Amateurs Spot New Impact Flash at Jupiter

Did Jupiter just get smacked again? Amateur astronomer José Luis Pereira of Brazil just discovered a probable new impact at the gas giant on September 13th at around 22:39:30 UT (18:39:30 EDT). Weather conditions were poor at the time, but Pereira decided to search anyway for possible flashes with DeTeCt software. The free program, created by planetary observer Marc Delcroix, is a useful tool to check for transient events such as planetary impacts.

Despite poor conditions Pereira suspected something on his first video and ran DeTeCt to check it out. The program alerted him that there was a high probability that what he saw was indeed a collision. He immediately sent a message to Delcroix for confirmation.

If confirmed, it would be the tenth recorded impact at Jupiter since the first in July 1994, when fragments of sundered Comet Shoemaker-Levy 9 slammed into the planet and left a trail of prominent dark scars. That number includes a minor strike spotted by NASA's Juno probe on April 10, 2020.

Jupiter rotates rapidly, coming round in just under 10 hours. To find a potential dark spot in the impact's wake, you'll need to know its latitude and longitude. But because the planet isn’t a rigid body, its rotation rate varies some by latitude. Equatorial regions spin fastest and polar regions slower. That’s why three systems are used to determine a feature's longitude: System I for locations within 10° of the equator (for the current flash), System II for all higher latitudes, and System III to match the rotation of the planet’s magnetosphere and Jupiter’s official rotation rate. Often, all three longitudes will be given for completeness.

Pereira captured the flash at latitude –5.5° and longitude 105.7° (System I / L1), 83.3° (System II / L2), and 273.4° (System III / L3). To determine the current or a future Jovian longitude in either system, use the Arkansas Sky Observatory’s Jupiter Central Meridian site and input the desired UT time. Click here to convert your local time to UT.

Amateurs are encouraged to check any videos or photographs taken within 5 minutes of the impact time to confirm the event. I also hope you’ll be watching the site for any impact scar that might appear in the coming nights. Happily, a dark marking should stand out well against the pale Equatorial Zone.

This is a developing story. Updates are found below.

** Update September 15 — At least 7 observers independently saw or recorded the flash according to Marc Delcroix. That includes 1 from Brazil, 2 from Germany, 3 from France and 1 from Italy. You'll find the French videos and still photos here.

German amateur astronomer Harald Paleske also captured images of the impact through his 16-inch reflector. Despite poor seeing at the time, the 2-second-long flash is obvious. I've seen a rough estimate of 100 meters (328 feet) for the impactor's size. There are no reports of dark impact spots at this time.

** Update September 20, 2021

There are still no reports, either visually or photographically, of impact spots, however Romanian amateur Sandu Val Cosmin can add his name to the short list of amateurs who captured the flash. He was photographing the transit of Io at the time and noticed a "large, rapid spark" in his IR filter toward the end of the observation. He realized its importance the following day when the Brazilian amateur José Luis Pereira shared his captures of the impact.

Cosmin writes: "Although I am (at) the beginning of the exposures to the planets, being focused on the deep-sky pictures, I think I was very lucky to catch this event."

We agree. Congratulations to Cosmin and all the other amateurs who captured this amazing sight!