IC 4756
Template:Short description Script error: No such module "Infobox".Template:Template other IC 4756 is a large bright open cluster in the constellation Serpens. Known as Graff's Cluster, it is bright enough to be seen with the naked eye and considered a fine cluster for binoculars or small telescopes.[1]
IC 4756 is also known as the Tweedledee Cluster (paired with NGC 6633 as Tweedledum), also as the Secret Garden Cluster.[2]
Metallicity of IC 4756 is similar to the Sun, at −0.02±0.01 dex.[3]
Stars
There are some noteworthy stars in the cluster. HD 172365[4] is a likely post-blue straggler in the IC 4756 that contains a large excess of lithium.[5] HD 172189, also in IC 4756, is an Algol variable eclipsing binary[6] with a 5.70 day period. The primary star in the system is also a Delta Scuti variable, undergoing multiple pulsation frequencies, which, combined with the eclipses, causes the system to vary by around a tenth of a magnitude.[7]
References
External links
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