Planetary Satellites

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id="main_content" tabindex="-1" class="container-fluid hide-tabindex">   <noscript> <div class="alert alert-danger"> <h4>Please enable JavaScript for this website.</h4> <p> This website makes extensive use of JavaScript. The top menus will not function without it and most tools will also not work. </p> <p> If you do not know how to enable JavaScript in your web browser, you should be able find instructions by searching the web for "enable javascript in my browser" (or similar). </p> </div> </noscript> <h1 class="no-top-margin">Planetary Satellites</h1> <h3> What is a planetary satellite?</h3> <p>Naturally-formed bodies in orbit around planets are referred to here as “planetary satellites”, and are often called “moons.” Planetary satellites (as well as the primary planet) orbit the planetary system barycenter, the combined center of mass of the planet and all of the moons in that planetary system. The barycenter, in turn, orbits the Sun. The Sun, in turn, orbits the center of the Galaxy, an orbit which, as of yet, is not available on <a href="/horizons/">Horizons</a>. The best-known planetary satellite is, of course, Earth’s moon, eponymously named — before any other planetary satellites were known — “the Moon”. Currently, we know of no planetary satellites in orbit around Mercury or Venus. All the other planets have at least one known planetary satellite.</p> <h3>Description of Menu Items</h3> <table class="table table-hover"><thead><tr><th>Page</th><th>Description</th></tr></thead><tbody><tr><td><a href="/sats/orbits.html">Orbits & Ephemerides</a></td><td>Provides access to orbital data for all known planetary satellites.</td></tr><tr><td><a href="/sats/phys_par/">Physical Parameters</a></td><td>Table of selected physical parameters for planetary satellites.</td></tr><tr><td><a href="/sats/obs_data.html">Observational Data</a></td><td>Provides sets of observations that are currently being used in the creation and improvement of JPL's planetary satellite ephemerides.</td></tr><tr><td><a href="/sats/discovery.html">Discovery Circumstances</a></td><td>Discovery circumstances for known planetary satellites.</td></tr></tbody></table>  <div id="footer" class="container-fluid footer"> <div class="row"> <div class="col-sm-5 col-xs-12"> <img class="ssd-logo" src="/images/ssd_logo.png" alt="SSD Logo" /> </div> <div class="col-sm-3 col-xs-12"> <div class="link-inv"> <a href="/sitemap.html"><i class="fa-fw fa fa-list-alt"></i> Site Map</a> </div> <div class="link-inv"> <a href="https://www.jpl.nasa.gov/caltechjpl-privacy-policies-and-important-notices"><i class="fa-fw fa fa-user-secret"></i> Privacy</a> </div> <div class="link-inv"> <a href="https://www.jpl.nasa.gov/jpl-image-use-policy"><i class="fa-fw fa fa-picture-o"></i> Image Policy</a> </div> </div> <div class="col-sm-4 col-xs-12"> <div class=" link-inv"> <a href="/contact/"><i class="fa-fw fa fa-envelope"></i> Contact Us</a> </div> <div class="text-smaller"> <span class="footer-label text-nowrap">Site Manager:</span> <span class="text-nowrap">Ryan Park</span> </div> <div class="text-smaller2"> <span class="footer-label text-nowrap">Site Design:</span> <span class="text-nowrap">Alan B. 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Planetary Satellites