Free Astronomy Magazine May-June 2015

ingly, on 17 March 1671, Anthelme real- izes, once again be- fore anyone else, that the star show- ed up again, to the point that on 30 April it reached mag +2.6, i.e., about twice as bright as the previous year. Hevelius notes its unexpected return only in late spring, when the star is also observed by Gio- vanni Domenico Cassini, who in that same year was ap- pointed director of the newly founded Paris Observatory. Towards the end of August, the star disappeared again from view, to then reappear one last time in March 1672, when it was rediscov- ered by Hevelius, who could observe it until 22 May, after which the star faded below the 6 th mag (average naked-eye limit). In this third appearance the star never became brighter than mag +5.5, and therefore went unnoticed to most observers. Besides the sky position and apparent brightness, the various witnesses of that triple event did not have the means to provide additional infor- mation for posterity, save for some contro- versial references to a reddish colour of the new star during the periods of lower bright- ness. Over the centuries, the appearance of that star became a distant memory, also because no one had until fairly recently been able to relate Nova Vul 1670 to the potential ce- lestial remains of cata- clysmic phenomena, and this despite the fact that already from the first half of the 20 th century astronomers knew that historical novae and su- pernovae leave traces in the form of nebulosity. Any attempt to discover something in the loca- tion of Nova Vul 1670 proved unsuccessful, in- cluding a research con- ducted in 1938 by Mil- ton L. Humason on pho- H evelius’ celes- tial map pub- lished in the scientific journal Philosophical Transactions of the Royal Society of London, with a circle around the location where the Nova Vul 1670 appeared. [Royal Society] The video on the left takes us on the border be- tween the con- stellations Cyg- nus and Vulpe- cula, where the “new” star ap- peared. [ESO/Dig- itized Sky Survey 2, N. Risinger]