A look at the hero, Perseus

Monday, October 23, 2006

Now that we have looked at the horse he rode in on, and the pretty girl he saves, lets have a try at the hero, Perseus.

Perseus is sort of an "A" shaped constellation just left (as you are looking east) from Pegasus and Andromeda. It rises in the early evening and can be seen in the northeastern sky just after dark-thirty. Find Pegasus again, follow the two arms of Andromeda to the north as she "reaches" for the hero Perseus.

Most of the stars of Perseus are second and third magnitude (a degree of brightness); so should be visible even in a moderately light polluted town. The stars of Pegasus are also this bright.

There are a couple of interesting things to look at in Perseus. The first is the variable star Algol, or the Demon Star. Just in time for Halloween. It is the second brightest star in the constellation and is what astronomers call an eclipsing binary. That is a fancy name for a double star system where the fainter star in the pair passes in front of the other (from our line of sight) and causes the other to dim for a period of time.

In Algol's case that period is two days, 20 hours and 49 minutes, if you want to time it. It is possible to see the difference in the brightness of Algol if you watch it over a period of time and compare it with the surrounding stars. Algol is located about where the shin would be on the left leg of the constellation (on the right side as you are looking at it).

It got its name, Demon Star, when ancient astronomers noted the periodic dimming and brightening--it looked like an "eye" winking. For that reason it was associated with the eye of Medusa, the snaky-haired Gorgon that Perseus used to turn the sea monster to stone thus saving the pretty girl.

The other sight worth looking at in Perseus is the Perseus double star cluster. Binoculars will reveal some of the brighter stars in the clusters, making them a lovely sight from a dark place. You can see them without any aid, (they look like two fuzzy blobs) but use the binoculars.

The clusters are located above Perseus about halfway between it and Cassiopeia (the giant "W" we will talk about later). The stars in those clusters appear faint, but don't be fooled, some of them put out as much light in a minute as our Sun does in an entire year.

SKY WATCH: Wednesday, a two-day old Moon will be hanging around with Antares, the heart of the scorpion, again. Look for them together in the southwest at about 6:30 p.m. local time, the Moon will be to Antares' left.

Remember, Scorpius is a summer constellation and is rapidly leaving the evening sky. Speaking of summer, have you noticed the Summer Triangle is now moving off to the west in the sky and the autumnal constellations are in the overhead spot at about 9 p.m. local time? The Moon is at first quarter on Sunday, Oct. 29.

Next time, something completely different.

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