Countdown to the Autumnal Equinox

Wednesday, September 2, 2015

September, wow, where has the year gone? Sort of like watching the stars and constellations pass overhead from east to west.

In three weeks we will be observing the Autumnal Equinox -- the beginning of autumn -- and a few days later a total lunar eclipse. Talk about anticipation.

Well, if the seasons are changing, so are the constellations. Directly overhead tonight will be the Summer Triangle, to the south are Sagittarius and Scorpius, the consummate constellations of summer.

To the north is the ever-present, non-seasonal Big and Little Dippers, and to the west all we can see of spring is the tail of Leo, the Lion sinking below the horizon. If you want to see winter, you will need to be an early riser because Orion is rising at about 3:30 am MDT.

But, to the east we see what is coming -- autumn.

Find a nice dark-sky place that has an unobstructed view of the eastern horizon about an hour after local sunset. Bring a comfortable lawn chair, some liquid refreshment (preferably non-alcoholic), some munchies, and let's begin to explore.

Directly in front of us is the Great Square of Pegasus, the Flying Horse. We call him "The Great Square," but right now he is more like a great baseball diamond standing up on one corner.

If we are going to imagine a flying horse just remember, he is upside down with his legs sticking up, his head to the right, his front legs to the left and the hindquarters are not seen.

The star he is standing on is Algenib, Arabic for "The Flank." Most of the named stars in Pegasus are Arabic in nature. The Arabs were great astronomers and many of the ancient Greek astronomers used their information when considering the stars.

It is really strange, a constellation with a history in a Greek myth with Arabic names.

Going clockwise the next star in the diamond is Alpheratz, which is joint star with Andromeda, two strings of stars leading off to our left toward the constellations Perseus (the location of the Andromeda Galaxy). In Arabic it means "The navel of the mare." Since it is also part of Andromeda it can be referred to as "The head of the maiden."

On top of the diamond is Scheat, Arabic for "Horse's Shoulder," which is appropriate because this is where the two bands of stars for the horse's front legs extend, and lastly, on the bottom corner is Markab, Arabic for "Something to ride, or saddle."

It is from this star that the neck and head of the horse extend to the right.

That is quite a line-up for a baseball team.

SKY WATCH: Third-quarter moon, Saturday, Sept. 5. If you are an early riser on the fifth, look for the moon almost overhead. It is close to Aldebaran in Taurus, the Bull at about 5:30 am MDT.

Saturn and Mercury are the only planets visible in the western sky. The ringed-planet is about 20 degrees (two clenched fists held at arms length) above the southwestern horizon about an hour after local sunset.

Mercury is above the western horizon very close to where the Sun went down and may need binoculars to locate in the Sun's glow. Look about a half-hour after local sunset. Venus has made an entry in our morning sky and can be observed shining very brightly just to the right of Mars. Keep watching Mars and Venus each week because in late October they will have a spectacular meeting with the giant Jupiter.

NEXT WEEK: Venus dances with the moon, stars, and planets, and more astronomical blathering.

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