When amateurs Anthony Wesley and Christopher Go simultaneously videorecorded a bright flash on Jupiter last June 3rd, it drove home the startling realization that such events probably occur — and are observable — more often than anyone had imagined.
Well, guess what? Based on a video captured by a Japanese amateur astronomer, it's just happened again! Masayuki Tachikawa was observing Jupiter early on the morning of August 21st (18:22 Universal Time on the 20th), when his video camera captured a 2-second-long flash on the planet's disk. The location was along the northern edge of Jupiter's North Equatorial Belt, roughly at 17° north and System II longitude 140°.
News of the flash reached astronomer Junichi Watanabe (National Astronomical Observatory of Japan), who posted details and an image on his blog.
Tachikawa, who lives in Kumamato City on the island of Kyushu, was observing with a Philips ToUcam Pro II attached to his 6-inch (150-mm) Takahashi TAO-150 f/7.3 refractor with a Tele Vue 5× Powermate. You can view the (south-up) video here — thanks to Daniel Fischer for providing this link.
Whatever caused this flash, it's not a glint from an orbiting satellite. "After announcement of the flash to Japanese community," Watanabe told me via email, "another amateur astronomer looked back his data taken independently — and found the flash exactly at the same place at same time."
Tokyo amateur Kazuo Aoki posted an image here and his video here. Notably, Aoki has refined the moment of impact to within a second of 18:21:56 UT. He was using a Celestron 9¼-inch telescope and a Philips ToUcam Pro video camera.
The two observers were separated by some 500 miles (800 km), ruling out something near Earth as the cause.
Word from Isshi Tabe, who's coordinating reports about this event for the Association of Lunar and Planetary Observers in Japan, is that a third sighting was made by Masayuki Ishimaru. He was using a Borg 125SD f/6 refractor and a 30-frame-per-second video camera in Toyama City, about 160 miles northwest of Tokyo. You can view Ishimaru's video here.
Interestingly, at the time cloudy weather prevented both Chris Go and Anthony Wesley from observing Jupiter. According to John Rogers (British Astronomical Association), observers report nothing at that location one Jupiter rotation prior to the event time. Watching the planet two rotations afterward, Phillipine observer Tomio Akutsu found no trace of the possible impact; French observer Marc Delcroix also saw nothing in a series of images from the ultraviolet to near-infrared.
As luck had it, Imke de Pater (University of California, Berkeley) and Heidi Hammel (Space Science Institute) were in the midst of a two-night Jupiter run using the Keck II telescope in Hawaii when the strike occurred. "Judging from the position we definitely observed that region," de Pater says, "but we didn't notice anything anomalous at the telescope." They'll look over the images more carefully once they return home. "The solar system just is a busy place!" Hammel quips.
To Jupiter specialist Glenn Orton (Jet Propulsion Laboratory), the flash looks like another June 3rd event. "Perhaps the time has come," he adds, "to establish a worldwide network of Jupiter-monitoring telescopes so that the planet can be watched 24/7."