Jupiter Today | 22 August 2015 | Four Moon Alignment

Hello!  Many apologies for the couple of days I've missed this post.  Technical difficulties.

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.

Jupiter continues to move towards Superior Conjunction on 26 August.  Here's the current SOHO image showing the steady progress:

At 0h UTC, Io begins the day pretty much directly behind Jupiter moving east in quad 1.  Europa and Ganymede start the day transiting Jupiter together and moving west in quad 3.  Callisto will spend all day in quad 1 heading east.

By 6h UTC, Io is firmly in quad 1 moving east.  Europa and Ganymede are now firmly in quad 3 heading west.

At 12h UTC, Io has gone past its eastern elongation and is now in quad 2 moving west.

By 18h UTC, Io is about to begin transiting Jupiter, while Europa will soon be at its western elongation and moving into quad 4.

At 0h UTC tomorrow, Io has transited Jupiter and is now in quad 3 moving west.  Europa has just passed its western elongation and is now in quad 4 moving east.  Ganymede continues in quad 3.  Callisto will be in quad 1 for the next few days.

Io goes through an apojove at 19:27 UTC at a distance of 423,496.2 km.

At 0h UTC, Jupiter's position on Earth's celestial sphere is RA 10h 17m 30.4s, DEC +11d 32m 56.7s.  The phase angle today is 0.708 degrees, which is 0.137 degrees less than yesterday.  The angular separation between Jupiter and the Sun is 3.772 degrees, which is 0.729 degrees less than yesterday.  The distance between Jupiter and the Sun is 805,873,154 km, which is 36,696 km further away than yesterday.  Jupiter is moving away from the Sun at a velocity of 1,529.0 km/h, which is 5.667 km/h slower than yesterday.  Jupiter is 956,814,462 km away from Earth, which is 170,357 km further away than yesterday.  Jupiter and Earth are moving away from one another (mainly due to Earth's motion around the Sun) at a velocity of 7,098.2 km/h, which is 1,294.209 km/h slower than yesterday.  We continue to decelerate as we move towards Superior Conjunction on the 26th of the August.

From 00:30 to 04:08 UTC, Ganymede transits Jupiter.  From 00:51 to 04:26, the shadow of Ganymede transits Jupiter.  At 00:31 Io reappears from Jupiter's shadow.  Europa will end its transit of Jupiter at 01:42 UTC, and Europa's shadow will end its transit at 01:51 UTC.  Io transits Jupiter from 19:25 to 21:44 UTC, and Io's shadow follows from 19:30 to 21:48 UTC.

For the final reported satellite mutual event of this very active 2015 season, Ganymede will occult Europa from 20:45 to 20:57 UTC.  This 12.2 minute event has an impact parameter of 0.731 arc seconds -- a shallow occultation.

The Glorious Orbital Ribbons:

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.

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Please send me your feedback, comments, and questions to jupitertoday AT gmail DOT com or the comments section of this blog.

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.