Something You Have Never Seen Before
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.
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.