The evening sky after twilight is free of the moon for the next week. If the monsoon permits, now is a good time to enjoy the summer Milky Way, which is nearly overhead at 10 p.m.

By far, one of the most awesome sights the sky has to offer is the summer Milky Way on a clear night far away from city lights. It can be enjoyed with the naked eye from a comfortable lawn chair, but if you have low-power binoculars, you will find innumerable star clusters and areas of nebulosity scattered from one end of the Milky Way to the other.

The Milky Way is our parent galaxy, sometimes simply called the Galaxy with a capital G. It is actually a flattened disk containing several hundred billion stars.

When we look in the sky toward the plane of the Milky Way's disk, we see thousands of stars seemingly piled on top of one another, thus giving the illusion of milk spilled across the sky. When we look away from the plane of the Milky Way's disk, we see many fewer stars, and there is no "milky" band.

The Milky Way is a very large spiral galaxy with several arms. We are located in one of its arms 25,000 light years from its center in the constellation Sagittarius.

The Milky Way wraps completely around the sky, and there are both a "summer Milky Way" and a "winter Milky Way." For Northern Hemisphere observers, the summer Milky Way is brighter and more spectacular than the winter Milky Way.

At the very center of the Milky Way is a large black hole gobbling up gas and stars - which sounds scary.

Fortunately, it is way too far away to bother us.

If you go

Friday's meeting of the Tucson Amateur Astronomy Association will start with a talk about how scientists discover the characteristics of individual stars.

Next, Craig Kulesa, an associate astronomer at Steward Observatory, will tell the story of building and operating a small autonomous observatory at the most remote place imaginable - the summit of the ice plateau in Antarctica. The location was needed for "far-infrared," or "terahertz" astronomy, which is a way of looking at the universe in a kind of light that's between radio waves and visible light.

The free event starts at 6:30 p.m. in Room N210 of the Steward Observatory, 933 N. Cherry Ave., on the University of Arizona campus.

Moon Watch

The moon is in a waning (growing smaller) crescent phase. The new moon is Tuesday.

Contact Tim Hunter at