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>According to <a href="">NASA scientists</a>, the Voyager 1 spacecraft entered interstellar space in August 2012, becoming the first spacecraft to leave the <a href="/our_solar_system/solar_system.html&edu=high&dev=1">solar system</a>. The space probe is about 19 billion km from the <a href="/sun/sun.html&edu=high&dev=1">Sun</a>.  <a href="/space_missions/voyager.html&edu=high&dev=1">Voyager 1 and 2</a> were launched in 1977 on a <a href="/space_missions/voyager.html&edu=high&dev=1">mission</a> that flew them both by <a href="/jupiter/jupiter.html&edu=high&dev=1">Jupiter</a> and <a href="/saturn/saturn.html&edu=high&dev=1">Saturn</a>, with Voyager 2 continuing to <a href="/uranus/uranus.html&edu=high&dev=1">Uranus</a> and <a href="/neptune/neptune.html&edu=high&dev=1">Neptune</a>. Voyager 2 is the longest continuously operated spacecraft. It is about 15 billion km away from the <a href="/sun/sun.html&edu=high&dev=1">Sun</a>.<p><small><em>Image courtesy of NASA</em></small></p>Scientists are concerned that melting Arctic sea ice will increase the amount of fresh water in the <a href="/earth/polar/arctic_currents.html&edu=high&dev=1">Beaufort Gyre</a>, which could spill out into the Atlantic and cause major climate shifts in North America and Western Europe. Watch the <a href="/earth/changing_planet/freshwater_arctic.html&edu=high&dev=1">Changing Planet: Fresh Water in the Arctic video</a>.<p><small><em> Courtesy of Jack Cook, WHOI (<a href="">Woods Hole Oceanographic Institute</a>)</em></small></p>This image is a montage of high resolutions photographs of the Earth taken in January 2012 by the Visible/Infrared Imager Radiometer Suite (VIIRS) instrument on the Suomi NPP satellite.  The image shows many stunning details of <a href="">our home planet</a> - <a href="">particularly at high resolution</a>. The beauty of our planet is obvious from space - our blue <a href="">waters</a>, our white <a href="">clouds</a>, and the green from <a href="">life</a> abundant at the surface.<p><small><em>Image courtesy of NASA</em></small></p>A <a href="">study</a> of over 40,000 written entries in Irish Annals and ice core measurements shows a strong correlation between <a href="">volcanic eruptions</a> and extreme cold weather in Ireland over a 1200 year period, from 431 to 1649.  During this time up to 48 volcanic eruptions were identified in Greenland ice core records through deposition of volcanic sulfate in annual layers of ice. Find out more about <a href="">volcanoes and climate</a>.<p><small><em>Image Courtesy of Marco Fulle</em></small></p>A group of
  Emperor penguins wait their turn to dive into the ocean near <a
  Island, Antarctica</a>
  on November 3, 2004.
Emperor penguins routinely dive to 500 meters in
  search of food. Scientists are interested in understanding how they can
  endure the stress of these dives in such an <a
  environment</a>.<p><small><em> Image courtesy of Emily Stone,   National Science Foundation</em></small></p>

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