As Jupiter shines brightly during its 2014–2015 apparition, quite often Jupiter’s four big Galilean moons will occult and cast their shadows on each other. A “mutual events season” like this happens about every 6 years, when Earth and Sun cross the plane of the satellites’ orbits. We are now in the later part of this season, with these mutual events, still occurring thru August. Some of these events will dim the shadow-eclipsed moon, as seen here, or the combined light of two moons during a partial or total occultation. Photometric recordings of the events provide a very accurate way to refine the satellites’ gradually changing orbits. Their orbits are morphing in interesting long-term ways due to interactions among the satellites and between them and Jupiter. Occult Watcher can obtain mutual events through the “Planet Satellites (Global)” feed under “Configuration / Prediction Feeds”.
The event illustrated above occurred on April 27 at 2300 hrs, PDT. The shadow from the Jovian moon Io was cast upon the surface of Europa as viewed from earth. The accompanying light curve shows the apparent drop in brightness during the eclipsing event. The total event was approximately 4 minutes in length out of the nearly ten minutes of recording time.
This particular video was further analyzed by Tony George for accurate timing extraction. Data was then properly format and sent to the IMCCE in Paris for inclusion in this season’s Jovian moons mutual events data set.
A Reminder for RECON Teams: The video recording of these types of events will probably require some Mallincam camera setting changes to properly record a useable video. Teams are reminded that camera setting should be returned to the proper RECON occultation settings before a RECON campaign event.