Switching on the fall season

Wow, it is almost like someone, somewhere, threw a switch and the daytime temps are cooler and the nighttime temps have dropped drastically, down into the 50s already.

I know we still have some warm weather ahead of us, but, it is becoming more and more obvious that a seasonal change is coming.

That change, from summer to autumn, officially happens on Friday, Sept. 23, at 3:05 a.m. MDT, when the sun crosses the celestial equator headed south.

Here in the northern hemisphere we are headed for cooler temps, but our friends in the southern hemisphere are warming up and headed into spring.

With the change of seasons comes a change in the sky as well.

The summer stars are holding on to their position directly overhead, but with each passing day they slip a little further to the west and the autumn stars are rising earlier each day headed for their place of prominence.

The premier group of autumn stars is what I call the Perseus group. The constellations that tell the story of Perseus, the hero, Pegasus, the flying horse, Andromeda, the fair damsel in distress, Cassiopeia, the bragging mother, and Cepheus, the king who really didn't do too much.

Let's not forget Cetus, the sea monster. But, he joins the festivities later.

I think we all pretty much know the story already so let's get to the sky.

First up is one of the largest of the constellation, Pegasus, the Flying Horse. Look east about an hour after sunset for a large diamond shape, or a square tipped up on one end.

That is the body of the horse. Now, for some reason he is depicted upside down with his front legs going up and his neck and head down to the lower right, plus we only see the front half of him.

Andromeda herself is represented by two lines of stars extending from Alpheratz, the left-most star of the square (or in this case diamond shape) of Pegasus, out to the left toward Perseus, the Hero. Almost like two arms reaching out toward him.

Perseus is a group of stars just rising in the northeast taking the shape of a capital "A," and Cassiopeia is above Perseus with her famous "W" shape.

While he doesn't do much in the story, Cepheus, the King, can be found even further up, above Cassiopeia. He takes the shape of what a child would draw for a house, two lines for sides and two lines for a roof. Only here, our good king is lying on his side with the point of the roof very near, and pointing at, the North Star, Polaris.

That will get you started. Go out each evening and locate the constellation to familiarize yourself with where they are and in future columns we will discuss each constellation separately.

SKY WATCH:

Full moon, Monday, Sept. 12, at 3:05 a.m. MDT. This is the "Harvest Moon" as it is the full moon closest to the autumnal equinox. For you early risers, grab your binoculars and head outside and look for tiny Mercury about a half-hour before sunrise. Mercury will be in the same field of view with Regulus, the brightest star in Leo, the planet is the brighter of the two. Regulus is also called the point on the reverse question mark of Leo's head and mane. They can be seen together until Saturday.

NEXT WEEK:

Pegasus, the Flying Horse, and more astronomical blathering.