Ready or not, here comes fall

Well, the season is turning whether you are ready for it or not. Not only are the evenings becoming cooler temperature wise, I have another indicator of the impending arrival of autumn.

A few blocks from my house there is a very large cottonwood tree. When the seasons are about to turn, the topmost branches start to turn yellow making the tree look like it has yellow spots.

When I last checked there were about eight yellow spots in the top of the tree.

The southern stars of summer are drifting westward very fast and soon will be lost to sight in the early evening.

The other stars of summer, the Summer Triangle, are lolling overhead these cooling evenings, but they too are headed west and by December will be setting in the northwest.

But, not to worry. A whole new set of celestial items are now arriving from stage right. The Great Square of Pegasus is now halfway up the eastern sky by 9 p.m. MDT.

To find Pegasus look in the east. At this time of year it looks like diamond shape standing up on end. Next find its northeast corner star, Alpheratz, a star it shares with Andromeda where we will find one of the jewels of the sky, the Andromeda galaxy. One of our neighbors in the "Local Group" of galaxies.

The galaxy can be seen without any optical aid, but a pair of binoculars or a telescope will be of great assistance.

It is a spiral galaxy like the Milky Way and is seen almost edge-on so it will look a little long and somewhat flattened.

At about 9 p.m. MDT start with Alpheratz in Pegasus. From there follow the two trails of stars that seem to reach out like arms north toward Andromeda's hero, Perseus. He is the guy who got her off the rock and out of the jaws of the sea monster.

Count out two stars along the two star trails, go up (west) from that second star about the same distance as between the lines and look for a faint fuzzy. That is Andromeda. As I said, you don't need any optical aid, but you will need a very dark sky away from the lights in town.

Andromeda is the farthest thing in the sky you can see with just your eyes. It is about 2.2 million light years, or about 13.2 trillion miles away. That is 13 with 15 zeros behind it, give or take a few zeros.

Andromeda's other name is M31, or the 31st item on Mr. Messier's list of things that are not comets.

If you are a person that likes to put things on a worry list, here is one for you. Andromeda is traveling toward the Milky Way Galaxy at about 500,000 kilometers an hour and in about five billion years will crash into our galaxy. Now if that won't keep you up nights, I don't know what will.

SKY WATCH:

Third quarter moon Sept. 11. A slender crescent Moon plays touchy-face with Mars on Sunday, Sept. 13. At about 2 a.m. MDT they will be about two degrees apart just above the eastern horizon. A very slender crescent moon next moves on to hook-up with the Beehive Cluster in Cancer, the Crab on Tuesday, Sept. 15.

NEXT TIME:

More astronomical blathering.