JUPITER TODAY: 31 July 2015 | Three Perijoves

Good Day!

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:

Jupiter System 31 July 2015

This is a view of the Jupiter system looking down on it.  The blue line is the line of sight to Earth, while the gray line 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 System Earth POV 0h UTC

At 0h UTC, Io begins the day in quad 3 moving west.  Europa starts the day in quad 2 moving west.  Ganymede is also in quad 2 moving west and will be transiting Jupiter today.  Callisto begins the day in quad 3 moving west and will be going through its western elongation today.

Jupiter System Earth POV 6h UTC

By 6h UTC, Io is very near its eastern elongation and will be moving into quad 4 heading east.  Europa and Ganymede continue in quad 2 moving towards transit.  Callisto is still in quad 3 moving west.

Jupiter System Earth POV 12h UTC

At 12h UTC, Io is now firmly in quad 4 moving east.  Europa is in quad 2 near transit.  Ganymede is transiting Jupiter.

Jupiter System Earth POV 18h UTC

By 18h UTC, Io is moving behind Jupiter and into quad 1 heading east.  Europa and Ganymede have both transited Jupiter and are now in quad 3 moving west.  Callisto has moved past its western elongation and is now in quad 4 heading east.

Ganymede is at perijove at 01:00 UTC at a distance of 1,069,228.534 km.  Europa is at perijove at 18:40 UTC at a distance of 664,487.055 km.  Io moves through perijove at 18:45 UTC at a distance of 420,023.696 km.  Notice again that the perijoves of Europa and Io are at the same time on opposite sides of Jupiter.

Quite a few Jupiter-Satellite events today.  From 11:09 UTC to 14:47 UTC, Ganymede transits Jupiter.  Ganymede's shadow transits Jupiter from 12:54 UTC to 16:29 UTC.  From 14:28 UTC to 17:20 UTC, Europa transits Jupiter.  This means that from 14:28 UTC to 14:47 UTC, Ganymede and Europa are both seen transiting Jupiter.  The shadow of Europa transits Jupiter from 15:18 UTC to 18:09 UTC.  Io moves behind Jupiter at 16:07 UTC.  Finally, Io reappears from Jupiter's shadow at 18:50 UTC.

There are no satellite mutual events today.

Here are the orbital ribbons for today:

Orbital Ribbons 31 July 2015

Jupiter RA 09h 59m 22.6s, DEC +13d 11m 56.4s.  The phase angle today is 3.712 degrees, which is 0.132 degrees less than what it was yesterday.  The angular separation between the Sun and Jupiter as seen from Earth is 20.071 degrees, which is 0.745 degrees less than what it was yesterday.  The distance between Jupiter and the Sun is 805,053,646 km, which is 37,967 km further away than what is was yesterday.  This gives a radial velocity of Jupiter relative to the Sun of 1,581.958 km/h moving away.  The distance between Jupiter and Earth today is 946,005,496 km.  That's 833,653 km further away than yesterday, which translates into a radial velocity of 34,735.542 km/h moving away from one another.

Did you have any idea we were moving so much and so quickly?

Even though Jupiter is near Superior Conjunction (taking place on 26 August 2015), please send me your pictures of Jupiter!  If you do, I'll post them to this blog!  Please also include the time (in UTC if possible) you took the image, the telescope you used, the camera you used, and any other information you might think is useful.

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?

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.