Jupiter Today | 07 August 2015 | Europa and Ganymede Transit

Hello!

JUPITER TODAY is a daily blog about the dynamic Jupiter system for the purpose of monitoring activity.

We start with the overall view of activity with the Jupiter system, showing the orbits of the four Galilean moons:

This is a view of the Jupiter system looking down on it.  Following the blue line to the left is the line of sight to Earth, while following the gray line to the left is the line of sight to the Sun.  The orbits of the four Galilean moons are shown.  The large dots indicate the position of each moon at 0h, 6h, 12h, 18h, and 24h (0h the next day) UTC for this date.  From this point of view, the moons revolve around Jupiter in a counter-clockwise motion.  For more information about this graphic, see the post from 30 July 2015.

At 0h UTC, Io begins the day in quad 3 having just transited Jupiter.  Europa is just past its eastern elongation and is now in quad 2 moving west.  Ganymede is also in quad 2 moving west.  Callisto spends all day in quad 1 moving east towards eastern elongation which will happen tomorrow.

At 6h UTC, Io is in quad 3 moving west.  Europa and Ganymede continue in quad 2 moving west.  Europa is "catching up" to Ganymede and will pass it while both are transiting Jupiter.

By 12h UTC, Io has moves past its western elongation and is now in quad 4 moving east.

At 18h UTC, Io is moving behind Jupiter, going into quad 1 moving east.  Europa and Ganymede are transiting Jupiter and moving into quad 3 going west.

By 0h UTC tomorrow, Io is firmly in quad 1 moving east, Europa and Ganymede have now transited and are in quad 3 moving west.  Callisto continues in quad 1 moving east.

Three perijoves today!  At 11:35 UTC, Ganymede goes through a perijove at a distance of 1,069,255.8 km.  Europa and Io go through their perijoves at the same time!  Europa's distance is 664,483.9 km and Io's distance is 420,025.6 km.

At 0h UTC, the position of Jupiter on Earth's celestial sphere is RA 10h 05m 05.9s and DEC +12d 41m 11.8s.  The phase angle today is 2.770 degrees, which is 0.136 degrees less than yesterday.  The angular separation between Jupiter and the Sun as seen from Earth is 14.865 degrees, which is 0.743 degrees less than yesterday.  The distance between Jupiter and the Sun is 805,317,219 km, which is 37,650 km greater than yesterday.  This gives a radial velocity between Jupiter and the Sun of 1,568.75 km/h, which is 3.083 km/h faster than yesterday.  The distance between Jupiter and the Earth today is 951,025,756 km, which is 629,120 km greater than yesterday.  This gives a radial velocity between Jupiter and the Earth of 26,213.333 km/h moving away from one another, and this is 1,230.542 km/h slower than yesterday.  So while the two planets continue to move apart for a few more days (towards Superior Conjuction on the 26th of August), the velocity at which they are moving apart is slowing down.

From 15:36 to 19:14 UTC, Ganymede transits Jupiter.  From 16:53 to 20:29 UTC, the shadow of Ganymede transits Jupiter.  From 17:15 to 20:07 UTC, Europa transits Jupiter.  From 17:52 to 20:44 UTC, the shadow of Europa transits Jupiter.  At 18:08 UTC, Io moves behind Jupiter.  At 20:44 UTC, Io reappears from the shadow of Jupiter.

From 23:10 to 23:57 UTC, Ganymede occults Europa.  This is a 47.8 minute event with an impact parameter of 0.596 arc seconds.  So a pretty nice occultation.

Orbital ribbons for today;

Jupiter is so near Superior Conjunction (taking place at 22:00 UTC on 26 August 2015) that photography and other data collection isn't practical.  We'll have to wait about a months after SC to start viewing the Jupiter system again.

Spread the word about this daily blog!  This blog is subject to evolution.  What can I do to make this blog more interesting and more informative?

Subscribe at the right column of this blog and get these posts sent to you automatically!

Please send me your feedback, comments, and questions to jupitertoday AT gmail DOT com.

With my gratitude, the data used to create the orbit plots and ribbons was supplied by the JPL Horizons website.  The graphics showing the location of the four moons as seen from Earth are via 'Jupiter Viewer 2.8'.  Jupiter-Satellite and Satellite mutual events data is supplied from IMCEE.

Until tomorrow, I bid you Peace.