One day after Galileo, Simon Marius independently discovered moons around Jupiter, though he did not publish his discovery in a book until 1614. It was Marius’s names for the four major moons, however, that stuck—Io, Europa, Ganymede and Callisto.
This is so significant that scientists can already start doing science with it. If you look closely, Calisto (outermost moon) appears to be fainter and we are not sure why.
Juno spent nearly 5 years to get to Jupiter. The spacecraft successfully entered orbit around Jupiter on July 5th, 2016. This is just the beginning.
-Orbit Capture Phase- This first two orbits of Juno, Orbit 1 and Orbit 2, are Capture orbits. Their period is around 53 days and will involve some science in them, especially when Juno is at Perijove to get the required data from that unpresented distance to Jupiter.
In a couple of days, science instruments will turn on and will be calibrated to start taking images and data for analysis. During these orbits, scientists at NASA will have plenty of time to test its instruments, analyse the data that is coming from Juno, and decide on the next steps and what to focus on.
For orbit 2, it will be like orbit 1 with Apojove on Sep. 23rd and Perijove on Oct 19th except at this point Juno will fire up its engine again for 22 minutes for the Period Reduction Phase to reduce its orbital period from 53 days to 14 days for orbits 3 to orbit 36. This will include the bulk of Juno’s science data.
Google celebrated it with their own doodle
If you missed the Post JOI Briefing, you can watch it here