There's no denying it now. The sun, now past its standing still point (Solstice) means that the Earth is now tilting back toward its winter orientation. Thankfully, it's a very slow journey! Daylight having reached its maximum lengths, will also begin to shorten by a few minutes each day. For the Lawnchair that means that the evenings will start a wee bit earlier, last a little longer and provide more time to enjoy those favorite summer constellations along the southern horizon. It is perhaps the most anticipated season for Lawnchairs everywhere. The warm comfortable nights of July, combined with the easily viewed sights within Sagittarius and Scorpius, are what many enthusiasts wait for all year long. And these DSO packed constellations await your perusal.
I'll never get over the sheer numbers of stars in this area. Within a wide angle lens, it's like looking at a giant star cluster. I guess, if you think about it, that's sort of what the Milky way really is. Under exceptionally dark and moonless skies it is simply magnificent. Rising up from the tree line, the Summer Milky Way displays both bright and dark lanes of proto stellar materials. Small and large star clusters and the awe inspiring nebulous patches are predominant in and around both of these constellations. Seeing them in person is one of those activities that is sure to compel a lifelong relationship and appreciation of a comfortable Lawnchair.
There are more than twenty different Messier objects in and around these grand southern horizon situated constellations, fifteen in Sagittarius alone. It has the biggest number of Messiers of any constellation. Just a simple binocular scan through the area will provide a substantial hint of the massive star clouds of the Sagittarius Milky-Way, while a small to medium-sized telescope will reveal an even more impressive view. For an even more revealing look, go online (http://hubblesite.org/) and see what the Hubble Telescope has photographed in the last two decades. Some of the most enigmatic Hubble photographs come from within this small section of sky.
Mere eyes alone cannot actually detect the tens of thousands of stars that fill this area of sky, most just below the naked eye visibility limit. Only binoculars and telescopes can provide a window into this hidden phenomena. A simple sweep up from the horizon with any type of optical aide will reveal the millions of dim stars congealed to produce that famous "milky" glow we see with just out eyes.
Besides the ability to magnify, the primary task of binoculars and telescopes is to gather light. The larger the instrument's aperture, the more light it can draw. Hence, when pointed toward the night sky, a telescope sees into this magnificent realm that our eyes alone cannot. However, we can see about 3000 stars just by looking up from a truly dark sky site without any extra help.
The Teapot asterism of Sagittarius is a very easy naked eye constellation to recognize as it climbs up above the southern horizon. But the Teapot is not all there is to the constellation. Just as the Big Dipper is not all there is to Ursa Major, the Teapot is only the top right corner of a larger constellation residing just below the horizon from the vantage point of Lawnchairs in the northern hemisphere. But that's ok, since the Teapot section is where most of the action is.
Once your eyes become dark adapted you'll be amazed at how rich this portion of the sky really is. Some of the most famous and photographed sights reside here. The Trifid Nebula, M-20, and the Lagoon Nebula, M 8, are a few prodigious examples. Robert Burnham Jr. described M-8 as "one of the finest of the diffuse nebulae", and, "plainly visible to the naked eye as a comet like patch just off the mainstream of the Sagittarius Milky Way". Once you've found the Teapot, M 8 is seemingly floating like a small puff of steam just above the spout section. This object is more than just a cloud of gas though.
This mongrel of a deep sky-object is in itself worth a small library's worth of descriptive notes. Combined of elements such as star clusters, coal black lanes of dust and more traditional nebulous attributes, M 8 has always been an object of intense study and debate. The Lagoon Nebula gets its name from the dark rift that intersects its central region. More like a channel than a lagoon, this superimposed blotch changes from grey to impenetrable black. Additional dark globules can be detected throughout the area. Some astronomers believe they might perhaps be the precursors to star formation as seen during earliest stages. And then to add even more to an already full dance card, a loose cluster of bright stars float among all this nebulosity. Throw in more than just a smattering of dim stars to pepper the field and you've got a good idea of what to expect from M-8.
There are also other visual treats as you move about the Teapot. For example, the further south you are, the better your chances are for picking up M-75. It is a fine, though small globular cluster on the border with Capricorn, as is M 55, also a smallish, though rewarding globular at the lower sections of Sagittarius.
Besides the many bright clusters and diffuse nebula that Messier located, the area is filled with dozens of objects that are listed in the NGC (New General Catalog) that professional astronomers use today. Unfortunately, most of these are beyond the reach of backyards instruments. Many were found with the largest earth bound telescopes and/or long exposure photographs.
As you gaze through the thick star fields, clusters and nebulae of Sagittarius, an even more interesting tidbit about it is that it marks the direction to which the center of our galaxy is located. Today we know that the center is home to a massive black hole. This is the engine at the core of the Milky way spiral. By mid July Sagittarius gets as high above the horizon as it ever will. So this is the best opportunity to grab a peak at what is a privileged view into the center of our galaxy.
However, you should be aware that anytime you look at objects close to the horizon, the turbulence caused by varying temperature gradients can make images, especially those magnified in a telescope, distorted. Unlike looking at objects directly above or nearly so, you'll be looking through dozens, if not hundreds of miles of atmosphere. During the summer months, as the night cools, it doesn't do so uniformly. Therefore as you look toward the horizons, you must "see through" these often multi layered temperature gradients. It's quite similar to looking down a long highway on a hot summer day where, in the distance, you'll notice those mirage like distortions along the pavement.
The best location to begin an observation of this nature will be where you will have an unobstructed view to the south. Also, you'll want to be somewhere away from a southern horizon that is north of a large city. The light pollution will only obstruct a chance to observe these objects that are best seen from and in a truly dark sky.
Besides the cup o' tea in the realm of Sagittarius, where summer jewels abound, its next door neighbor, Scorpius, is also home to incredible sights. From the Sagittarius Teapot, if you scan toward the west (right) you should easily be able to make out the scorpion shaped constellation. If you look at where the imaginary coffee or tea would pour out from the Sagittarius spout, this is where the tail of the Scorpion sits right on the horizon. This area is often washed out from our local view because of the amount of atmosphere and turbulence so close to the horizon. But looking right across the horizon you will come to, what to me, looks more like an archer's bow and arrow. This is the head of the constellation Scorpius.
The brightest star here, the middle star of the archer's arrow is the very well known, ruby red star, Antares. The ancient Chinese called it the "Fire Star", while the Greeks referred to it as the "Rival of Mars". Both the French and Romans called it "Le Coeur du Scorpion", the Heart of the Scorpion. Unmistakably red, you'll be impressed when you train even just binoculars on this star. The only other like it is the red giant Betelgeuse in winter's Orion. These two candidates for "The Big One", a super nova, currently pulsate erratically though, slowly and, are also both energetic radio sources. Though, because it lies some five hundred light years away, if Antares were to go boom today, we'd wouldn't know about it for another five hundred years. Or, it may have already blown up and turned into a black hole and we'll find out soon, tomorrow perhaps. Isn't this a great science?
Now just a little hop away is where you can find one the largest globular clusters of the summer. Just point at Antares and shift over toward the west, (right) less than a degree and a half, and you'll see M-4. It is one of those jewels that you'll want to come back to see every summer. Also near Antares is a smaller cluster that should be apparent in a wide angle view that encompasses both M 4 and the red giant. M 80 is a wonderful globular in a large telescope. A "fuzzy", at best in a smaller instrument, with the application of a close up lens, you may still get a hint of its numerous constituents.
Elsewhere in Scorpius, as you'll learn from a sweep of the area, are fantastic star clouds and groups of clusters. M 6 and M 7 to name a few, are both easily seen in binoculars alone and, are that much more impressive in small to medium telescopes.
The southern horizon, in general, is filled with all sorts of "fuzzies and sparkles," as a recent acquaintance put it. And I can't disagree. Take a look for yourself and count up how many times you hear yourself gasping Oooo! or Wow! All you'll need is a good dark sky and a clear view to the south. And then, along with a comfy Lawnchair, some bug spray and your favorite refreshments, it can only lead to a great experience. I hardly recommend taking advantage of this time of year and sharing the adventure. I guarantee there'll be a steady line of observers at the eyepiece. There are also no rules that say you can't make a party out of it. The Lawnchair would never object to sharing the Milky way with friends and family, especially if some of them are charged with catering the gathering, manning the BBQ grill and, of course, acting as event bartender!
The Lawnchair Astronomer
Gerry Descoteaux is the author of “The Lawnchair Astronomer,” a Dell Trades paperback. He has been writing about astronomy for more than 25 years. He also played an integral role in the development of America Online’s pioneering distance education program known as AOL’s Online Campus and served as Professor of Astronomy there for 10 years. He can be reached at TheStarMan@thelawnchairastronomer.com.
Notes From the Lawnchair