Звездное небо: как найти созвездие Стрельца и Млечный Путь в летнем небе

Downtown Milky Way This week in Starwatch, I want to take you to the low southern skies for one of the best constellations of summer, Sagittarius the Archer. Not only is Sagittarius easy to find, but it’s also in the direction of the center of our Milky Way galaxy, home of our Sun and at least 200 billion other stars with even more planets, some maybe just like our Earth. As soon as it’s dark enough over Butler, around 9:30 p.m., look in the low southern sky just above the horizon. You want to make sure your view is fairly unobscured with a low tree line. An open field is best. Look for a distinct pattern of eight fairly bright stars that clearly draw a teapot. Unless it’s really light-polluted where you are it should be very easy to see. There are four stars on the left-hand side that make up the handle, three stars on the right that make up the spout, and one in between that marks the top of the teapot’s lid. That celestial teapot is actually what astronomers call an asterism, a very easy-to-see pattern of stars that isn’t actually a constellation. In this case, the teapot asterism is the brightest part of the official constellation Sagittarius the Archer. According to Greek and Roman mythology, Sagittarius depicts a centaur shooting an arrow. In case you’ve never run into one, a centaur is a mythological creature with the head, arms and torso of a man, and the body and legs of a horse. With a slight overload of imagination, you may be able to see how the teapot could outline the upper body of the centaur shooting an arrow. The handle would outline the bent arm of the shooting centaur and the spout would draw out the bow and arrow. In mythology, centaurs had a nasty reputation. They were deceptive, despicable characters who drank too much and got into a lot of fights. They had no tolerance for anyone who wasn’t their kind. According to the legend, though, there was one well-behaved centaur named Chiron who was well educated and had some manners. He stayed out of the bars and preferred hunting for quail on his farm. Unfortunately, Chiron was accidentally killed by the great hero Hercules, whose constellation is also part of the summer sky. According to this classic epic, Hercules was taking on a battalion of rioting centaurs who were attacking him. Hercules fought them all to the death one by one and was riding off when he spotted another Centaur in the distance. This was Chiron, who just happened to be passing by on his way back from the library. Hercules, still emotionally heated up from his tumultuous struggle, figured Chiron was just another hostile centaur and hurled a spear at the gentle half-human-half-horsey, doing him in. Gentle Chiron was a favorite of the leading gods of Mt. Olympus, and when he got knocked off by Hercules, they felt sorry for him and placed his body in the sky in the form of the constellation we still see in the southern skies of summer. It’s really great this time of year if you can 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 are 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. (By the way, just 1 light-year is almost 6 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 still fairly bright and loaded with a lot of celestial treasures. Even with a small telescope or a pair of binoculars, you’ll find many, many star clusters and nebulae. In fact, if it’s dark enough where you’re stargazing, with just the naked eye you’ll see what looks like a puff of celestial steam above the spout of the teapot. That “puff” is known astronomically as Messier Object 8, or M8, the Lagoon Nebula. It’s a bright emission nebula where stars are being born. Even a small telescope gives a better view. 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 and planets are being born, lighting it up like a huge fluorescent light. It’s too bad that Sagittarius is so close to the horizon in our part of the northern hemisphere because our view of all these celestial goodies isn’t as clear as it could be. We’re forced to view them through a thicker layer of Earth’s atmosphere, and if there’s any extra humidity in the air, that makes it worse. Even with that it’s still rewarding to scan the sky for a celestial arrow shooting centaur. If you ever get a chance to see Sagittarius closer to the equator — in places like Central America or even in the southern hemisphere — I hear that the view of Sagittarius and vicinity is beyond awesome. That’s definitely on my bucket list! Mike Lynch is an amateur astronomer and professional 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 at adventurepublications.net. Contact him at [email protected].