This article will highlight what’s happening at Jupiter during August, 2009 – including when and where you can observe Jupiter, opposition date, and dates and times for other interesting events for observers and imagers, such as the Wesley Impact Scar and Galilean Moon mutual events (occultations and eclipses).

Jupiter reaches opposition on August 14th, 17:10 GMT/UT, where it will be 4.0278 Astronomical Units (AU) from Earth. Opposition is when Jupiter, the Earth and the Sun form a straight line and Jupiter and the Sun are 180° apart from our viewing location. This means that Jupiter rises in the East when the Sun sets in the West, and sets in the West when the Sun rises in the East.

Jupiter is very easy to find during the month of August, as it is the brightest “star” in the evening sky, shining brilliantly at -2.9 apparent magnitude. It rises in the East just after sunset and is overhead at around midnight.

For telescope observers and imagers, Jupiter is the biggest and brightest it’s been in years – subtending 49" (arcseconds), making it a great target for high-resolution astrophotographers.

The Wesley Impact Scar is still visible in August, and is stretching out and changing every day. It may be your last chance to see it before it disappears for good, so make sure you head out and observe it while you can. If you’re observing the GRS, the impact scar transits 2 hrs and 6 minutes after the GRS – so when the GRS is setting, the impact scar will be rising and both can be visible at the same time.

Use the table below for impact scar transit times during August. You will need to convert the GMT to your local timezone, and then check whether a) it is dark at that time, and b) what altitude Jupiter will be at that time.

Wesley Impact Scar Transit Times (time it crosses the middle of the disc)

DATE (GMT)   HH:MM   HH:MM   HH:MM
01/08/2009   11:37   21:32
02/08/2009   07:28   17:23
03/08/2009   03:19   13:14   23:10
04/08/2009   09:06   19:01
05/08/2009   04:57   14:52
06/08/2009   00:48   10:44   20:39
07/08/2009   06:35   16:30
08/08/2009   06:26   12:21   22:17
09/08/2009   08:13   18:08
10/08/2009   04:04   13:59   23:55
11/08/2009   09:51   19:46
12/08/2009   05:42   15:37
13/08/2009   01:33   11:28   21:24
14/08/2009   07:20   17:16
15/08/2009   03:11   13:06   23:02
16/08/2009   08:58   18:53
17/08/2009   04:49   14:44
18/08/2009   00:40   10:36   20:31
19/08/2009   06:27   16:22
20/08/2009   02:18   12:13   22:09
21/08/2009   08:05   18:00
22/08/2009   03:56   13:51   23:47
23/08/2009   09:43   19:38
24/08/2009   05:34   15:29
25/08/2009   01:25   11:21   21:16
26/08/2009   07:12   17:07
27/08/2009   03:03   12:59   22:54
28/08/2009   08:50   18:46
29/08/2009   04:41   14:37
30/09/2009   00:32   10:28   20:24
31/08/2009   06:19   16:15

Mutual Events

Every 6 years, the Earth passes through Jupiter’s equatorial plane. 2009 happens to be such a year. As a result, this year we get to see some fantastic mutual moon events – where the Galilean Moons have occultations and shadow transits with each other. Here’s an example of an occultation I captured back in May 2009.

To observe or photograph these events, it’s best to plan for it because an event may only occur every few days at any time during that day. Use the table below to check for events during August. You will need to convert the GMT to your local timezone, and then check whether a) it is dark at that time, and b) what altitude Jupiter will be at that time.

Terminology

• An Eclipse is when the shadow of one Moon eclipses another Moon. Eg: “Io Eclipses Ganymede” means Io’s shadow will cover part or all of Ganymede.
• An Occultation is when one Moon passes in front of another Moon. Eg: “Io Occults Europa” means Io will pass in front of and cover part or all of Europa.

Eclipses

DATE(UT)         BEGIN TIME  END TIME   EVENT
Year  Mon. Day   Hour Min.   Hour Min.
2009   8    1    17   38.1   17  46.9   Io Eclipses Ganymede
2009   8    3    15   53.4   16   3.1   Io Eclipses Europa
2009   8    4    21   44.1   22   1.5   Ganymede Eclipses Europa
2009   8    5    19   37.3   19  43.6   Ganymede Eclipses Io
2009   8    7     5   10.0    5  20.4   Io Eclipses Europa
2009   8    8    20   38.0   20  47.6   Io Eclipses Ganymede
2009   8   10    18   27.4   18  38.6   Io Eclipses Europa
2009   8   12     1   42.7    2   3.4   Ganymede Eclipses Europa
2009   8   14     7   47.5    7  59.8   Io Eclipses Europa
2009   8   15    23   47.4   23  58.4   Io Eclipses Ganymede
2009   8   16    16   24.4   17   9.0   Io Eclipses Ganymede
2009   8   16    20   22.8   21   8.4   Io Eclipses Ganymede
2009   8   17    21    9.1   21  22.8   Io Eclipses Europa
2009   8   19     6    0.2    6  25.7   Ganymede Eclipses Europa
2009   8   20    17   42.0   18   2.2   Ganymede Eclipses Europa
2009   8   21    10   35.3   10  50.8   Io Eclipses Europa
2009   8   22     4   36.3    4  50.0   Io Eclipses Europa
2009   8   23     3   15.2    3  29.5   Io Eclipses Ganymede
2009   8   24     1   21.6    1  35.4   Io Eclipses Ganymede
2009   8   25     0    5.6    0  23.9   Io Eclipses Europa
2009   8   25    18    8.1   18  21.0   Io Eclipses Europa
2009   8   26    10   54.1   11  29.5   Ganymede Eclipses Europa
2009   8   27    22   41.5   22  55.5   Ganymede Eclipses Europa
2009   8   28    13   46.9   14  10.4   Io Eclipses Europa
2009   8   29     7   35.5    7  47.8   Io Eclipses Europa
2009   8   30     7   40.9    8  13.9   Io Eclipses Ganymede
2009   8   30    12    4.1   12  50.0   Io Eclipses Ganymede
2009   8   31     4   56.4    5   4.3   Io Eclipses Ganymede

Occultations

DATE(UT)         BEGIN TIME    END TIME   EVENT
Year  Mon. Day   Hour Min.    Hour Min.
2009   8    3     16  26.3     16  35.5   Io Occults Europa
2009   8    4     22  48.1     22  56.9   Ganymede Occults Europa
2009   8    7      5  33.2      5  43.1   Io Occults Europa
2009   8   10     18  40.2     18  50.9   Io Occults Europa
2009   8   12      2   4.9      2  16.5   Ganymede Occults Europa
2009   8   14      7  49.0      8   0.6   Io Occults Europa
2009   8   15      0  25.4      1   8.1   Io Occults Europa
2009   8   16     16  57.3     17  31.8   Io Occults Ganymede
2009   8   17     20  58.3     21  10.9   Io Occults Europa
2009   8   18     14  25.3     14  48.7   Io Occults Europa
2009   8   19      5  32.1      5  47.4   Ganymede Occults Europa
2009   8   21     10  10.3     10  24.3   Io Occults Europa
2009   8   22      3  59.4      4  17.4   Io Occults Europa
2009   8   24     23  23.7     23  39.3   Io Occults Europa
2009   8   25     17  22.1     17  37.4   Io Occults Europa
2009   8   26      9  15.8      9  36.5   Ganymede Occults Europa
2009   8   28     12  41.8     12  59.7   Io Occults Europa

For a more comprehensive list, use the Astronomical Almanac Online.

Happy Observing! I’d love to hear about your reports and see your images.

Article by Mike Salway (iceman). Discuss this article on the IceInSpace Forum.