What’s Up in the Sky August, 2009
By Peter Burkey
If you own a fairly decent, moderate sized telescope, and often find yourself in search of interesting things to observe, this month offers several rare opportunities. After being hit by a small asteroid or comet fragment the planet Jupiter has been in the news lately so let’s focus on it.
On the night of August 18-19, the four largest moons of Jupiter put on quite a show. Begin observing around 10:00 p.m. when you will find Jupiter rising in the southeast. It will be the brightest object in the sky so you should not have any trouble finding it. Pick a spot with a clear view of the horizon as it will be rather low at that time. Have faith, for as the night progresses it will become easier to observe.
In the telescope you should see all four moons lined up to the right of the planet. By 11:00 p.m., the nearest one, Io, will pass in front of the planet followed by its shadow 15 minutes later. Use a higher power to see if you can observe this phenomenon, called a “transit”.
Meanwhile, watch the next two moons out, Ganymede and Europa, close in on each other. At 1:19 a.m. Io emerges from the western (left) limb of the planet at which time Ganymede and Europa are moving closer and closer toward each other.
For a few minutes either side of 1:40 a.m., Ganymede passes in front of (occults) Europa and the two appear as a single point of light. But hold on, the best is yet to come. For a few minutes around 2:15 a.m., Europa fades and completely disappears as Ganymede’s shadow passes over it, creating a nearly total eclipse. Within a few minutes, Europa recovers its normal brightness, and the separation between the two gradually increases. This will be one of those rare opportunities to actually observe celestial objects in motion.
Then, on the night of August 26-27, you will have a chance to see the shadows of these same two moons fall on Jupiter simultaneously. Begin observing as soon as possible after the Sun sets and you should see one moon to the left of the planet and two to the right. By 10:00 p.m., the one on the left (Io) has disappeared behind Jupiter and the two on the right (Europa and Ganymede) have moved in front. Keep watching and you may be able to spot both shadows on the planet at the same time.
Remember, these observations require some knowledge of and skill in using an amateur telescope. Good luck.
This month in history:
August 5: Neil Armstrong born – 1930
August 12: Echo 1 launched – 1960
August 17: Phobos, moon of Mars, discovered by Asaph Hall – 1877
August 18: Cassini spacecraft flies by Earth – 1999
August 25: Voyager 2 flies past Saturn – 1981
August 27: Teacher in space program announced – 1984
Here are this month’s viewing highlights:
Planets this month: Jupiter at opposition on the 14th – up all night. Saturn is low in W at dusk. Venus rises 3 hrs. before sunrise and dominates eastern predawn sky.
August 5: Full Moon.
August 9: Saturn’s rings are edge-on to the Sun.
August 11-12: Perseid meteor shower.
August 13: Last quarter Moon.
August 14: Moon occults Pleiades; Jupiter at opposition.
August 20: New Moon
August 27: First quarter Moon.