Thursday, July 08, 2004

Marvelous Milky Way

Marvelous Milky Way
by Dave Adalian

Cloudy nights are usually the bane of celestial sightseers but not always, not this time of year.
Recently a non-astronomer friend and I were stargazing from a dark site east of Exeter when he announced our session might be coming to an unplanned end.

“Look,” he said, pointing to the southeast, “some clouds are coming in.”

Instead of disagreeing, I pointed binoculars at the supposed storm front and let him have a look. He was quiet for a long time.

“What do you think?” I asked.

“That’s a lot of stars.”

My friend had discovered the Large Sagittarius Star Cloud, a hole in the dust that hides the bright edge-on view of our galaxy from Earth. What he was seeing that night were millions of stars in the Sagittarius Spiral Arm of the Milky Way.

As I mentioned last month, eight bright stars in the constellation Sagittarius form an asterism called the Teapot. It rides low in the southeast just after sunset, and the Moon can be used to find this stellar shape. On the night of July 27 the Moon sits to the right of the Teapot and the next night covers the Large Sagittarius Star Cloud.

It takes a moonless night far from town for finding the cloud that fooled my friend, but it’s worth the trip. This is especially true since the Large Sagittarius Star Cloud marks the gateway to one of the most beautiful stretches of night sky.

The cloud sits at one end of a white river of stars that cuts across the summer sky, Earth’s view of the Milky Way Galaxy. It’s easy to think of it as steam pouring from the Teapot’s spout.

The steam trails in wisps up and to the left of the Teapot. Besides the bright nebulas I listed last month, observers will also find the Small Sagittarius Star Cloud easily with the naked eye from a dark site. The smaller cloud is another hole through the dust.

Climbing along the trail of stars, are dark patches of dust and dozens of star clusters seen easily without optical aid. With binoculars, this trek is one of the sky’s best hunting grounds.

Before the trail ends at the other side of the sky, it meanders through another landmark of the summer sky, the Summer Triangle, a huge asterism formed in the east by the three bright stars Vega, Altair and Deneb.


This column originally appeared in the Visalia (Calif.) Times-Delta on July 8, 2004.