Touring The Evening Skies
July 11, 2017


I was talking with some friends the other day when one of them asked, "Would somebody please just tell me what season it is?" We all laughed, and we all knew what he meant: the weather seems to go from the upper 80's to the lower 70's at the drop of a hat - in the day time! One week it feels like the middle of summer and the next it feels like the beginning of spring and then back again. Well, in spite of what it feels like it is definitely summer. You might not know it from the daytime high temperatures over the past few weeks, but we passed the summer solstice back on June 20, so warmer, humid days are coming. And that is fine with me! I love being out under the stars any time, but I especially like to enjoy them wearing just a light jacket instead of a snowmobile suit, so bring on the summer weather!

Let's begin our tour of bright, naked-eye planets. Jupiter will be in the southwestern sky all month, hanging out in the constellation Virgo, just to the west of the brightest star in that constellation; Spica. At the beginning of July, around 9:30 PM, Jupiter will be about 35 degrees off the horizon almost due southwest. At about the same time on the 15th, Jupiter will have moved slightly towards the west-southwest and will have dropped to about 28 degrees off the horizon. By the 29th the King of the Planets will have moved even more towards the west-southwest and will be just a little more than 20 degrees off the horizon. Be sure to take some time to view Jupiter through a telescope this month. Jupiter never disappoints when it is seen through a telescope of almost any size.

Next on our list of bright evening planets is my favorite: Saturn. If you've been reading my articles for any length of time, you already know that viewing Saturn through the little 50mm Sears refractor I got for my birthday is what got me hooked on astronomy. Seeing that soft yellow ball with those incredible rings really made an impression on me and I'm not the only one, either. I never get tired of showing people Saturn through my telescope at star parties and watching their reactions. Some people walk around to the front of the telescope to make sure I don't have a picture or little model suspended inside the dew shield. Kids are usually impressed by Saturn but their parents are ALWAYS impressed by it. Maybe kids have seen so many of the incredible images sent back from space probes like Cassini that they just aren't that impressed by the small images from most amateur telescopes. Their parents, on the other hand, realize just how far away Saturn really is and how amazing it is that we can see those sharp, beautiful rings and subtle cloud bands so clearly even through a small telescope.

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is closest to us when it is at opposition which happened back on June 15. Close is kind of a relative term. Even though at opposition it is 'closer' than at other times we are still more than 746 million miles apart! Saturn is classed as a gas giant. It has a diameter of 72,367.4 miles which is more than 9 times the diameter of Earth. It has only one-eighth the average density of Earth, in fact if you could place Saturn in a huge ocean it would float!

Saturn's pale-yellow color comes from ammonia crystals in its upper atmosphere. You might think it is windy here in Iowa, but our winds don't even come close to the winds on Saturn where windspeeds can reach 1,118 miles per hour. That's higher than on Jupiter, but not as high as those on Neptune.

Saturn's beautiful ring system is made up of nine continuous main rings and three discontinuous arcs. They are composed mostly of ice particles with a smaller amount of rocky debris and dust. Saturn has 62 moons. This does not include the hundreds of moonlets that make up the rings. Titan, Saturn's largest moon, and the second-largest in the Solar System, is larger than the planet Mercury, although it is less massive, and it is the only moon in the Solar System that has a substantial atmosphere.

If you are an early riser, you no doubt have noticed brilliant Venus shining in the Eastern sky before sunrise. The Moon will pay a visit to Venus on July 20 passing just 3 degrees above her. Mercury is visible all month but it is very low in the west just after sunset. At the beginning of the month Mercury sets about 9:45, about 55 minutes after sunset. As July draws to a close, Mercury will set at about 9:37, about an hour and 5 minutes after the sun. Unfortunately, Mercury stays very close to the horizon and by the time the sky is dark enough to see it, it is too close to the horizon and gets lost in the treetops and clouds.

One last thing: I hope you are making plans to see the total eclipse on Monday, August 21. I'm sure there will be lots of coverage in the newspapers and on TV. It will only be partial here in Iowa, but just a little way into Missouri or over into Nebraska it will be total. It would definitely worth taking a day off to travel a little ways to see. We'll talk about it more next month. Until then, clear skies!


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