What’s Up In the Sky Oct’ 08
There are times when I wish I could go back in time and talk to someone famous. It is a silly fantasy, the assumption is you could understand one another. Language has changed, be it Italian, German, or English or any other language, it has evolved. Still after reading about "horseshoe orbits," I would like to sit down with Isaac Newton. Since he didn’t seem to tolerate fools, I imagine our conversation would be brief, and I may have left out the word very.
Still it fastinates me that the Earth has possibly three objects, or more, in "horseshoe orbit" around it, and Saturn has two. Earth’s two natural companions asteroid 3753, Cruithne, and 2002 AA29. Depending upon the source, both objects have been described as temporary moons of Earth and yet they aren’t either.
The best way I can describe a "horseshoe" orbit is to take your thumb and index finger and make the letter "C". In the opening imagine a pea size Earth. The Sun is in the center of the "C".
Two things to remember. 1. Objects near the Earth, but between the Earth and Sun are orbiting faster. 2. Objects on the other side of Earth still close to Earth, but further from the Sun, orbit slower.
The two asteroids are in orbits around the Sun similar in time to Earth, 365 days, but have more eccentric orbits. Here’s the good part, as they approach Earth on an inside orbit it is going fast enough to pass us from behind. However, Earth’s gravity accelerates it causing it to pass behind Earth and go into the higher, outer orbit where it begins to slow down and the Earth begins to leave it behind. At some point in time, Earth approaches these objects from the rear. Now our gravity causes them to decelerate and cross in front of us, where they fall into the inside orbit, begin to accelerate and pull away from us. Thus, the cycle begins again.
This has triggered all sorts of reports of the Earth or Moon being struck by these asteroids. We have no idea how long they have been doing this, or how long they can do it, or what could influence a change. They are, for now, in a stable orbit around the Sun. A "horseshoe" orbit only is apparent when they are mapped.
Now it’s time to reveal the third object: On November 14, 1969, Apollo 12 was launched. The third stage rocket booster circled the Earth in the ’70s. It was captured by the Sun’s gravity, flew away from Earth to orbit the Sun, and returned in 2002. It maybe in a "horseshoe" orbit.
Saturn has two small moons, Epimetheus and Janus, that approach each other every four years. One in a higher orbit and one in a slightly lower one. The moons are about the same size. As they approach each other their gravity interacts causing them to swap orbits.
Oct 6/7 The Moon will be near Jupiter these two nights. To the west, and low, on the 6th. to the east
on the 7th, which is also first quarter Moon.
14 Full Moon.
17 The Moon passes in front of the Pleiades in the early morning sky.
Look for Mercury in the early morning sky, just above the horizon 45 min before sunrise. It
can be seen through the 30th.
21 Last quarter Moon. Also, the Orionid meteor shower. The Moon will interfere.
23/25 Waning crescent Moon will be in the area of Regulus and Saturn.
25/26 Venus passes north of Antares low in SW at twilight.
28 New Moon
29 The asteroid Vesta is opposite the Sun.
31 The thin crescent Moon s near Antares and Venus in the SW at twilight.
