Jupiter Today | 08 September 2015 | Apojoves and Perijoves

Hello!  Today, there are two apojoves and two perijoves.  An apojove is when a moon of Jupiter is furthest away, and a perijove is when it's closest.  In a 24 hour time period, we oftentimes see Io go through both an apojove and a perijove.  An interesting observation I've made is that the position of Io's apojove is almost directly on the opposite side of the planet from Europa's apojove, and of course this goes for their perijoves also.  This also means that Io's apojove and Europa's perijove are on the same side of the planet.  In any case, it's a very very cool resonance and I wonder what effects are being felt by these two moons and how does this resonance effect the other moons and Jupiter itself?  Curious.....

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 has moved out of the field of view of SOHO, so no more SOHO images until next superior conjunction.  Booooooooooooo!

Orbital Motion

The graph below shows the positions of the four Galilean moons over the next 24 hours as seen from Earth.  The curved lines show the path of each moon through time.  The dark band in the center is Jupiter.  The x-axis is the distance, in arc seconds, from the center of Jupiter:

At 0h UTC, Io starts the day firmly in quad 3 moving west.  Europa is just past eastern elongation and is now in quad 2 moving west.  Ganymede spends all day in quad 4 moving east and only at the end of the day does it move behind Jupiter.  Callisto spends all day in quad 1 headed east.

By 6h UTC, Io is just past western elongation and is now in quad 4 moving east.

By 12h UTC, Io is now firmly in quad 4 moving east.  Europa continues in quad 2 headed west.

At 18h UTC, Io has moved behind Jupiter and is now in quad 1 moving east.  Europa is transiting Jupiter and will be moving into quad 3 headed west.

By 0h UTC tomorrow, Io is in quad 1 moving east.  Europa is past transit and firmly in quad 3 moving west.  Ganymede is moving behind Jupiter.  Callisto continues in quad 1 moving east.

Apojoves and Perijoves

At 13:13 UTC, Ganymede goes through an apojove at a distance of 1,071,813.3 km.  At 13:25 UTC, Io goes through a perijove at a distance of 420,040.3 km.  At 13:42 UTC, Europa goes through a perijove at a distance of 664,522.2 km.  At 17:43 UTC, Callisto goes through an apojove at a distance of 1,896,585.1 km.

Relative Positions and Motions

At 0h UTC, the position of Jupiter on Earth's celestial sphere is RA 10h 31m 32.5s, DEC +10d 13m 21.4s.  The phase angle is 1.696 degrees, which is 0.138 degrees greater than yesterday.  The angular separation between Jupiter and the Sun as seen from Earth is 9.110 degrees, which is 0.751 degrees greater than yesterday.  The distance between Jupiter and the Sun is 806,488,169.7 km, which is 35,709.7 km greater than yesterday.  This means that Jupiter and the Sun are moving away from one another at a velocity of 1,487.9 km/h.  The distance between Jupiter and Earth is 954,979,414.2 km, which is 355,765.9 km closer than yesterday.  Jupiter and Earth are moving towards each other at a velocity of 14,823.6 km/h.  Wow.

Jupiter-Satellite Events

From 14:59 to 19:29 UTC, Io moves behind Jupiter.  From 17:25 to 20:16 UTC, Europa's shadow transits Jupiter.  From 17:50 to 20:41 UTC, Europa transits Jupiter.  From 22:49 to 03:18 UTC tomorrow, Ganymede moves behind Jupiter.

Glorious Orbital Ribbons

These are the spacial and temporal connections between the four Galilean moons.  Notice the I-E-G symmetry.  This is, once again, looking down upon the Jupiter system.

When is the first image of Jupiter after Superior Conjunction going to be taken?  If you have one, send it to me!

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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.