By the looks of this video, Monday night would not have been a very jovial night to spend on Jupiter. Two amateur astronomers spotted a bright white flash for a few seconds just inside Jupiter's eastern limb, which was probably a fireball a hundred miles in diameter caused by an asteroid or comet impacting Jupiter's atmosphere. Ka-POW!
The impact was first seen in real time by amateur astronomer Dan Petersen, who was observing Jupiter at 6:35 AM in Texas using his 12-inch telescope and MK1 eyeball. Petersen estimated the size of the "bright white" fireball at about 100 miles in diameter, and it lasted between 1.5 and 2 seconds. After he posted about the event on a telescope forum, another amateur astronomer, George Hall, went back and checked out some movies he'd been recording of Jupiter at about the same time, and came up with the image above, taken from the video below.
It's not uncommon for Jupiter to get beat on by small and medium-sized comets and asteroids: several objects in the 10-meter range have been observed smacking into Jupiter in the last few years. Back in 1994, comet Shoemaker-Levy 9 sent a whole series of mile-wide fragments plowing into the gas giant at 134,000 mph, leaving scars that lasted for months. Jupiter has the misfortune to be very, very large and also located entirely too close to the asteroid belt, which means that it acts like a planetary vacuum of sorts, sucking all sorts of junk towards it with its massive gravitational pull. Sucks for Jupiter, but it's good news for Earth, since it means that a significant number of space rocks are boffing Jupiter instead of us.
Possibly the coolest thing about this event is that the only reason we know about it is because a guy named Dan in Texas was looking at Jupiter through a telescope when it happened. It wasn't NASA and it wasn't some giant telescope on top of a mountain somewhere, it was just an amateur astronomer who was lucky enough to see something really, really awesome. And amateur astronomers (a lot of them, plus the pros) will be carefully watching Jupiter in the next few days, looking to see if any evidence of the impact shows up in Jupiter's atmosphere.