Observer's Notebook for September, 2000

by John Rummel


Madison is squarely based in what geographers call "mid-northern latitudes." Located as we are about midway between the equator and the north pole, we are forever forbidden from seeing a significant portion of the southern sky. Due to the seasonal change in the Earth's orientation, we do get brief glimpses of some of these southern gems.

One such constellation, Sagittarius, rises far enough above the southern horizon late each summer and into early fall, and allows us to share in this wonderful and important constellation. Though its distinctive teapot-shape can be seen easily from light polluted suburban skies, you really have to get out into the countryside under dark skies to appreciate all the richness that Sagittarius has to offer.

Any evening during the latter part of September (so the bright moon won't interfere with the view), go to your favorite dark sky site and spot the teapot of Sagittarius riding above the southern horizon. If your skies are sufficiently dark, you'll be able to see the beginnings of the hazy milky way rising out of the top right of the teapot shape. Some constellation interpreters prefer to think of this as the steam rising from the pot - an image I can easily imagine as I gaze at this autumn beauty.

 

A photo of the Milky Way centered on the Scutum star cloud. Sagittarius is just off the bottom of the print. Visible on the right bottom are three bright nebula M16, M17, and M18. M16 is in Serpens, 17 and 18 are in Sagittarius. The hazy black smudge at the bottom center is the edge of the telescope tube - the camara is riding on top of the telescope - piggyback - for this shot.

Photo taken August 8, 1999 by John Rummel, MAS Yanna Research Station (south of Brooklyn, WI). Nikkormat SLR, 50mm lens piggyback on a C8 Deluxe. F/2.8, 12 minute exposure, ASA400 Fuji Superia. Image was lightly processed in Photoshop to brighten and enhance colors.

Actually, thinking of the milky way "beginning" in Sagittarius is not that far from the mark. The center of our galaxy lies in this direction. That spot where the steam rises out of the spout is pretty close. The galactic center is never visible directly because there is far too much dust and too many stars in the 20 to 30 thousand light years between us and the dense core. However, scientists using infrared and other wavelengths of light are able to penetrate much of this light-blocking material and plumb the depths of the galaxy. There they find more questions than answers - vast clouds of dust, thousands of bright, young stars, and possibly a monster black hole.

While you won't see a black hole, take your binoculars and scan the entire Sagittarius region from your dark sky sight. You'll notice rich star fields, many bright star clusters, and a few hazy fuzzy spots that are bright reflection nebulae. The brightest of these is known to astronomers as M8, or more popularly as the Lagoon Nebula. It is actually visible to the naked eye under really dark skies. It is located a couple of finger-widths to the right of the top of the teapot. Scan all around this area, and upwards along the milky way, through Serpens and Scutum. This area is rich in star clusters. One of my favorites is in Scutum, about an open-hand's width directly above Sagittarius. It's a beautiful cluster of stars known as M11, or popularly as the Wild Duck Cluster. Through a telescope the cluster resolves into hundreds of individual stars packed so tightly it's difficult to see the blackness of space behind it. Tucked right into the midst is a single orange star, a bit brighter than most, the "wild duck" I suppose.

A tour of the Sagittarius region with binoculars could occupy a patient star gazer for hours. If you get a chance, don't pass it up.

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