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Binocular Universe: So Long, and Thanks for the Fish
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First its claws rise above our southeastern horizon. Then comes its brilliant red heart. Finally the hook-shaped tail makes an appearance. Scorpius, the Scorpion, is one of the most recognizable constellations in the entire sky. Within its borders is a bountiful selection of beautiful deep-sky objects strewn across some of the finest heavenly star fields. One of my favorite ways to spend a warm, clear summer evening is to simply sit back and casually scan the Scorpion's crooked body from head to toe. Along the way are many elegant asterisms, clusters and nebulae which provide hours of fascinating sky watching.
Above: Summer star map from Star
Watch by Phil Harrington.
Above: Finder chart for this month's Binocular Universe.
Chart adapted from Touring
the Universe Through Binoculars Atlas (TUBA) by Phil Harrington and
Brilliant Antares is dazzling in our southern summer sky, like a lighthouse beacon peering out from among an ocean of fainter stars. Even though it is more than 600 light years away, Antares is one of the sky’s brightest stars because of its immense size. We were discussing the B-V Index system for rating a star’s color in last month’s column. Recall that a positive number indicates an orange or red star, while a negative value is toward the blue end of things. Antares has an index value of +1.8. A positive value is not unexpected for a red supergiant nearing the end of its life. The hydrogen-to-helium fusion process powering Antares since birth has run its course, causing the star to swell to enormous proportions. Antares is so large that it were placed where our Sun is, its outer edge would extend nearly to the orbit of its namesake, Mars. (I say namesake because Ant-Ares literally translates as "rival of Mars," owing to the star's similar appearance to the Red Planet as well as its proximity to the ecliptic. You can judge for yourself this month, since Mars is truly Antares’ rival this month as it lies just west across the border in Libra).
Antares is always a fun object to enjoy through binoculars. Its deep reddish color, rivaling that of Betelgeuse in winter's Orion, is readily apparent. Often, however, Antares appears to flash through many other colors because of interference from our atmosphere. The fact that Antares rides so low in most of our skies only accentuates this sparkling effect.
With Antares immersed in the glow of the Milky Way, it makes a wonderful jumping off point for many hidden treasures that lie in wait. Let's begin with the globular cluster M4. You don't need to move a muscle to see it once you're staring at Antares; just look half a degree to its west. Look for a dim, round glow that resembles a distant ball of cotton.
At 7,200 light years away, M4 is relatively close to us as globular clusters go. This makes it appear bigger than most, and easy to identify through even 6x binoculars. But because M4 is quite loosely structure, its lack of a condensed center can confound observers who must battle light pollution.
Scorpius is also home to a second Messier globular cluster that proves more challenging through binoculars. M80's small, dim disk rests halfway between Antares and Beta (ß) Scorpii. Although its star-like core makes it more typical of the breed, M80 is tiny compared to M4, so identifying it from among all the surrounding stars can be a challenge.
Two degrees southeast of M80 and 3° northwest of Antares, we find Rho (ρ) Ophiuchi, a striking triple star for binoculars. Here, we find a 5th-magnitude primary star set in a tight triangle with 6th and 8th magnitude companions. All three are spectral class B. While the same class, they are not the same size. The primary is a subgiant, while the others are dwarf stars. All appear the slightest bit blue through binoculars. Two other members of the system remain unseen in binoculars, but raise Rho Ophiuchi to a quintuple star.
The family Rho is also surrounded by very colorful but extremely faint clouds of reflection and dark nebulosity. The bright clouds are collectively catalogued as IC 4604, while the dark nebula is listed as Barnard 42. Although they record vividly in photographs, I do not know of any visual sightings of either. We can certainly see their influence, however. The opaque dust dims Rho by two magnitudes. Lousy pollution!
Now, place Antares at the western edge of the field and look on the opposite side for a close-set pair of 5th-magnitude stars, lying across the invisible border in Ophiuchus. The globular cluster M19 lies just a degree to their south. Looking a little larger and a little brighter than M80, M19 should reveal itself as a slightly fuzzy "star" through 7x binoculars. While viewing M19 through his 10x50 binoculars, amateur Jim Elliott from Lee County, NC, once pointed out that there is an unusual arc of three optical double stars curving around M19 to the northeast. I call this curious assembly of stars, which include 24, 26 and 36 Ophiuchi, the Dish O' Doubles, since they remind me of a satellite dish, with M19 at the focus.
On paper, M62 sounds as though it should be a twin of M19. But when you look for it, about half a field to M19’s south, it proves more difficult to see. Observing from the Naylor Observatory outside of Harrisburg, PA, several summers ago, CN’er Dave Mitsky described M62 as "a small, featureless fuzzy through my 8x42 binoculars. However, my 15x70 binoculars revealed a brighter, stellar core."
One of my favorite summertime asterisms lies just 1.5° southwest of M62. If you're a gardener, you'll recognize it right away as a celestial garden trowel. Give John Davis from Amherst, MA, credit for digging up this one. Davis draws the trowel from three 7th-magnitude stars set in a southward-pointing triangle and a trail of three additional 6th- and 7th-magnitude stars meandering off to the north. While most of the Trowel's stars are white, two or three shine with a subtle golden glint.
Looking for more to look at this month? The list below will keep you busy for many a night!
Let me close with some good news, some bad news, and then some more good news. First, the good news. As subscribers to Astronomy magazine may have already discovered, the July issue contains the first installment of my resurrected Binocular Universe monthly column. I say resurrected because the column ran there every month from June 2005 until May 2009. Beginning the following month, Binocular Universe migrated to CN, which brings us to this day.
So, what’s the bad news? Rather than try to produce two quality features every month, I have told the Cloudynights team that this will be my final BU column here on CN. It’s been a wonderful run. Along the way, I have communicated with many fellow binocularists who share my passion for the two-eyed sky. Thank you all so much for your support.
And the second good news? I am not disappearing from Cloudynights! Au contraire, I will be right back here next month, starting a new monthly feature based on the concept of my book Cosmic Challenge. Each month, we will search for objects that are purposely difficult to find. After all, half the thrill is in the hunt, isn’t it? Some columns will feature challenging targets for large telescopes, other months will hunt for prey suitable for smaller instruments, and still others will be geared for binoculars or the eye alone. I hope you will join me here to test your observational skills.
That's it. So, until we meet back here again, remember that two eyes are better than one.
About the Author:
Phil Harrington is a contributing editor to Astronomy magazine and author of 9 books on astronomy, including Touring the Universe Through Binoculars. Visit his web site at www.philharrington.net to learn more.
Phil Harrington's Binocular Universe is copyright 2016 by Philip S. Harrington. All rights reserved. No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder.
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