M44 (Praesepe or Beehive Cluster) in Cancer

Introduction

M44 is an open cluster in Cancer. To the Greeks it was known as Phatne. The Latin translation for Phatne is Praesepe, which means "manger". The Greeks and Romans saw this "nebula" as a manger, with "Asselli" (asses) eating from it, Assellus Borealis (the Northern Ass, 43 Gamma Cancri) and Assellus Australis (the Southern Ass, 47 Delta Cancri). Eratosthenes reported that these were the asses on which the gods Dionysus and Silenus rode into the battle against the Titans, who were frightened by the animals' braying so that the gods won. As a reward, the asses were put in sky together with Phatne. It is not known from where the other popular name, "the beehive" originated.

Historical observations

Aratos, a Greek poet was the first who recorded this beautiful open cluster as "A little mist" (260 BC). Other ancient recordings are from Hipparcos and Ptolemy. Hipparcos (130 BC) described it as "little cloud" or "cloudy star". Ptolemy in his Almagest (about 130 AD) called it "The nebulous mass in the breast (of Cancer).

Galileo was the first to resolve the cluster with the help of his telescope in 1609. He reported: "the nebula called Praesepe, which is not one star only, but a mass of more than 40 small stars".

When and where

Cancer reaches it culmination at midnight around the end of January. In mid-March it will pass through the meridian at 09.00pm. The Beehive is situated near the centre of Cancer, about halfway between Regulus in Leo and Pollux in Gemini. Cancer is a faint constellation. It's brightest star is Altarf (17-Beta Cancri) with magnitude 3.53. M 44 lies in the centre of Cancer, surrounded by an irregular rectangle formed by 47-Delta Cancri (3.9), 43-Gamma Cancri (4.7), 33-Eta Cancri (5.3) and 31-Theta Cancri (5.3). It can be spotted with the naked eye, though at a suburban site, you might have to use averted vision. With small binoculars you can identify Praesepe immediately.

What to expect

This object is best viewed with big binoculars or rich field telescopes. It's diameter is about 1.5 degrees, so a minimum field of view of three to four degrees will allow it to stand out nicely from it's surroundings. Personally I think an 11 or 12 x 80 would be very good. A rich field telescope using magnification of 25x will bring out more of the dimmer cluster members. Using the 32mm eyepiece on my telescope (8 inch F10) gives a FOV of 48 arc minutes. Only the centre of the cluster can be seen. You find an observation report and drawing of M 44 in the "Log-Section". The star map below shows M44 with stars plotted to magnitude 12.

M44 on the web

• For more information on M44 follow this link to the M44 page on the SEDS Messier Catalogue
• For observation-logs visit the NetAstro-catalogue. Search for Messier 44 and you will find more then 10 different log-entries on M44
• For a binocular observation go to Jere Kahanpää's site. Here you will find an observation of M44 with an 8 x 40 binocular. The observation is documented with a drawing of the object.

Bibliography

• Historical info and descriptions from "SEDS the Messier Catalogue"
• Finder chart with overview of constellation Cancer from "TheSky for Macintosh" by Software Bisque
• Detailed chart M44 and some data on M44 from "Skytools 2" by CapellaSoft
• The Deepsky, An Introduction by Philip S. Harrington
• Star-Hopping, your Visa to Viewing the Universe by Robert Garfinkle
• Binocular Astronomy by Crossen and Tirion
• Thee Night Sky Observer's Guide Volume 1 by Sanner and Kepple