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&dev=">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>A new study has found that <a href="/earth/Atmosphere/airpollution_intro.html&edu=high&dev=">pollution</a> from <a href="/earth/Atmosphere/particulates.html&edu=high&dev=">fine particles</a> in the air - mainly the result of burning coal or <a href="/earth/interior/eruptions.html&edu=high&dev=">volcanic eruptions</a> - can shade <a href="/earth/Life/cnidarian.html&edu=high&dev=">corals</a> from sunlight and cool the surrounding water resulting in reduced growth rates.  Coral growth rates in the Caribbean were affected by volcanic aerosol emissions in the early 20th century and by aerosol emissions caused by humans in the later 20th century.  For more information, see the <a href="http://www.exeter.ac.uk/news/featurednews/title_278202_en.html">press release</a>.<p><small><em>Image courtesy of Toby Hudson (Wikimedia Commons)</em></small></p>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>New observations by the MESSENGER spacecraft provide  support for the hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed (shown in red) polar craters. Areas where polar deposits of ice imaged by Earth-based radar are shown in yellow.<p><small><em>Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory</em></small></p>How did life evolve on <a href="/earth/earth.html&edu=high&dev=">Earth</a> during the <a href="/earth/past/Archean.html&edu=high&dev=">Archean</a>, when the <a href="/sun/sun.html&edu=high&dev=">Sun</a> was about 25% weaker than today?  The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html&edu=high&dev=">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.html&edu=high&dev=">greenhouse</a> gas concentration was the same as today.  <a href="http://www.manchester.ac.uk/aboutus/news/display/?id=10798">Researchers</a> studying the <a href="/physical_science/physics/atom_particle/isotope.html&edu=high&dev=">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html&edu=high&dev=">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html&edu=high&dev=">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html&edu=high&dev=">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=high&dev=">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p><p>The United Nations <a href="http://reliefweb.int/sites/reliefweb.int/files/resources/PAND_report.pdf" target="_blank">estimated</a> that between 1994-2015, there were 6,873 natural disasters worldwide, which affected 218 million people and claimed 1.35 million lives. </p>
<p>Check out the materials about natural disasters in <a href="/earth/natural_hazards/when_nature_strikes.html&edu=high&dev=">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>

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