Amateur astronomers spotted a 2-second burst of light along the eastern limb of Jupiter. Now it's a wait-and-see watch to find out if the planet sports an impact scar at the site.
|Update, Sept. 12: It's been two days since a pair of amateur observers spotted a fireball in the atmosphere of Jupiter (described below). However, nothing has been observed where the object hit. Apparently the impactor was too small to penetrate deeply into the Jovian upper atmosphere. According to John Rogers, Jupiter Section Director for the British Astronomical Association, "Several observers have now gotten excellent images on the second and third rotations after the fireball, and there is nothing new nor distinctive at the impact site."|
It's a good time to be viewing Jupiter. The King of Planets shines big and bright in the late-night sky — and that means lots of eyeballs and cameras are trained on it around the world each night from roughly midnight to dawn. All that scrutiny paid off early on the morning of September 10th, when two amateur astronomers captured a brief but dramatic flash in Jupiter's midsection near its eastern limb.The first report came from Dan Petersen of Racine, Wisconsin, who was watching before dawn with a 12-inch Meade LX200 telescope and a bino-viewer. Working at 400× he spotted a bright 2-second-long flare at 11:35:30 Universal Time September 10th along Jupiter's eastern limb, just inside the southern edge of the planet's dark North Equatorial Belt. He estimated the flare to be about 6th magnitude and located at +12° in latitude and 335° in System I longitude, though an analysis of Hall's image by S&T's Sean Walker yields values closer to +0.5° and 340°.
"I was thinking about imaging Jupiter this morning but decided to observe it instead," Petersen notes in a post to CloudyNights.com. "Had I been imaging I'm sure I would have missed it between adjusting webcam settings and focusing each avi ."
Petersen's report quickly reached the Association of Lunar and Planetary Observers and the British Astronomical Association, and from there it went out to a network of professional observers. Everyone hoped for an image to confirm his sighting, and that came from George Hall of Dallas, Texas. Observing from his driveway — and also using a 12-inch Meade LX200 telescope — Hall had captured the flash in his CCD video camera. He has posted a 4-second-long clip of the impact video.
It's not yet clear whether the flare, likely from the impact of a small comet nucleus or asteroid, will leave behind a dark "powder burn" in the planet's upper atmosphere. Similar blasts in July 2009 and June 2010 left little for observers to watch afterward. Based on Hall's image, planetary astronomer Imke de Pater (University of California, Berkeley) believes the fireball was much like the one seen in 2010 — "extremely interesting, but most likely without any debris."But that doesn't mean you shouldn't look! Jupiter's midsection spins every 9 hours 50.5 minutes (referred to as the System I rotation period) — slightly faster than the rotation rates of regions well away from the equator (System II) or the planet's interior (System III). This would have put the impact's location roughly centered on the disk on September 10th at 23:00 UT, though Sky & Telescope has not received word of any confirmations during that window. It was centered again on September 11th around 9:02 UT (favoring North America) and again at 18:52 UT (eastern Europe and western Asia).
Further predicted times of the site's central-meridian crossings: (times and dates in Universal Time): Sept. 12, 4:43, 14:33; Sept. 13, 0:24, 10:14, 20:05; Sept. 14, 5:55, 15:46; Sept. 15, 1:36, 11:27. To get Eastern Daylight Time, subtract 4 hours from the UT time.
The impact site is closer to Jupiter's central meridian than to the limb for 50 minutes before and after these times. Jupiter rises around 11 p.m. local daylight-saving time (depending on your location), is well up by a couple hours later, and dawn becomes too bright around 6 a.m. daylight time (depending on your location).
This event marks the sixth time that we have seen something slam into Jupiter, beginning with a fireball recorded by Voyager 1 as it flew past in 1979 and the celebrated impact of Comet Shoemaker-Levy 9 in 1994. "Even if this flash ends up being 'just a meteor'," Franck Marchis (SETI Institute) writes in his blog about the event, "it is remarkable that amateur astronomers are today capable of monitoring almost permanently the planet Jupiter."