Anti-crepuscular rays are beams of sunlight that appear to converge on a point opposite the sun. They are similar to crepuscular rays, but are seen opposite the sun in the sky. Anti-crepuscular rays are most frequently visible near sunrise or sunset. This photo of anti-crepuscular rays was taken at sunset in Boulder, Colorado. Crepuscular rays are usually much brighter than anti-crepuscular rays.<p><small><em> Image Courtesy of Carlye Calvin</em></small></p>Stars don't last forever. Occasionally, a star bigger than our Sun will end its life in a huge explosion, called a <a href="/the_universe/supernova.html&edu=high">supernova</a>. The center of the star collapses in less than a second, blowing away the outer layers of the star.  There are many beautiful images of supernova remnants, the expanding shell of gas made up of the outer layers of the original star. This image is the Vela Supernova Remnant.<p><small><em>Image courtesy of the Anglo-Australian Observatory/Royal Observatory Edinburgh</em></small></p>This historic image is the first ever taken from a spacecraft in orbit about <a href="/mercury/mercury.html&edu=high">Mercury</a>, the innermost planet of the solar system.  Taken on 3/29/2011 by <a href="/space_missions/robotic/messenger/messenger.html&edu=high">MESSENGER</a>, it shows numerous craters across the <a href="/mercury/Interior_Surface/Surface/surface_overview.html&edu=high">surface</a> of the planet.  Temperatures there can reach over 800F because Mercury is so close to the Sun and rotates so slowly.  MESSENGER entered orbit around Mercury earlier in March 2011.<p><small><em>NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington</em></small></p><p>You don't normally see <a href="/space_weather/space_weather.html&edu=high">space weather</a> forecasted on the evening news, but it does impact life on <a href="/earth/earth.html&edu=high">Earth</a> in many ways. What are the threats posed from all of these natural disasters and how can we work to mitigate those threats beforehand? </p>
<p>Check out the materials about natural disasters in <a href="/earth/natural_hazards/when_nature_strikes.html&edu=high">NBC Learn Videos</a>, and their earth system science connections built up by the related secondary classroom activities.</p><p><small><em>NBC Learn</em></small></p>There are over 900 <a href="/the_universe/uts/megalith.html&edu=high">rings of stone</a> located in the British Isles. The most famous of these stone rings is of course, <a href="/the_universe/uts/stonehenge.html&edu=high">Stonehenge</a>.    The stones of Stonehenge were put in place between 3,000 B.C and 2,000 B.C. by neolithic people.Some speculate that the site was built as a temple of worship of the ancient Earth deities. Some say it was used as an <a href="/the_universe/uts/stonehenge_astro.html&edu=high">astronomical observatory</a> of sorts. Still others say it was a burial ground.<p><small><em>  Image courtesy of Corel Photography.</em></small></p>An <a href="http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc000905e.php">8.6 magnitude earthquake</a> struck on 11 April 2012 off of Banda Aceh, Sumatra, Indonesia, followed by a strong aftershock.  Earthquake motion was primarily horizontal.  A tsunami warning was issued for the Indian Ocean, but was cancelled at 12:36 UTC.  A tsunami was observed at 1 meter or less. Find out more about <a href="/earth/geology/quake_1.html&edu=high">earthquake</a> and <a href="/earth/tsunami1.html&edu=high">tsunami</a> processes. Check out the resources <a href="/teacher_resources/2011_AGU-NESTA_GIFT_Workshop.html&edu=high">here</a>.<p><small><em>NOAA</em></small></p>

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