Comet Shoemaker–Levy 9 A of the nucleus entered Jupiter's southern hemisphere at a speed of about . Instruments on "Galileo" detected a fireball that reached a peak temperature of about , compared to the typical Jovian cloudtop temperature of about , before expanding and cooling rapidly to about after 40 seconds. The plume from the fireball quickly reached a height of over . A few minutes after the impact fireball was detected, "Galileo" measured renewed heating, probably due to ejected material falling back onto the planet. Earth-based observers detected the fireball rising over the limb of the planet shortly after the initial impact.
Comet ISON Central Bureau for Astronomical Telegrams identified the object as an asteroid, and it was listed on the Near Earth Objects Confirmation Page. Follow-up observations by independent teams were the first to report cometary features. Therefore, under the International Astronomical Union's comet-naming guidelines, Comet ISON was named after the team that discovered it, rather than the individual discoverers. After it was discovered in 2012, some media sources called Comet ISON the "Comet of the Century" and speculated that it might outshine the full Moon. An "Astronomy Now" columnist wrote in September 2012 that "if predictions hold true then Comet ISON will