Delta Cancri - History

History

Delta Cancri was involved in the first recorded occultation by Jupiter:

"The most ancient observation of Jupiter which we are acquainted with is that reported by Ptolemy in book X, chap. iii (sic), of the Almagest, ...when the planet eclipsed the star known as (Delta) Cancri. This observation was made on September 3, B.C. 240, about 18h on the meridian of Alexandria." —Allen, 1898, quoting from Hind's The Solar System).

Delta Cancri also marks the famous open star cluster Praesepe (or the Beehive Cluster, also known as Messier 44). In ancient times M44 was used as a weather gauge as the following Greek rhyme from Aratos' Prognostica reveals:

A murky manger with both stars

Shining unaltered is a sign of rain.

While if the northern Ass is dimmed

By vaporous shroud, he of the south gleam radiant,

Expect a south wind: the vaporous shroud and radiance

Exchanging stars harbinger Boreas. —Allen, 1898

The meaning of this verse is that if Asellus Borealis or Gamma Cancris is hidden by clouds, the wind will be from the south and that situation will be reversed if Arkushanangarushashutu is obscured. There is some doubt however as to the accuracy of this as Allen notes: "Our modern Weather Bureau would probably tell us that if one of these stars were thus concealed, the other also would be." (Allen, 1898)