Astronomy Picture of the Day

Explanation: Difficult to capture,this mysterious, squid-shapedinterstellar cloud spans nearly three full moons in planet Earth's sky.Discovered in 2011 by French astro-imagerNicolas Outters,the Squid Nebula'sbipolar shape is distinguished here by the telltale blue emission fromdoubly ionized oxygen atoms.Though apparentlysurrounded bythe reddish hydrogen emission region Sh2-129,the true distance and nature of the SquidNebula have been difficult to determine.Still, one investigationsuggests Ou4 really does lie within Sh2-129 some 2,300 light-years away.Consistent with that scenario, the cosmic squidwould represent a spectacular outflow of material driven by atriplesystemof hot, massive stars, cataloged as HR8119,seen near the center of the nebula.If so, this truly giant squid nebula would physically be over 50 light-years across.