<p><strong>On Saturday the moon (pictured over Lisbon, Portugal's Tagus River) made its closest approach to<a href="http://science.nationalgeographic.com/science/space/solar-system/earth.html"> Earth</a> in 18 years—making the so-called supermoon the biggest full moon in years. (Get the <a href="http://news.nationalgeographic.com/news/2011/03/110318-supermoon-earth-japan-earthquake-tsunami-science-space-biggest-full-moon/">full story of the supermoon</a>.)</strong></p><p>The monthly<a href="http://science.nationalgeographic.com/science/space/solar-system/full-moon-article.html"> full moon</a> always looks like a big disk, but because its orbit is egg-shaped, there are times when the moon is at perigee—its shortest distance from Earth in the roughly monthlong lunar cycle—or at apogee, its farthest distance from Earth.</p><p>Likewise, because the size of the moon's orbit varies slightly, each perigee is not always the same distance away from Earth.</p><p>Saturday's supermoon was just 221,566 miles (356,577 kilometers) away from Earth—making the supermoon about 20 percent brighter and 15 percent bigger than a regular full moon, said Anthony Cook, astronomical observer for the<a href="http://www.griffithobservatory.org/"> Griffith Observatory</a> in Los Angeles.</p><p>Before the supermoon, astronomer <a href="http://www.adlerplanetarium.org/researchcollections/research/researchers">Geza Gyuk</a> said, "Look for the full moon as it rises above the eastern horizon as the sun sets below the western horizon—it will be a beautiful and inspiring sight."</p><p>That's advice a lot of photographers, including National Geographic fans, one of whom contributed this picture, apparently took to heart.</p><p>(See more readers' <a href="http://ngm.nationalgeographic.com/myshot/search?keywords=supermoon">supermoon pictures</a>.)</p><p><strong>More Moon Pictures, Facts, and News</strong></p><ul class="bullets"><li><a href="http://photography.nationalgeographic.com/photography/photos/moons-and-sunsets-photo-gallery/">National Geographic Moon Pictures and Prints</a></li><li><a href="http://blogs.ngm.com/blog_central/2011/03/the-new-moon.html">New Moon Map From National Geographic</a></li><li><a href="http://ngm.nationalgeographic.com/1969/12/moon-landing/astronauts-text">1969 National Geographic Article on First Moon Landing</a></li><li><a href="http://news.nationalgeographic.com/news/2002/12/1218_021218_moon.html">Full Moon Effect on Behavior Minimal, Studies Say</a></li><li><a href="http://news.nationalgeographic.com/news/2010/01/100129-biggest-full-moon-2010-mars/">Year's Biggest Full Moon, Mars Create Sky Show (2010)</a></li><li><a href="http://science.nationalgeographic.com/science/space/space-exploration/moon-myth-quiz/">Moon Quiz</a><a href="http://news.nationalgeographic.com/news/2002/12/1218_021218_moon.html"></a></li><li><a href="http://news.nationalgeographic.com/news/2010/06/100614-moon-water-hundred-lunar-proceedings-science/">Moon Has a Hundred Times More Water Than Thought</a></li><li><a href="http://news.nationalgeographic.com/news/2010/12/photogalleries/101221-lunar-eclipse-2010-pictures-winter-solstice-december-20-nasa-space-science-pictures/">Moon Eclipse Pictures</a></li><li><a href="http://news.nationalgeographic.com/news/2010/11/101118-science-space-full-moon-electric-charge/">Full Moons Get Electrified by Earth's Magnetic "Tail"</a></li><li><a href="http://news.nationalgeographic.com/news/2010/04/100414-moon-magnetosphere-solar-wind/">Mini Magnetic Shield Found on the Moon</a></li><li><a href="http://news.nationalgeographic.com/news/2010/08/100819-science-space-moon-shrinking-scarps-cooling-lunar-orbiter/">The Moon Has Shrunk, and May Still Be Contracting</a></li><li><a href="http://news.nationalgeographic.com/news/2009/07/photogalleries/first-moon-photos-lunar-recon-orbiter/">Moon Pictures: Lunar Orbiter's First Pictures Released</a></li></ul><p><em>—With reporting by Andrew Fazekas</em></p>