Clouds, moon -- it's always something for the Perseids

Drat, and double drat! Clouds, the bane of all astronomers, had the sky socked in on the morning of Aug. 12, so there was no good viewing of the Perseid meteor shower, at least in this area.

Astronomers in the eastern part of the state told me their skies were no better. I would say we could wait until next year; but sadly, the moon will blot out the Perseids in 2009. It is always something isn't it?

Sure was hot the last week of July and the first days of August, with several days hitting 100+ temperatures. Being summertime, I guess it just does that at this time of the year. The ancient peoples (the Roman and Greek type) had an explanation (sort of) for the hot and humid weather: the "Dog Days of Summer."

The Dog Days consisted of a period of about 40 days starting about July 3 and continuing to about Aug. 11. That is when the "Dog Star" or Sirius -- the brightest star in the night sky and the head of the constellation Canis Major, the Big Dog -- would rise about the same time as the sun.

In ancient times (the Greeks and Romans again) it was thought Sirius added its heat to that of the sun resulting in hotter days.

The time frame of the Dog Days has changed over the centuries, due to a process called precession, or in its long-winded version, precession of the equinoxes. Like a spinning top gradually slowing down, Earth wobbles on its axis, which traces out a complete circle every 26,000 or so years. This also causes the starting points of the seasons (solstices and equinoxes) to shift as well with respect to the stars, hence "precession of the equinoxes."

At present the axis of the Earth is pointed in the general direction of Polaris, the North Star. At one point the axis pointed toward Thuban, a star in Draco, the Dragon somewhat between the Big and Little Dippers. In another few thousand years it will be pointed toward Vega, the brightest star in Lyra, the Harp.

Currently, the helical rising of Sirius -- the date on which it rises at the same time as the sun -- occurs in early August. At 8.7 light years away, Sirius is far too distant to add any significant heat to our atmosphere. So where does this almost insufferable heat and humidity come from? Well, it is summer, when the days are long and the sun is high in the sky.

SKY WATCH:

Third quarter moon, Aug. 23. Mercury and Venus, the two innermost planets of the solar system, make a close pair on Aug. 20 and continue together leaving Saturn behind as they move upward and to the left chasing Mars. The two will be deep in the glare of the setting Sun; binoculars will be necessary to find them, or at least to find Mercury. Venus may be bright enough to be seen without optical aid. The pair will catch up to Mars on Aug. 31 and make another close planetary grouping, the second of the month. On Sept. 1 the inner duo will be even closer together and will be joined by a very, very slender crescent moon. Mercury and Venus continue toward Mars making a very close conjunction on Sept. 10. However, it will be extremely close to the western horizon so there can't be any obstructions in that direction if you are going to see them. Here is an interesting question, what do we call the second New Moon of the month. If we have two Full Moons, the second one is called a Blue Moon. But, what do we call the second New Moon?

We will have the second one on Aug. 30, the first was on Aug. 1. If anyone has an answer, let me know.**

NEXT TIME:

More astronomical blathering.