Applications Department of the U.S. Naval Observatory computes, from fundamental astronomical reference data, the position, brightness, and other observable characteristics of celestial bodies, as well as the circumstances of astronomical phenomena."
- Astronomical Society of the Pacific
- The Astronomy Net
This web site is divided into the following sections: Astronomy, Science and Other Discussion Forums, Astronomy Articles, Astronomy Clubs, Amateur Radio Astronomy Net, Calendar of Events, Constellations, and Image Gallery.
"The mission of AstronomyLINKS is to provide an index of the best astronomy and space related web sites found around the world on the Internet."
- Astronomy Online
This site is an "information website dedicated to providing up-to-date links and information in all the major topics of Astronomy. This site is also designed to be a students reference as well as a resource for amateur astronomers." It is divided into the following sections: Observation, Science, Solar System, Stars, Our Galaxy, Cosmology, Astrobiology, Exoplanets, Astrophotography.
- Eric Weisttein's World of Astronomy
This site is a web encyclopedia with over 588 entries that range in length from definitions to full articles.
- Gazetteer of Planetary Nomenclature
"Planetary nomenclature, like terrestrial nomenclature, is used to uniquely identify a feature on the surface of a planet or satellite so that the feature can be easily located, described, and discussed."
This site is devoted to information about NASA's Hubble Space Telescope. It contains news and photographs of "stars, planets, galaxies, nebulae, and strange celestial phenomena" taken by the telescope; as well as an astronomy reference desk.
- International Astronomical Union
- Journey Though the Galaxy
This site "is a "mini-net" of pages that explores our solar system, stars, extra-solar planets, the theories about the past and future of the universe, and human exploration of space."
- Lunar and Planetary Institute
- NASA Images
"NASA Images is a service of Internet Archive, a non-profit library, to offer public access to NASA's images, videos and audio collections."
- Nine Planets: A Multimedia Tour of the Solar System
"This website is an overview of the history, mythology, and current scientific knowledge of the planets, moons and other objects in our solar system." It is intended for general audiences, little technical background is needed. This site consists of approximately 100 pages, one page for each major body in the Solar System.
- The Planetary Society
This Society "is the largest and most influential public space organization group on Earth." It was founded in 1980 by Carl Sagan, Bruce Murray, and Louis Friedman.
- SAO/NASA Astrophysics Data System
"The SAO/NASA Astrophysics Data System (ADS) is a Digital Library portal for researchers in Astronomy and Physics, operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant. The ADS maintains three bibliographic databases containing more than 9.6 million records: Astronomy and Astrophysics, Physics, and arXiv e-prints. The main body of data in the ADS consists of bibliographic records."
- Skyview: the Internet's Virtual Telescope
"SkyView is a Virtual Observatory on the Net generating images of any part of the sky at wavelengths in all regimes from Radio to Gamma-Ray." This site is a service of the Astrophysics Science Division at NASA/ GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory.
- U.S. National Virtual Observatory
"The Virtual Observatory (VO) embodies the concept of large scale electronic integration of astronomy data, tools, and services on a global scale in a manner that provides easy access by individuals around the world. The primary emphasis of the VAO is to provide new scientific research capabilities to the astronomy community."
- Views of the Solar System
This website "presents a vivid multimedia adventure unfolding the splendor of the Sun, planets, moons, comets, asteroids, and more. Discover the latest scientific information, or study the history of space exploration, rocketry, early astronauts, space missions, spacecraft through a vast archive of photographs, scientific facts, text, graphics and videos."