Chemical element named mendelevium in honor of D.I. Mendeleev, the first to arrange the elements in a periodic manner. Most recently, the synthesis of element 118 (since named oganesson) was reported in October 2006, and the synthesis of element 117 (tennessine) was reported in April 2010. Ten materials familiar to various prehistoric cultures are now known to be chemical elements: Carbon, copper, gold, iron, lead, mercury, silver, sulfur, tin, and zinc. Three additional materials now accepted as elements, arsenic, antimony, and bismuth, were recognized as distinct substances prior to 1500 AD. Phosphorus, cobalt, and platinum were isolated before 1750. Most of the
SN 2003gd SN 2003gd, and which is believed to be the supernova's progenitor star. This progenitor star was a red supergiant, consistent with the expectations of existing single-star stellar evolution models. It is the first progenitor of a normal type II-P supernova to have ever been detected. SN 2003gd SN 2003gd was a type II-P supernova occurring in the spiral galaxy Messier 74 in the constellation Pisces. SN 2003gd was discovered on 12 June 2003 by Robert Evans, using a 0.31m reflector, and its discovery was confirmed on 13 June 2003 by R. H. McNaught using the 1.0m telescope at the Siding