Mike Lynch’s Skywatch: The tipping teapot is steaming

6September 2020

After the evening twilight has been chased away, look in the low south-southwest sky any evening in September. Without too much effort, even in moderately light-polluted areas, you should be able to see a constellation that resembles a teapot hanging diagonally by its handle. A distinct triangle of three bright stars make up the spout on the lower right side, and a trapezoid of four stars on the upper left make up the handle. In between and above the handle and the pot is a single star that marks the top of the teapot.

This celestial teapot is formally known as Sagittarius the Archer. By the way, I love the name of the uppermost left star in the handle. It’s Nunki, pronounced Nun-Key. Nunki is just over 225 light years, or 1,300 trillion miles, away. If you were to put it side by side with our sun, it would be over 3,000 times brighter, with a diameter four times larger than that of our home star.

According to Greek lore, the constellation Sagittarius is a centaur flinging an arrow to the west. With a little imagination, you can see a figure of a person shooting an arrow. The spout stars outline the bow, with the tip of the arrow at the tip of the spout. The four stars of the handle would be the cocked elbow of the shooter. The top of the teapot would be his head. Imagining a centaur flinging an arrow is a different matter, because a centaur is half person-half horse. The upper half of their bodies are human, with a chest, arms, and a head. Their lower half, though, are horse-like, complete with four legs and a tail!

Centaurs in Greek mythology were not the nicest creatures. They were mainly vagabonds and barbarians that were not all that bright for the most part. Centaurs had a hard time getting along with people and vice-versa. There were some exceptions, and one of them was the unlikely friendship between the centaur Chiron and the Greek hero Hercules. Unlike most centaurs, Chiron was highly intelligent, and he and Hercules had a lot of good times together. The other centaurs took exception to this and wanted to eliminate Hercules. Chiron was unaware of this plot, so he was caught off-guard when a herd of centaurs made a nighttime attack on Hercules’ house. Being greatly outnumbered, Chiron was helpless to stop them. However, the mighty Hercules was able to defend his turf by heaving countless arrows at the centaurs as rapidly as machine gun fire. Unfortunately, one of his arrows killed his friend Chiron. After Hercules fended off the attack he made the tragic discovery. Hercules was grief-stricken and begged Zeus, the king of the gods, to transform Chiron into the constellation we see in the summer skies, shooting an arrow at the neighboring constellation Scorpius the scorpion.

Despite that story, Sagittarius looks much more like a teapot, and this year the bright planets Jupiter and Saturn are just to the upper left of the teapot’s handle. Later this autumn, Jupiter and Saturn will be drawing closer and closer to each other in the night sky. On Dec. 21, they’ll be practically “touching” each other. It will be the closest conjunction between the two largest planets in our solar system since the 1600s! Actually, the planets are nowhere each other, they’re just nearly in the exact same line of sight.

If you’re lucky enough to be stargazing in the glorious dark skies of the countryside, you’ll easily see a ribbon of ghostly light arching overhead. It stretches all the way from roughly the northern horizon to the southern horizon. This is the famous Milky Way band, the thickest part of our home galaxy. You can’t help but notice that the Milky Way band runs right into the right side of Sagittarius. That’s not steam you’re seeing coming from the spout of the teapot, but rather the central region of our Milky Way Galaxy. That “steam cloud” would appear a lot brighter if it weren’t for a whole lot of obscuring interstellar gas and dust.

Trifid Nebula (Photo by Mike Lynch)

The Milky Way band around Sagittarius is loaded with a lot of fun stuff. It’s a very busy part of the sky, and even with a small telescope or a pair of binoculars you’ll find many, many star clusters and nebulae. Some of the better ones include the Eagle Nebula (M16), the Swan Nebula (M17), and the Trifid Nebula (M20). The M numbers are Messier catalog numbers. The Messier catalog is made up of the brighter clusters, nebula, and galaxies available in the night sky. A great app to help you find these objects these is Sky Guide, and a great website is Stellarium-web at stellarium-web.org.

Lagoon Nebula (Photo by Mike Lynch)

Just above the spout of the teapot there’s a more intense pocket of stars. That’s actually the Lagoon Nebula, a bright emission nebula astronomically known as M8. It’s one of the larger and brighter star factories we can see in the sky, and you don’t need all that much of a telescope to really check it out. Visually it has a greenish glow. That’s how it got its name.

The Lagoon Nebula is a huge cloud of hydrogen, the raw material needed to mass manufacture stars gravitationally. It’s over 5,000 light-years away and roughly 100 light-years in diameter. Just one light-year equals close to 6 trillion miles. New young stars produce so much ultraviolet radiation that they light up the Lagoon like a fluorescent light.

Enjoy the Lagoon Nebula and all of the celestial treasures around Sagittarius. That little teapot is boiling over!

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is also the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net.   Mike is also available for private star parties. You can contact him at mikewlynch@comcast.net.

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