Keeping track of the seasons with the stars
Thursday, October 11, 2012
One nice thing about the stars, they are always there and they keep coming back around again each year.
The ancients used them to determine plowing and planting time, harvest time, and when to expect seasonal changes long before the changes actually occurred.
For example, when the residents of ancient Egypt saw Sirius, the Dog Star, rising with the sun in what we now call August they knew the annual Nile River flooding was at hand.
Other ancient cultures also used the stars to predict when the seasons would change, when it was time to plant and when to harvest.
Now, I said all that to say this, our old friends from the mythological story of Perseus and Andromeda are back in the sky.
I am sure most everyone remembers the story of Perseus and Andromeda. She was the pretty daughter of Cepheus and Cassiopeia, king and queen of Ethiopia. When mommy bragged that her daughter was more beautiful than the Nereids, the daughters of Nereus, the sea god he sent a sea monster to ravage the kingdom.
As punishment it was commanded that Andromeda be chained to a rock as a sacrifice to the monster. Sort of an ancient version of the princess and the dragon.
You know the rest. Along comes Perseus just back from killing the Gorgon Medusa, he sees the beautiful princess and the evil sea monster, rescues said fair damsel, and turns the monster to stone with the snake-haired head of Medusa, and they all live happily ever after.
The storytellers would have us believe that all the characters were then placed in the sky to help us remember the story. However this could be a case of which came first, the chicken or the egg and the story came from observing the constellations.
For our sky tour let's start with Pegasus. Pegasus is the horse that flew our hero, Perseus, out to where he could slay Medusa and cut off her snaky-haired head. Perseus was also riding Pegasus when he saw Andromeda in trouble.
To see our flying horse go outside at about 8 p.m. local time. If you have access to a dark-sky place these observations will go better.
Look east about halfway up the sky for the Great Square of Pegasus, the Flying Horse. Although at this time of year he looks more like a baseball diamond standing up on one corner.
Technically, we only see the front half of the horse and he is upside down with his head to the right (as you are looking at it) and his front legs extending up.
SKY WATCH: New moon, Monday, Oct. 15. For the early-birds, Friday morning, Oct. 12, at about an hour before local sunrise, the moon will be next to bright Venus. This next one will be a little difficult. Wednesday, Oct. 17, about a half-hour after sunset look west for a very slender crescent moon about eight degrees to the lower right of Mars. The sun will still be washing out the sky so binoculars will help. On Thursday a slightly thicker crescent moon will be on the other side of Mars. If you put Mars at about the 2 o'clock position in the binocular field of view, Antares, the brightest star in Scorpius, will be at about the 7 position. If you find them, compare the colors of the two. Antares is also called the "Rival of Mars" because both have a reddish color.
NEXT WEEK: Two more characters from our story, Perseus and Andromeda. And more astronomical blathering.