Custos Messium

This constellation was invented in Early Modern Time by the French astronomer Joseph Jérôme de Lalande (1732–1807). Custos Messium is recognized as an 'extinct constellation' that fell into obscurity after the early 19th century.

Etymology and History

Origin of Constellation

Custos Messium as Vineyard Keeper in Young (1807). A Course of Lectures on Natural Philosophy and the Mechanical Arts.

Ian Ridpath writes:

This far-northern constellation was introduced by the French astronomer Joseph Jérôme de Lalande (1732–1807) on his celestial globe of 1775, and was described by him in an accompanying pamphlet titled Explication des nouveaux globes céleste et terrestre (see this review from the Journal des Sçavans of 1776 November). The name Custos Messium is a punning reference to his countryman Charles Messier, the famed comet hunter, and in fact the constellation was often known simply as Messier, particularly in France. Its brightest star was the present-day 50 Cassiopeiae, of 4th magnitude.

(...)

Lalande chose this previously anonymous area of sky because it was here that the comet of 1774 (now known as C/1774 P1) was first seen. The comet was extensively observed by Messier but, ironically, was not discovered by him – the discoverer in this case was actually another Frenchman, Jacques Laibats-Montaigne (1716–88).

The British scientist Thomas Young (1773–1829) renamed the figure the Vineyard Keeper on his chart of the northern hemisphere sky published in 1807 in A Course of Lectures on Natural Philosophy and the Mechanical Arts, but even this was not enough to broaden its appeal and it withered into obscurity.

John Barentine has a chapter on Custos Messium in Chapter 7 of his 2016 book "The Lost Constellations: A History of Obsolete, Extinct, or Forgotten Star Lore." Figure 8.10 of his book shows Custos Messium outlined in a modern star map.

Stars inside the Constellation

Some of the naked eye stars within the region of sky covered by Custos Messium include (in order of apparent V magnitude):

label	HIP	HD	description	IAU-name	Vmag
50 Cas	HIP 9598	HD 12216			3.95
BE Cam	HIP 17884	HD 2347			4.39
48 Cas	HIP 9480	HD 12111			4.49
gam Cam	HIP 17959	HD 23401			4.59
BK Cam	HIP 15520	HD 20336			4.74
ome Cas	HIP 9009	HD 11529			4.97
42 Cas	HIP 8016	HD 10250			5.18
49 Cas	HIP 9763	HD 12339			5.22
47 Cas	HIP 9727	HD 12230			5.27
40 Cas	HIP 7650	HD 9774			5.28
23 Cas	HIP 3721	HD 4382			5.42
21 Cas	HIP 3572	HD 4161			5.64
38 Cas	HIP 7078	HD 9021			5.82
SU Cas	HIP 13367	HD 17463			5.94
RZ Cas	HIP 13133	HD 17138			6.26
54 Cas	HIP 10031	HD 12800			6.57

The only star brighter than 4th magnitude in Custos Messium is 50 Cas (HIP 9598, HD 12216) a V=3.95 magnitude A2V main sequence star at distance 48 parsecs.

Transfer and Transformation of the Constellation

The name "Custos" (Latin for "guard") has been proposed as a proper name for a star in the vicinity of Custos Messium to be discussed by WGSN.

Mythology

no mythology.

References

• References (general)
• References (ancient Greco-Roman)
• References (medieval)