Star Points for August, 2000; by Curtis Roelle Sign of the Teapot in Sagittarius Last month we turned our heavenly gaze southward to Scorpius, a Summer constellation close enough to the horizon that it appears to have curled its tail in order to avoid scraping it on the ground. We noted that the pattern of stars in the constellation bears some resemblance to a scorpion and found treasure in two fascinating galactic star clusters located near the stinger that were easy to see with simple binoculars. Following close on Scorpius' tail is another constellation of Summer low in the south. Sagittarius the archer is an unusual celestial specimen. Not because he is an archer, but because he is part man and part horse. His upper part is a human figure from the waist up. Below this is the body of a horse from the shoulders down. In other words Sagittarius has two arms and four legs. Various ancient cultures viewed Sagittarius as half man and half animal. In the earliest records his animal half was a goat, or more technically a Satyr. In ancient India the constellation was simply a bow and arrow. Somehow the two images met giving us the figure we now know as Sagittarius. Sagittarius has no bright 1st magnitude stars. The lack of bright stars and its location low on the horizon make Sagittarius difficult to pick out from light polluted areas. The primary feature of Sagittarius is a group of eight stars that form a teapot-shaped asterism. Readers with web access can check out several links to images associated with Sagittarius at the Star Points web site at http://www.erols.com/roelle/starpoints/. Scroll down to the bottom of the web page or search for "Star Point Illustrations." A small diagram of the teapot can be viewed by clicking the link labeled "Sagittarius 'teapot' Asterism". When observed under a dark sky, such as those you may encounter during a Summer vacation to the mountains or a seashore away from city lights the Milky Way can be seen splashing across Sagittarius like a glowing cloud. With some imagination it is easy to imagine the cloud as hot steam billowing out of the teapot's spout. The teapot is only the central part of the constellation. Sagittarius is ranked 15th in total area of the 88 constellations. The full extent of the constellation is visible at the web site by clicking the link labeled "Sagittarius Constellation Chart". The chart depicts Sagittarius as it would appear at 10 p.m. EDT in early August. As in last month's image of the constellation Scorpius the green line at the bottom of the chart represents the southern horizon and the red line near the top is the Ecliptic. In the upper right corner of the chart are two sets of squiggly lines. These represent the best two of Sagittarius' many nebulosities. The lower object is commonly known as the "Lagoon Nebula" and is designated Messier 8, or M8. It is visible in binoculars and is actually two objects in one: A star cluster and a nebulous cloud. A full color image is available on the web site by clicking the link labeled "Messier 8 (M8)". In images the nebula appears red because of the light of ionized hydrogen. To the human eye the nebula appears white or whitish- blue because the human eye cannot collect light like film or imaging systems can. The star cluster is visible left of center and is seen to be fully involved with the nebula. Across the center of the nebula you'll notice a dark lane. This is how the Lagoon Nebula got its name. Another prominent feature of the Lagoon Nebula is a bright knot of gas called the "hourglass". To view it at the web site click the link labeled "'Hourglass' in M8". A short distance above the Lagoon Nebula is the smaller and much fainter "Trifid Nebula", or M20. In photographs this nebula has two colors, blue and red. As mentioned before, the red is produced from the light of hydrogen. The blue is star light being reflected off the interstellar gas and dust. A color image of M20 can be viewed at the web site by clicking the link labeled "Messier 20 (M20)". There is also an image showing the relative positions of M8 and M20. The link is labeled "M8 and M20 together". There is a good example of another kind of object in Sagittarius. On the web site's constellation chart it is denoted as a fuzzy object to the upper left of the top of the teapot's lid. This object is the globular star cluster M22. A globular star cluster looks like a packed ball of thousands upon thousands of stars. See the photo on the web site at the link labeled "Messier 22 (M22)". M22 was discovered in 1665 and may have been the first globular cluster ever found. However, there is always the possibility that M22 or other globular star clusters may have been observed even earlier yet were simply assumed to be faint stars. Like M8, M22 is another easy object waiting for you and your binoculars or small telescope.