NGC 6539
globular cluster
NGC 6539, or GCL 85, is a globular cluster of stars in the constellation Serpens. It was discovered by Danish astronomer Theodor Brorsen in 1856. This cluster is visible with a small amateur telescope, having an apparent visual magnitude of 9.6 and an angular size of 6.9″. It is located at a distance of 26.63 kly (8.165 kpc) from the Sun, and 10 kly (3.1 kpc) from the Galactic Center.
This cluster is located in the outer parts of the Galactic bulge. There is a large dark cloud complex located in the fore of this cluster, causing reddening from extinction. NGC 6539 has a core radius of 0.54′, a half-mass radius of 1.67′, and a tidal radius of 21.5′. Compared to other globular clusters, NGC 6539 is considered metal rich, indicating that it has a relatively higher abundance of elements more massive than helium. Thirteen variable stars have been detected within 7′ of the core, of which a dozen are long period variables. A millisecond pulsar was discovered in 1990.
Begin with the source’s own compact description: “NGC 6539” is globular cluster. The dossier treats that line as a proposition to test through globular and cluster, not as a finished interpretation.
Why this record matters
The phrase “globular cluster” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 4, 2026. The linked authority identifier is Q1146368. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1856 and 1990.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
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- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “NGC 6539”, its source revision and the description used here.
- Expand the search: follow NGC 6539 primary sources, NGC 6539 archive and globular research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “NGC 6539”?
- Which institution is responsible for the underlying evidence?
- Which cited source is closest to the event, object or claim?
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This entry incorporates text from “NGC 6539” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.