Image of Jupiter with new dark spot in the southern polar regions, captured by Anthony Wesley on July 19, 2009 at 1554UTC from Murrumbateman, Australia. Click to embiggenate.
The big news today (July 19) is that Jupiter seems to have a dark spot in its south polar region. The first images, posted by Australian amateur observer Anthony Wesley, ripped around the Web at the speed of light and have caught everybody’s attention. Is this dark spot a storm? Evidence of some weather event stemming up from the lower atmosphere? An impact site?
The best way to tell would be image the planet in infrared, which I’m sure is happening as I write this. There are a number of infrared-enabled observatories that probably can look at this thing as a “target of opportunity.”
Regardless of what it is, observers will watch this thing as it rotates around the planet over the next few days to see track changes in its size and appearance.
This does look reminiscent of the impact sites created when pieces of Comet Shoemaker-Levy 9 smashed into the Jovian cloud tops in 1994. As more astronomers look at this thing and follow its progress, we will certainly figure out whether or not this is an impact or a very cool new atmospheric feature forming in the upper cloud decks of the planet. Either way, it’s a great find for Anthony and a boon for planetary observers around the world.
How many times have been sitting around on a Sunday wondering if you’d ever get a chance to see Jupiter and its moons transit this close to the Sun just as a coronal mass ejection occurred? Well, here’s your chance, thanks to NASA’s STEREO-B spacecraft and its track of the Jupiter system as it sailed just 0.1 from the limb of the Sun last week. Eventually it disappears behind the occulting disk in the camera, but it was a heckuva pass while it lasted.
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Turns out these kinds of close approaches happen a lot and the STEREO gallery has a collection of images for you to peruse — including a larger version of this little “transit” movie. For Jupiter fans, this is a great look at the planet, since right now it’s too close to the Sun from Earth’s perspective to observe it from the ground. The STEREO (Behind) COR1 coronagraph had a good view and so it imaged Jupiter and its four major moons over a 30-hour period. If you look carefully, you can identify three of its moons close to Jupiter, and watch as their positions change over time. Those with keen eyes can see the fourth moon, Callisto, as a fainter object well to the right of the others. In this movie, Jupiter itself is largely saturated (overexposed), but the long exposure brings out the moons and the faint solar corona. The solid dark green area on the right is the coronagraph’s occulting disk. It blocks out the Sun and some of its bright atmosphere so that the spacecraft’s instruments can make out fainter structure just beyond the Sun. The thin, white line inside of that indicates the actual size of the Sun. As you watch the scene unfold, a coronal mass ejection sends a huge white cloud of charged particles out into space.
Thanks to Mark for sending me the link to the Spaceweather.com page that first posted the links to these neat STEREO files!
