At least two amateur astronomers were aiming their telescopes at Jupiter on March 17 and caught what appears to be an asteroid hitting the planet, causing a bright explosion.
John McKeon was filming Jupiter with his 11-inch telescope in Swords, Ireland, while Gerrit Kernbauer was doing the same with a 8-inch telescope in Mödling, Austria.
“The seeing was not the best, so i hesitated to process the Videos. Nevertheless 10 days later i looked through the Videos and i found this strange light spot that appeared for less than one second on the edge of the planetary disc,” Kernbauer wrote in the description of his video on Youtube.
“Thinking back to Shoemaker-Levy 9, my only explanation for this is an asteroid or comet that enters Jupiters high atmosphere and burned up/explode very fast,” he wrote.
“Shoemaker-Levy 9” refers to a comet that broke apart and struck Jupiter in 1994.
Even though the March 17 impact seems like just a spark on the video, it would have been rather monumental up close, considering how gigantic Jupiter is compared to Earth.
Still, the asteroid probably wasn’t very large. “[P]robably in the tens-of-meters wide range,” wrote Phil Plait, author and astronomer who runs the Bad Astronomy blog.
But Jupiter has much stronger gravity than Earth so objects are pulled to it with much greater power, making the impact that much more explosive.
“On average (and ignoring orbital velocity), an object will hit Jupiter with roughly five times the velocity it hits Earth, so the impact energy is 25 times as high. The asteroid that burned up over Chelyabinsk, Russia, in 2013 was 19 meters across, and it exploded with the energy of 500,000 tons of TNT,” Plait explained.
“Now multiply that by 25, and you can see how it doesn’t take all that big a rock to hit Jupiter for us to be able to see it from Earth,” he said.
“Incidentally, at these huge speeds, hitting the atmosphere is like slamming into a wall. A lot of people get understandably confused how an asteroid can explode due to air, but the pressures involved as it rams through the atmosphere at these speeds are ridiculously huge,” he continued.
“The air and rock heat up, the rock starts to fall apart, and each chunk then gets hot, and so on, creating a very rapid cascade that releases the energy of motion in just a second or two,” he wrote.