Rising early for something special

As I have mentioned before, I am not a morning astronomer, unless there is something really worth getting up for. Well, for the next couple of weeks I will be up early looking for something I have heard about but have never seen. It is an elusive quantity that requires the joining of the right lighting, the right timing, and a clarity of sky.

This sight is known by several names, the "false dawn," and the "Sun's atmosphere," among them. But its most common name is "zodiacal light." It is a faint glow of light found along the horizon and extending upwards in a pyramid shaped cone to almost overhead.

This cone of light is best seen near the time of the vernal equinox in the spring and the autumnal equinox in the fall, especially if they occur near the time of the new Moon. In the fall, the light is best seen in the morning before sunrise and in the spring in the evening after sunset.

That is because the ecliptic (the path the Sun follows during the year) is almost vertical to the horizon at those two times of the year. The zodiac follows the ecliptic, hence the name, zodiacal light.

This light comes from the reflection of sunlight off grains of dust orbiting the Sun in a disc in the galactic plane extending, by some accounts, out past the orbit of Mars. The dust comes from leftover bits from the formation of the planets, from asteroids grinding against each other and the odd comet or two passing through the inner solar system.

At this time of year, the best viewing will be in the two hours before sunrise and viewing to the east. It will appear as a faint cone of light reaching almost up to be even with the planet Venus. It will be about as bright as the Milky Way as seen in the summer.

Begin looking before the beginning of astronomical twilight. Astronomical twilight is about an hour and a half to two hours before actual sunrise, when the Sun is still 18 degrees below the horizon and no light is showing in the sky. This faint glowing is what has given it the name false dawn.

Sunrise today, Oct. 2, will be at about 6:44 a.m. MDT in this area, so the best time to begin looking is in the half-hour before 4:30 a.m.

But, come to think of it, I can see the light in the spring in the evening, so, going back to bed is an option too.

SKY WATCH: Last quarter Moon today. Mars and the Moon in conjunction today, the Moon in conjunction with the Beehive Star Cluster (M44) on October 5, and Saturn, Regulus and Venus on October 7, all early morning events. Now is the time to start your Mars watch. Tonight the Moon will be just to the east (left) of Mars. At present, Mars is located between Orion and Gemini and is visible high overhead about an hour before sunrise. As the days progress, Mars will be rising earlier each evening until Dec. 24, when it will be at opposition, or opposite the Sun in the sky, where it will rise at sunset and be visible all night.

Remember, if you get any e-mail about Mars being as big as the full Moon and brighter that anytime in the last 50,000 years, delete it. It is a hoax.

Next time: More astronomical blatherings.