This week and next in Starwatch, I want to take you to the low southern skies for two of the best constellations of summer, Sagittarius and Scorpius.
These are two of my favorite constellations. Today I want to feature Sagittarius the Archer.
Unless you’re blind or you haven’t bothered to check out the starry summer skies, you’ve seen Jupiter in the low southeastern sky in the early evening. It’s by far the brightest star-like object in the night sky this summer.
You can use Jupiter this year to locate Sagittarius. Look just to the right and just a little below Jupiter for a pattern of seven bright stars that clearly draw out the pattern of a teapot. There are four stars on the left side that make up the handle, three stars on the right that make up the spout, and one between that marks the top of the teapot’s lid. But wait, didn’t I say that Sagittarius was supposed to be an archer?
Actually, it’s supposed to be a centaur shooting an arrow. According to Greek and Roman mythology, centaurs were half man, half horse and had a nasty reputation.
They had no tolerance for anyone who wasn’t their kind. In mythology, though, there was one well behaved centaur named Chiron, who was educated and had some manners. Unfortunately, he was accidentally killed by Hercules, whose constellation was featured last month in this column.
During a battle with an angry mob of centaurs, Hercules hit the gentle Chiron with a stray arrow. The gods of Mount Olympus felt sorry for Chiron and placed him in the sky as the constellation we see in southern skies of summer.
The only problem is that the constellation looks much more like a teapot, and that’s really how most stargazers see it. If you really want to make it into a half man-half horse, the best I can do for you is to suggest that the handle of the teapot is the elbow of Chiron pulled back to fire an arrow. The spout of the teapot is his bow and the star at the right point of the spout is the tip of the arrow.
This time of year is so great to get out to the countryside and stargaze away from city lights. It’s in the dark summer skies that you can clearly see the bright band of milky light stretching from the northern horizon to the southern horizon.
You’re looking sideways into the disk of stars that make up most of the stars in our galaxy. There are so many stars in the band and they’re so far away that you see their combined light all mashed together.
The constellation Sagittarius, on the southern end of the Milky Way band, is in the direction of the center of our galaxy, about 26,000 light-years away. (One light-year is almost six trillion miles.)
The downtown section of our home galaxy would appear a lot brighter in our sky, but there’s a lot of obscuring interstellar gas and dust in the way. Many astronomers believe that if it weren’t for all that gas and dust, the part of the sky around Sagittarius would be brighter than the full moon.
Nonetheless, that part of the Milky Way band around the teapot is fairly bright anyway, and loaded with a lot of fun stuff. Even with a small telescope or a pair of binoculars you’ll find many star clusters and nebulae.
In fact, with just the naked eye, if it’s dark enough where you’re stargazing, you’ll see what looks like a puff of celestial steam above the spout of the teapot. That “puff” is known astronomically as M8, the Lagoon Nebula, a bright emission nebula. It’s one of the larger and brighter star factories we can see in the sky, and you don’t need a really fancy telescope to get a good look at it.
This giant cloud of hydrogen, the raw material it takes to manufacture stars, is around 5,000 light-years away and roughly 100 light-years in diameter. Within this cloud many new stars are being born, some with solar systems and planets that could end up being like Earth.
Next week I’ll take you on a tour of Sagittarius’s next-door neighbor, Scorpius.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis. Visit his Web site, www.lynchandthestars.com
The Everett Astronomical Society welcomes new members and puts on public star parties. The Web site is members.tripod.com/everett_astronomy.
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