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Like all bodies in the solar system the planets are continually moving as they orbit the Sun. When viewed from Earth an ever changing scene results as they dance on their merrily way against the backdrop of the fixed stars. Quite often two planets will appear very close together in the night sky, a planet will pass in front of a distant star or one will briefly obscure the light of a beautiful open cluster. These conjunctions and occultations can be spectacular events, rewarding for visual observers and excellent opportunities for imagers to capture a stunning photo.

One such event will take place from the 30th September until the 3rd October 2011. During this time the red planet Mars will move almost exactly through the middle of M44 the famous Beehive or Praesepe open cluster.

Beehive Cluster

M44 is a large and bright showstopper open cluster. At apparent magnitude 3.4 it is easily visible to the naked eye as a nebulous patch, particularly when viewed from a dark site. Since the Beehive is a large cluster covering over 1½ degrees of sky, three times the diameter of the full moon, it is best observed with binoculars or a wide field telescope. Binoculars reveal tens of mainly white stars with a noticeable grouping in the shape of a "V" just off center. It is also a great sight in a 100mm (4-inch) telescope at 35x magnification. Here the cluster nearly fills the complete field of view with at least 50 bluish coloured stars brighter than 9th magnitude visible. The majesty of the Beehive is lost a little in larger scopes as they struggle to contain its large size but is anyway still a nice sight.

M44 Beehive or Praesepe Open Cluster (NOAO/AURA/NSF)

The brightest stars in M44 are of 6th magnitude and it is one of the closest open clusters to Earth at a mere 577 light-years (177 parsecs).


To find the Beehive cluster look to the heart of the faint zodiac constellation Cancer. Here there is a quadrangle of stars formed by Asellus Australis (δ Cnc), Asellus Borealis (γ Cnc), η Cnc and θ Cnc. All of these stars are between 4th and 5th magnitude and M44 lies at the centre of this grouping.

Mars conjunction

The conjunction between Mars, apparent magnitude 1.3, and M44 starts on the 30th September. At this time the red planet enters the western edge of the cluster, travels in a SEE direction before reaching the mid-point of M44 the next day. Another day later and Mars proceeds to exit on the opposite side of the cluster and the conjunction is almost over. The whole process takes just under three days from beginning to end.

Cancer star chart showing Mars moving through M44

Cancer star chart showing Mars moving through M44 - pdf format

At this time of a year Mars is a morning object, rising around 1 to 2 am depending on where you live. The best views are probably an hour or two before sunrise when Mars will be relatively high in the sky (at least for Northern hemisphere observers).

Mars Data Table

Date Time (UT)RA (J2000)DEC (J2000)Apparent Magnitude Illumination (%)Constellation
28 Sep 2011 - 00:0008h 31m 30.57s+20d 00m 02.2s1.3191.879Cancer
29 Sep 2011 - 00:0008h 33m 59.50s+19d 52m 03.8s1.3191.826Cancer
30 Sep 2011 - 00:0008h 36m 27.79s+19d 43m 59.7s1.3091.774Cancer
01 Oct 2011 - 00:0008h 38m 55.43s+19d 35m 50.2s1.3091.722Cancer
02 Oct 2011 - 00:0008h 41m 22.42s +19d 27m 35.4s1.2991.671Cancer
03 Oct 2011 - 00:0008h 43m 48.74s+19d 19m 15.4s1.2991.619 Cancer
04 Oct 2011 - 00:0008h 46m 14.42s+19d 10m 50.3s1.2891.568Cancer
05 Oct 2011 - 00:00 08h 48m 39.43s+19d 02m 20.4s1.2891.518Cancer
06 Oct 2011 - 00:0008h 51m 03.79s+18d 53m 45.7s1.27 91.467Cancer