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September is a transition period for the night sky as the constellations for summer change into those that can be seen in fall and winter. For example, September is about the last good month to find a dark site where you can easily see the Milky Way. I had a chance to visit my brother in California for a brief time and we went to a very dark site in the desert -- the Milky Way was outstanding! But ... I could see that in September and October, the Earth will move along its orbit in such a way that seeing our galaxy edge on will soon not be possible in the evening. The constellations of winter are coming.

Venus, Jupiter, Saturn and Mars will still be well placed for convenient observing in the evening. They will be displayed across the southern part of the sky, all pretty much along a line stretching from the west (Venus) to Mars, in the southeast. If you have been looking at Mars, you have noticed how bright it is. It is in the southeast as darkness comes on, but, because of the Earth's rotation, it will be in the south late and it is up all night. However, Mars will fade in brightness as September comes. This is because the Earth has a shorter orbit around the Sun and it will "pull away" from Mars as time moves on. This will make Mars' apparent brightness dimmer. Think of two racing cars speeding along on a track. The car that has the inside lane has a shorter distance to go around the track so it can move ahead of the other car in the outside lane and get around the track faster.

I have been disappointed in Mars this year because, just as the distance between Earth and Mars diminished, I had expected to be able to see Mars well. However, this planet developed a planet-wide dust storm and surface details that might otherwise be visible, even in my small telescopes, were obscured. My brother owns a large telescope, 18 inches, and when I visited him, I made an image of Mars. I figured that if there was any detail to be seen, it would certainly be easy to see it in an 18 inch. Nope! Mars still looks like an orange billiard ball, even in that great instrument.

If you look directly south in September, around 9 p.m., you can see one of my favorite constellations, Sagittarius. The ancient Greeks saw this star pattern as a centaur with a bow and arrow. These days, most people see this constellation as a teapot with "steam" rising from the spout. I urge you to find Sagittarius on your search engine and I think you will see what I mean. You might also find Scorpio the scorpion on your browser. Scorpio lies further west of Sagittarius. You will see that this constellation really does look like a Scorpion, complete with claws and a stinger.

Sagittarius is best seen under dark skies. If you see it that way, the "steam" coming out of the spout of the teapot is actually a very dense part of the Milky Way that lies in line behind the stars of Sagittarius. The stars that form the outline of the teapot are relatively close -- perhaps a few hundred light years. However, the "steam" that looks as if it is coming out of the teapot is made up of stars that lie about 5,000 to 8,000 light years away. (Just for fun, multiply 5,000 by 6 trillion. This number will give you the approximate number of miles you would have to travel to reach the stars that look like "steam." Take your lunch if you are traveling there!) They are so far away that they cannot be resolved with the naked eye and they make a starry haze behind the stars of Sagittarius.

Soon we will be back on Standard Time. It will get dark earlier than when we are on Daylight Time. The advantage to this, for amateur astronomers, is that we can see the dark sky earlier in the evening by clock time. The disadvantage is that if you have to set your telescope up from scratch, as I do, you have to get with it or face telescope assembly in the dark. This is not pleasant.

Sometimes, but certainly not always, the steadiest and most transparent air comes in the fall. This is a great time to look at the night sky because much of the haze that can form during the summer goes away and one can see more, even with the naked eye. However, you have to make up your mind to get out and look. The night sky show is free and there are no special effects -- it is all real!

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Dr. David Cater is a former faculty member of JBU. Email him at Opinions expressed are those of the author.

Community on 09/05/2018

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