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Night Sky

May Night Sky

Mayl 2010 Night Sky

Moons of our solar system—Part II

—Charlie Christmann

[The chart is for May 15th at 10 p.m. MDT]

Last month, we explored some of the moons out to the planet Jupiter. This month, we look at those at Saturn.

Next up in the enormous moon count are the moons of Saturn, 62 at last count. Many are being discovered by the orbiting Cassini spacecraft. Dione, one of those discovered by Cassini, is an icy body. Its surface includes heavily cratered terrain (some craters are more than 60 miles across), moderately cratered plains, lightly cratered plains, and wispy material.

Enceladus is one of the innermost moons of Saturn and reflects almost 100 percent of the light striking its surface. Indications are that the interior of the moon may be liquid today.

Iapetus is one of the stranger moons of Saturn. Its leading side, as it orbits about Saturn, is dark, with a slight reddish color, while its trailing side is bright. The dark surface might be composed of matter that was swept up from space. The real reason is still unknown.

Mimas is the sixth closest moon to Saturn, but it is tiny, only about as long as the distance from Los Angeles to San Francisco. The main characteristic of Mimas is that it looks like the Death Star from Star Wars. This feature is an ancient impact that may have nearly destroyed the moon.

Titan is the largest moon of Saturn, and it has an atmosphere. The atmosphere of Titan is heavy, producing a surface pressure more than one and a half times that of Earth at sea level. It is made mostly of nitrogen, but has about a one percent concentration of methane. The temperature on the surface is very cold, about -300 degrees Fahrenheit. Trying to look through the atmosphere to see the surface is difficult because of thick smog layers. The smog is a result of sunlight interacting with hydrocarbons, and it forms much like smog forms on the Earth. You will also find clouds composed of liquid nitrogen and methane drops. It is speculated that Titan may be covered with hydrocarbon lakes or oceans made from methane and ethane. On Earth, this could be explosive, but there is no oxygen on Titan, which is needed to create fire. Although many of the organic chemicals thought to have been the precursors to life on Earth are present on Titan, it appears to be too cold for life as we know it to have evolved there.

Again, next month, we will learn more about the moons of Uranus and Neptune.

The Planets and the Moon

• If you want to see Mercury this month after its spectacular conjunction last month with Venus, you’ll need to look just before sunrise in the east. Using binoculars, with care not to look at the sun, will help find it in the twilight.

• Venus is still shining bright in the western sky after sunset. Look 30 minutes after sunset on the 15th for a beautiful two-day old waxing crescent Moon-Venus conjunction.

• Look for Mars in the west southwest after sunset. On the 19th, two hours after sunset, find Mars in the constellation Leo. It will be just above the Moon. Castor and Pollux will be to the right and just slightly below Mars. Venus will be almost on the horizon. Regulus and Algieba are to the left and slightly above Mars. Further right and a bit higher will be Saturn.

• Jupiter rises in the early morning this month. Look about 4 a.m. early in the month and 2:45 a.m. late in the month to see it rise in the east. On Mother’s Day, May 9, look for a Moon-Jupiter conjunction one hour before sunrise, low in the east.

• Saturn is in the southwest after sunset. On the 22nd, two hours after sunset, find Saturn and the Moon hanging together in the southwest.

• The Moon is new on the 13th and full on the 27th.






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