“Maybe some people don't feel scared when they think about comets and supernovas. Maybe they think it is wonderful.” -Lydia Netzer What, in our Solar System, has a long tail from boiled-off frozen ices? What simultaneously leaves an X-ray signature when the solar wind collides with those boiled-off atoms, kicking electrons out and causing X-ray emissions? If you guessed a comet, you'd be "traditionally" correct, beginning with Comet Hyakutake in 1996.