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Astronomy ... and You, 2020
“Uncle Bob”

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Sagittarius ... and You

chart of Scorpius (right) and Sagittarius
courtesy of Stellarium via

Sagittarius …

In early September, just after sunset, the view at the southwest horizon contains the red star Antares, literally the enemy of Mars, and just to its right three white stars in a bent vertical line. The group represents the heart and the head of the Scorpion. The deadly hooked tail to the south will be hidden below the horizon at northern locales. At this time Sagittarius and its Teapot asterism will appear prominently, albeit low in the south. By month’s end, the Teapot will slide west and replace the Scorpion. This region in summer holds many treats for a small telescope, binoculars, or even the unaided eye.

First, the Teapot can hardly be missed. It is approximately 16 degrees wide and 10 degrees from base to lid. On the chart below, three more lines needed to be drawn to complete the base, the spout, and the handle. I can’t fathom what protocol prevented it. The remainder of Sagittarius, the Archer, is not all that photogenic. The character seems to have originated in the ancient Sumerian civilization living along the Euphrates river. He was an arrow-shooting god of war. The Greeks later enhanced the role making him an arrow-shooting centaur, half man half horse. By the way, he is aiming at the Scorpion.

M this and M that. You see above that the Teapot area is rich in M objects. These are entities in a catalog compiled by French astronomer Charles Messier in the 18th century. He was a comet hunter, a hobby alive and well even today, especially since 1994 when pieces of one, the “string of pearls,” blasted and blackened Jupiter’s atmosphere. Messier was actually annoyed by these other objects that gave him a rush when scanning the skies. Let others be warned: these are not comets. Merci, Monsieur Messier. De rien, mon plaisir,

Not comets, however they are jaw-dropping, eye-opening objects that give us windows into aspects of our universe that were unknown until recently. Two of the more well known are pictured below. M20, the Trifid Nebula looks more like sci-fi than sci. As a matter of fact Trifids were a weird race of ETs terrorizing Earth in a low-budget 50s movie. Long exposures and filtering reveal M20’s many colors. M8 [right] is larger and more varied – it’s called the Lagoon. On a dark night these are visible without instruments.

[left] Trifid Nebula M20, Dylan O'Donnell,
under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
[right] Lagoon Nebula M8

In addition to the bright nebulae and star clusters in the region, Sagittarius and its column of rising steam, sometimes referred to as the Milky Way, also are home to the dark nebulae. These are areas that appear devoid of all objects, and until recently they fooled the best astronomers. “A dark nebula or absorption nebula is a type of interstellar cloud that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebulae.” -wikipedia. Only radio or infrared astronomy can “see” what’s beyond these clouds. Below are pictured the dark lanes in and around the Lagoon Nebula.

The Lagoon’s dark lanes

Author: ESO/IDA/Danish 1.5 m/ R. Gendler, 19 April 2010
U.G. Jørgensen, K. Harpsøe under Creative Commons Attribution 4.0 International License

… and You.

1. Give yourself a tour of the Messier objects, especially ones near the Teapot.

Click on one to get an enlarged image, then use the back button to return to the set.

2. Modern cameras, filters, and processing give us spectacularly colorful images of Messier and other objects – and those look nothing like what we see from the back yard. Take advantage of these comfortable September nights and make a few pencil sketches of what youactually see with or without your binoculars. Sketch the Teapot and the outlne of its portion of the Milky Way.

3. Share [safely over the web] Uncle Bob’s astro articles and the many links therein with a friend – especially a young person.

Next Month: Cygnus, the Swan

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