-- Back to Page 1Globular clusters are much richer aggregations, typically containing anywhere from ten thousand to a million densely packed suns. They’re tremendously impressive through telescopes big enough to show their individual stars, but through binoculars they usually look like small, fuzzy balls of light. One of the most impressive is the great
Hercules Cluster (Messier 13) in the Keystone asterism of Hercules, currently high in the western sky. In gazing upon this object, consider that the light you are viewing left the cluster some 24,000 years ago, when cavemen were still hunting mastodons. But that’s just the blink of an eye in a globular cluster’s lifetime. Many of them are more than 10 billion years old, among the oldest objects known in the universe.
At the opposite end of the spectrum, a stellar association is a very large and loose-knit formation of re-cently born suns that are all drifting through space together. One of the finest examples, the
Alpha Persei Assoication, is currently climbing the sky in the northeast. More than six Moon diameters in extent, it’s way too large for typical telescopic fields. But in binoculars, this radiant clan is truly an awesome sight!
Nebulas
Emission nebulas are stellar nurseries — clouds of gas and dust lit up by newborn stars within them. One of the most magnificent is the Lagoon Nebula, (Messier 8), which is visible low in the southwest right after dark in September. Its ghostly glow surrounds numerous glints of light from the embedded star cluster.
At the other extreme are planetary nebulas, which represent the death throes of aged suns ejecting their outer layers. Like the planets after which they are named, planetary nebulas tend to be tiny disks, appearing as simple points of light except when viewed through telescopes at high magnification. But two in the fall sky are big enough to show as extended objects through binoculars. The easier of these, by far, is the Dumbbell Nebula, (Messier 27). Larger but much fainter is the Helix, a dim glow that can only be seen far from artificial light pollution on a moonless night.
Galaxies
Newcomers to astronomy often assume that they will need a telescope to see galaxies. But many galaxies are visible as dim little gray glows through binoculars, and two of them appear quite impressive when viewed from pristine, dark locations in the Northern Hemisphere. (Observers south of the equator have it even better, because they can see the two Magellanic Clouds, the biggest and brightest galaxies of all — other than our own Milky Way.)
The brightest galaxy in the northern sky is the Andromeda Galaxy (Messier 31). Under moderately dark suburban skies, it’s visible as a faint smudge even to the unaided eye. In fact, at 2,500,000 light-years, it’s the most distant object that can be seen reasonably easily without optical aid. In all but the worst condi-tions, binoculars will disclose a bright, oval-shaped glow marking the central region of the galaxy. Sweeping across the Andromeda Galaxy on dark nights will reveal the faint outer sections, reaching many Moon widths from the center. Its two companion galaxies, Messier 32 and Messier 110 can also be glimpsed un-der good conditions.
The Triangulum Galaxy (Messier 33) is a much more challenging target. Although faintly visible to the unaided eye under pristine skies, its ghostly glow is easily overwhelmed by light pollution. Curiously, un-der marginal sky conditions, many people can see this galaxy more easily with small binoculars than through large telescopes.
The Milky Way
Saving the best binocular deep-sky wonder of all for last, let’s turn to our home galaxy — the magnifi-cent Milky Way! While sweeping it with telescopes is a thrilling experience, this awesome display is at its stunning best in binoculars. Late summer and early fall are the best times to view the Milky Way as it passes high overhead, flowing from horizon to horizon.
For observers at mid-northern latitudes, the most spectacular sections of our galaxy are the great star clouds in Sagittarius, Scutum and Cygnus. These appear to be milky areas of light to the unaided eye, but even the smallest optical aid reveals that they’re composed of innumerable stars. Slowly sweeping across any one of these amazing star clouds on a dark, moonless night with binoculars is an experience never to be forgotten!
Also noteworthy are the numerous dark areas, large and small, scattered throughout the Milky Way. Seemingly devoid of stars, these are actually opaque clouds of dust near the plane of our galaxy. One of the largest and most obvious is the
Cygnus Rift, which runs through the middle of that constellation’s North-ern Cross asterism. This inky river is particularly prominent because it’s right next to the Cygnus Star Cloud.
But there’s even more excitement to share about the Milky Way: the stunning illusion of depth percep-tion in its structure. While viewing the great billowy starclouds mentioned above, be alert for an amazing 3-D effect that can occur without warning. As the eye-brain combination makes the association that the fainter stars you’re seeing lie farther away than the brighter ones — that you’re actually looking at layer upon layer of stars — the Milky Way can suddenly jump right out of the sky as the three-dimensional starry pinwheel it actually is!
James Mullaney is the author of Celestial Harvest and Double & Multiple Stars. In 2005 he was elected a Fellow of England’s Royal Astronomical Society.-- Back to Page 1© 2006 Reprinted with permission from Sky Publishing Corp.
