Object of the Week June 28, 2015 - NGC 6712 The Weird Globular
NGC 6712
Type: Globular Cluster
Constellation: Scutum
RA: 18h 53m 4.9s
Dec: -08° 42’ 20”
Size: 9.8’
Mag: 8.1
IC 1295 PK025-4.2
Type: Planetary Nebula
Constellation: Scutum
RA: 18h 54m 37s
Dec: -08° 49’ 39”
Size: 1.7’
Mag: 12.7
Mag of Central Star: 15.0
NGC 6712 was discovered by William Herschel on June 16th, 1784. Designated as H I-47 Herschel described it as “Bright, very large, irregularly faint, easily resolvable stars visible.” The later NGC description is similar, “Globular cluster, pretty bright, very large, irregular, very gradually, then a little brighter in the middle, well resolved, clearly consisting of stars, 15 stars.”
n6712.jpg
NGC 6712 is a relatively small (64 light-years across) and sparse (~1 million stars) globular cluster, which lies 22,500 light years away from us. The easiest way to find this globular is to first locate M26, a well-known compact rich open cluster; from there 6712 is a short 2-degree hop to the northeast.
A study by the European Southern Observatory concludes that NGC 6712 is only a pale remnant of a once much more massive cluster. It notes that none of NGC 6712’s stars are less massive than our Sun, making it totally unlike any globular cluster. Most likely, NGC 6712 is unique only because no other globular cluster comes as close to the Milky Way’s center as does NGC 6712; it penetrates very deeply into the galactic bulge, venturing to within 1,000 light-years of the galactic center. The tidal force of the galaxy not only strips low-mass stars from the cluster but also stretches out the cluster like a comet’s tail.
The ESO study labels NGC 6712 a peculiar globular cluster – and rightfully so based on the study’s findings. The recently published Interstellarum Deep Sky Atlas labels 6712 as The Weird Globular. A Google search failed to turn up any background on the derivation of this name. Perhaps a reader of this OOTW will be able to provide more info.
NGC6712_jt.jpg
Copyright by Jim Thommes
Under a good dark sky, the globular should be readily detectable as a faint glow in 10x50 binoculars. Moving to a 6-inch scope some stellar resolution is possible, with the brightest stars in the globular cluster being at magnitude 13.3. NGC 6712 becomes resolvable with a 15-inch scope at 172x. Though it is brighter towards the core, the core itself is granular in appearance and surprisingly seems to be less dense then some of the outer regions. It gives the appearance that the core is somewhat off center. The globular is not symmetrical, with one side appearing flattened to an obtuse inverted-vee.
While observing NGC 6712 you can’t avoid coming across IC 1295, a planetary nebula that is only 25’ to the southeast of 6712. Though not the subject of this OOTW this planetary nebula is well worthy of a visit. It responds strongly to both OIII and UHC filters. With either of these filters it appears as bright, if not brighter, than its neighboring globular cluster. Together in a rich field these two objects provide a pleasing, yet interesting contrast.
ic1295_cqk.jpg
Copyright C.Q.Kimball
NGC-6712-IC-1295_mj.jpg
Copyright ManualJ
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