Jupiter has taken a beating recently.
Two asteroids were seen crashing into the planet in September and October. They were only a month apart. Although it is not the first time such a spectacle has been seen, it is rare for observers to spot one. This can help us learn more about the solar system. It's thrilling to know that a small piece of the universe just exploded in space and time on the largest planet of the solar system.
Space.com: "These fireballs can be very rare, and they are very difficult for being observed just by chance," Ricardo Hueso (an astronomer at the University of the Basque Country, Spain) said. "This year was exceptional, because we normally discover one of these impacts approximately every two years."
Hit after hit
Because of Jupiter's size, even though it is rare, chances of seeing an impact on Jupiter are much higher than any other planet in the solar system. Jupiter is the biggest target and has the strongest gravitational pull in the area, which increases its impact rate in comparison to smaller worlds.
Amateur astronomers can often spot many of these impacts. Amateur astronomers are able to see the flashes even with small telescopes, but professionals usually cannot afford high-powered telescopes.
However, the most recent impact was discovered in part by Ko Arimatsu, a professional astronomer from Kyoto University in Japan. He often uses a telescope trained to Jupiter. Arimatsu shared his surprise when he discovered the flash impact through Space.com via email. "The impact rate is higher than I expected, or I was lucky to find it quickly," Arimatsu said in an email.
Hueso also noted that Arimatsu was able to see the event in two wavelengths. This gave scientists more information about the energy released as well as the mass of the impactor. This is a much more thorough observation than what amateurs usually can.
Other observations were even more fortunate. NASA's Juno mission orbiting Jupiter, which has been there since 2016, flew over the exact spot of the impact 28 hours later. Hueso stated that the Juno camera took a photo of the area of atmosphere from just a little over 1,200 miles (2,000 km) above the clouds.
Hueso stated that there is no trace of the atmosphere in the image. "So again, this object is small enough that any Jupiter-releasing material has been dissipated in the atmosphere and diffused by the environment winds within a few hours."
Hueso stated that the September impact was exceptional for more reasons than its timing. It was also the most observed event for this type of event and the brightest fireball flash at Jupiter.
He said that it was the largest object we had seen impacting the Earth and producing a fireball, but that it wasn't large enough to cause any damage in the planet's later hours or days.
Scientists are unable to see objects that are smaller or farther away as they try to find them. Scientists are simply not able to spot objects smaller than a few meters in diameter that orbit Jupiter's orbit. This orbit is at least 350,000,000 miles (560 million km) away from Earth.
Arimatsu stated that it was impossible to observe objects larger than a meter beyond the main belt. Therefore, their number is unknown. Jupiter is a natural "detector" for tiny objects. The occurrence rate, brightness and frequency of impact flashes are critical to understanding their size.
It is difficult to even estimate how many objects there are. Hueso stated that although we don't know the number of millions of such objects in the solar system, we do know that there are tens to millions or hundreds of million of them.
However, it is possible to track impacts at Jupiter. Hueso currently estimates that about 20 objects impact Jupiter each year. However, this does not include objects that strike the poles or far sides of Jupiter. The flashes that signal the death of these space rocks are still one of the few methods scientists have to study the smallest asteroids.
Hueso stated, "This is the only method that we have to see these objects." We can either observe them when they hit an object and create a crater or flash of light on Jupiter or when they are very, very close to Earth.
Leave a mark
One of the most well-known impacts on Jupiter was the 1994 Shoemaker-Levy 9 impact, which saw 19 fragments from a comet. Scientists were able to spot the object before the planet's gravity could break it apart, and then watch the fragments fall on their own.
Hueso stated, "I recall that the first time I connected the internet it was to search for images of the comet which was going to collide"
Although the Shoemaker-Levy 9 pieces reshaped the astronomy field, they also left their marks on Jupiter. They left behind a dark spot in the clouds that was larger than Earth, visible for many months. This was the result of the debris from comet fragments' atmospheric explosions gradually dissipating, and mixing with the outer layers of the clouds.
Hueso considers this trace one of the main reasons to be interested Jupiter impacts. He said that these objects had been impacting Jupiter for hundreds of millions of year, and "they are bringing various types of material to Jupiter's atmosphere, in some way they are contaminating Jupiter's atmosphere."
It's rare that such an impact leaves such a visible scar. Shoemaker-Levy 9 remains the most significant impact scientists have ever seen at Jupiter. It is also one of very few impacts that left visible traces less than a few hours after the collision. Scientists have not seen any scarring since 2009, despite compelling new observations.
"That was the last. Hueso stated that none of the impactors discovered since then has left any trace in the atmosphere. "Not from Earth at all."
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