Gizmodo.com's Astronomers Spot Unprecedented Flashes From Our Galaxy's Black Hole mentions Sgr A*'s companion gas cloud G2 and that Wikipedia article uses the term perinigricon, but that mentions peribothron as a synonym.

So which term for an object's orbit's closest approach to a black hole is most frequently used; perinigricon or peribothron? And what are the origins of these competing terms?

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    $\begingroup$ There's probably a new answer to be posted for How do apsides of celestial bodies get their names? as well. $\endgroup$
    – uhoh
    Aug 13, 2019 at 5:40
  • $\begingroup$ companion question: How did they estimate the mass of Sgr A*'s companion G2 without knowing what it was? $\endgroup$
    – uhoh
    Aug 13, 2019 at 6:01
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    $\begingroup$ You mean it's not periholion? $\endgroup$
    – Mike G
    Aug 13, 2019 at 11:22
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    $\begingroup$ @MikeG If I ever switch field to black holes, I will use that term and acknowledge you in a footnote :D $\endgroup$
    – pela
    Aug 13, 2019 at 11:48
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    $\begingroup$ As far as I can tell, the usual term is "pericentre" (or "pericenter" if your local variant of English didn't pick up quite as much French influence). $\endgroup$
    – user24157
    Aug 14, 2019 at 17:35

1 Answer 1


I don't work with black holes, but I've been in the field of astrophysics for several years now, and until I read this question, I had never heard of either the two terms.

But a query on NASA/ADS, the primary database for "professional" astronomical papers (both refereed and non-refereed) yields 54 hits for "peribothron" vs. only 10 hits for "perinigricon". Not a lot.

As your links reveal, the etymological origin of peribothron/-nigricon is "near the black hole" in Greek and Latin, respectively. The reason has been to conform with terms such as perihelion, meaning "near the Sun". The first to use the Greek version in the literature was Frank & Rees (1976) who write in a footnote:

$^\star$We are grateful to W. R. Stoeger for suggesting this word, derived from the Greek bothros, a pit.

William Stoeger was the second author Martin Rees' student (and Stephen Hawking's classmate).

The first to use the Latin version seems to have been Schödel et al. (2002), but they don't offer any explanation for the term.

  • $\begingroup$ These don't fall under the same category as terms discussed in What's the origin and culture of funny astronomical terminology? but I wonder if the the opportunity to name something was so enticing that neither one could help themselves from coining a new term when the opportunity presented itself. Thanks for the answer! $\endgroup$
    – uhoh
    Aug 13, 2019 at 8:30
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    $\begingroup$ @uhoh You're welcome, was a fun one to dig into :) $\endgroup$
    – pela
    Aug 13, 2019 at 9:14
  • $\begingroup$ digging into my old questions I "discovered" that I hadn't accepted yet, so have done so now. Thanks again! $\endgroup$
    – uhoh
    May 10, 2020 at 2:00
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    $\begingroup$ @uhoh Thanks :) $\endgroup$
    – pela
    May 10, 2020 at 9:14

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