See Saturn, Find Milky Way Treasure

Saturn dominates the scene at center in this photo taken on June 20. To its right you can see the Galactic Dark Horse standing on its tail with legs sticking out to the right. Several bright Milky Way star clouds are also visible including the Small Sagittarius Star Cloud (left) and the Large Sagittarius Star Cloud below and left of Saturn. Antares peeps between the branches at middle right. Can you find the firefly? Credit: Bob King

Saturn is the brightest object in the southern sky at nightfall at the moment. It forms a very wide pair with Antares,  a bright, red-hued star one magnitude fainter than Saturn. At 11 p.m. local daylight time, Antares stands due south with Saturn a fist and a half (15°) to its east or left.

The bright dot is Saturn and it shines on the back of the Galactic Dark Horse, a collection of dark nebulae in the constellation Ophiuchus that resembles a prancing horse. I rotated the photo 90° to the right, so the horse appears upright.  Credit: Bob King

The bright planets and the moon can be very useful in finding fainter things. Inside a 10° wide circle centered on Saturn a rich assortment of deep sky objects visible to both the naked eye and binoculars beckons. They include a prancing horse of interconnected dark nebulae, a bright open cluster, several nebulae and a stunning star cloud 10,000 light years from Earth. Some regions of the sky are sparse, but not Saturn’s present location in the heart of the Milky Way. Like a trip to the downtown of a big city, no matter where you turn, there’s something that catches your eye here.

Before the bright moon returns and spoils the fun, head out to the countryside and dark skies with a pair of binoculars for a look. Don’t forget the bug spray! A telescope will give even better views but isn’t necessary. You can see everything I’m about to describe with binoculars. Wide-field types are the best, the better to take in the grandeur of the scene.

In this telephoto view, Saturn is the bright dot at right. Puffy star clouds of the Milky Way dominate, while smaller clumps of star and gas — nebulae — dot the field of view. See the labeled photo below to identify some of the brightest binocular objects. From left to right, the photo covers about 20° or two fists of sky. Credit: Bob King

Serendipitously, Saturn is seated on the back of the Galactic Dark Horse, a large collection of dark nebulae some 10° long by 7° wide that bears a striking resemblance to a prancing horse. Dark nebulae are vast clouds of cold dust and gas spewed by generations of aged stars and supernovae. They’re dark because no star or stars are nearby to illuminate them; instead we see them silhouetted against the more distant stars of the Milky Way, which they block from view.

To see through and into dark nebulae, like Barnard 68, shown here, astronomers photograph them in infrared light. Notice how this dark cloud appear smaller and more transparent the farther into the infrared part of the spectrum we see it. The top left photo is closest to visible light; the bottom left is deepest into the infrared. Credit: ESO/SOFI

Dark nebulae may appear like a whole lot of empty, but they’re anything but. Mostly invisible to the eye, denser pockets of material within their inky billows are collapsing under the force of gravity to birth new stars and star clusters. The Orion Nebula used to be wholly dark, but stars born there as recently as 30,000 years ago now cast their light into its dark recesses.

All the objects labeled are visible in 35mm or larger binoculars in countryside skies. Some, like the Lagoon, Eagle and Swan Nebulas and M23 are even visible from the outer suburbs of medium-sized cities. The star clouds look like brighter tufts or clouds within the band of Milky Way. In the star cloud names, “Sgr” is short for Sagittarius. Credit: Bob King

The Dark Horse is faintly visible as a soft-edged dark space around Saturn. Probably the easiest parts to see are the lower leg and rump. Use averted vision, the technique of playing your gaze around an object rather than staring squarely at it. With a dark sky and patience, I was able to see almost the entire horse without optical aid. Binoculars will make a big difference, especially if they’re 40mm (ie. 8×40, 7×50, 10×50) or larger. Avoid high-magnification! The horse is so big, it’s best with a magnification of just 7-10x.

The Lagoon Nebula or M8 in Sagittarius is a star-forming region in our own galaxy illuminated by a young star cluster within the nebula. The Lagoon is about 5,000 light years from Earth about 100 light years across. It’s faintly visible with the naked eye and very easy to spot in binoculars. Credit: Hunter Wilson

The best time to view these Milky Way gems is in late June from 11 p.m. to 1 a.m.; mid-July from 10 p.m. to 1 a.m. and mid-August from 10-11 p.m. Start at Saturn, and after you’ve explored the Dark Horse, slide east about 1.5 fields of view (the circle view you see when holding the binoculars to your eyes) to the east (left) to find the bright, sparkly open star cluster M23. Drop down a field to the Lagoon Nebula, an obvious knot of haze with several embedded stars, and the much smaller Trifid, a short distance above it. Just east of the Trifid, look for the small star cluster, M21.

This photo taken with the Hubble Space Telescope shows the famed Pillars of Creation inside the Eagle Nebula. They’re tendrils of dark cosmic dust seared and shaped by the intense radiation from young stars within the cluster. You’ll need at least an 8-inch telescope to see a hint of them but the larger nebula-cluster combo is visible in binoculars. Credit: NASA/ESA/Hubble Heritage Team

If you continue east from the nebulae, you’ll run into the magnificent Small Sagittarius Star Cloud. Measuring about 1½° across, its real diameter is 600 light-years, and it resides within the Sagittarius spiral arm an incredible 10,000 light-years from Earth. Binoculars and telescopes break it up into spangles of faint stars blotted here and there by several small dark nebulae. Further east and north, you’ll spy the loose open cluster, M25 and the fuzzy blobs of the Swan and Eagle Nebulas. Their names come from their shapes, which are best viewed in a modest telescope.

With Saturn’s help we can explore the riches of the southern Milky Way this summer, visiting places thousands of light years from home. Happy trails!