Old photographs show no evidence of the above nebula. In 1992, a white dwarf star [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ] toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Cygnus [ http://www.astronomical.org/constellations/cyg.html ] blew off its outer layers in a classical nova [ http://observe.arc.nasa.gov/nasa/space/stellardeath/stellardeath_4a.html ] explosion: an event called Nova Cygni 1992 [ http://antwrp.gsfc.nasa.gov/apod/ap951227.html ]. Light flooded the local interstellar neighborhood [ http://www-ssg.sr.unh.edu/tof/Outreach/Interstellar/ ], illuminated this existing gas cloud, excited the existing hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ], and hence caused the red emission [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ]. The only gas actually expelled by the nova [ http://astrosun.tn.cornell.edu/SC10/ncyg92.html ] can be seen as a small red ball just above the photograph's center. Eventually, light from the nova shell [ http://www.journals.uchicago.edu/ApJ/journal/issues/ApJL/v448n2/5174/sc0.html ] will fade, and this nebula will again become invisible!