Sagittarius is a classic summertime constellation and this is the best time of year to see what the Greeks portrayed as Centaur aiming an arrow. It's what I call a low rider in the southern sky, rising in the southeast and setting in the southwest and never making it more than 25 to 30 degrees above the southern horizon. This time of summer Sagittarius starts out after evening twilight just above the direct southern horizon. You certainly won't crane your neck viewing Sagittarius. Allegedly you're supposed to envision a menacing centaur shooting an arrow at it neighboring constellation Scorpius the Scorpion. At least that's how the early Greeks saw it. Now if you're not quite up to speed on your mythological monsters, a centaur is creature that has the head of a man or woman, and the body of a horse.
Forget about all that! Sagittarius looks just like teapot! Anybody I've ever shown this constellation says the same thing. It's easy to see as most of the stars are nearly as bright as those in the Big Dipper. There's three stars on the right side that form the spout, four stars on the left side that outline the handle, and one star that marks the top of the teapot. It looks as if the teapot is pouring hot celestial tea on to the stinger tail of neighboring Scorpius to the west causing its tail to curl.
One of the noteworthy stars of Sagittarius is Nunki, positioned on the upper left hand corner of the teapot's handle, It's pronounced NUN-key and is one of the cuter star names. Most traditional star names are Arabic, Greek, or Latin but Nunki is a HYPERLINK "http://en.wikipedia.org/wiki/Babylonian" \o "Babylonian" Babylonian name. Even though it has a cute name it's one powerful star 230 light years away. It's over four million miles in diameter, more than five times the diameter of the sun and over seven times as massive and get this, Nunki kicks out more than 3000 times as more light than our home star.
Sagittarius is not only a fun little constellation that but it literally points to the downtown neighborhood of our Milky Way Galaxy. In fact the spout of the teapot points right at the central point of our home galaxy. Now if you're lucky enough to be viewing Sagittarius in the country away from the incessant light polluted city skies, you'll clearly see the band of light we call the Milky Way arching from the northeastern horizon to near the overhead and on down to Sagittarius in the south. Now every single star we see in our sky anytime of year is member of our Milky Way, made up of nearly a half a trillion stars, but the Milky Way band that we see is the combined light of billions and billions of stars that make up the central plane of our galaxy and the region around Sagittarius is in the direction of the hub of our disk shaped spiral galaxy.
You would think that part of the sky around Sagittarius would be really bright but dark interstellar clouds of gas and dust block our visible view of the Milky Way's center. It's been said that if we could see the center unobstructed, that part of the sky would be brighter than a full moon! What astronomers know about the center of our galaxy comes from radio and x-ray astronomy from Earth based observatories as well as orbital observatories like the Chandra X-Ray telescope. The nucleus of our home galaxy is a region of chaos that takes a gifted imagination to fathom. Stars are rammed together much more so than our part of the galaxy. Many Astronomers believe that stars close to the nucleus are separated by less than two trillion miles, and as they whirl around the galaxy's center at breakneck stellar speed, stars collisions are commonplace. What's causing the stellar chaos is a giant black hole at the exact center of the Milky Way that's more than a million times the sun's mass made up of the corpses of dead stars that have been swallowed in the galactic abyss.
Despite the dark clouds hiding most of downtown Milky Way, There's a lot of cool stuff to see in an around the Sagittarius teapot. If it's dark enough from where you're viewing, you might even see "a puff of steam" with your naked eye just about at the teapot's spout. That's the Lagoon Nebula, a massive cloud of hydrogen gas being lit up by stars within like a giant fluorescent lamp. The lagoon is over 4000 light years away, or if you prefer, 26,000 billion miles from your backyard. As far as that is, that's celestial chicken feed compared the center of our galaxy that's over 25,000 light years away. I would put that in miles but newspaper inks gets a little spendy.
With larger telescopes, there's a lot of other star clusters and nebulae to peruse in and around the arrow shooting centaur. There are amateur astronomy and celestial photography targets like the Eagle Nebula, the Trifid Nebula, the Omega nebula and many more. Also, At last count astronomers know of sixteen stars in Sagittarius that have planets circling them, more than planetary any other constellation.
The teapot is boiling over!
Diagram of Sagittarius...Click