Lunar Conjunctions and Globular Clusters in June

by Rod Kennedy

June 2010 Skychart [PDF]

Astronomy is one of the few sciences that also doubles as a hobby. Like most scientific
hobbies, astronomy is rooted in observation, which tends to lead to questions, which in turn
leads to research, which leads to further observations. Some observations, such as
conjunctions of the planets and the moon, require no special equipment. Others, such as
observations of deep sky objects require observational aids such as binoculars or telescopes
as well as knowledge of the objectʼs position in the sky. June offers sky watchers a chance to
observe both planetary/lunar conjunctions as well as the mysterious deep sky objects known
as globular clusters.

The third-quarter moon passes the planet Jupiter on the morning of June 6th. This conjunction
will be fairly obvious in the pre-dawn sky due to the brightness of Jupiter. Telescope users
focusing on Jupiter will also get a bonus during the first week of June. The planet Uranus will
be within half a degree to the northeast of Jupiter. Small telescope users may only see a small
bluish dot, similar to a bright star. Telescopes of 8 inches or larger in diameter may be able to
discern the disk of the planet. On June 11th a very slim crescent moon passes the planet
Mercury but binoculars will most likely be needed to pick them out of the glare of the sun. By
the evening of June 14th the moon has moved around the Earth and is now waxing in the
evening sky. On the 14th a slim waxing crescent moon passes the planet Venus. The moon is
fairly close to the planet Mars on the evenings of the 16th and 17th and Saturn on the evening
of the 18th.

June is the best month to observe the constellation of Ophiuchus, the Serpent Bearer.
Although June nights are short compared to other times of the year, it is the time when
Ophiuchus is in the sky for the entire night. While Ophiuchus does not contain many bright
stars, it does contain 3 beautiful examples of globular clusters. Globular clusters are densely
packed clusters of stars that reside in the halo of galaxies. They are generally spherical in
shape and contain hundreds of thousands of very old stars. Ophiuchus contains 4 fairly bright
globular clusters, all discovered by Charles Messier within a few nights in 1764.
M9 is found just south of the star Sabik, in the southeast corner of the constellation. The stars
of M9 are fairly densely packed although M9 is the smallest of the four. M10 and M12 are just
3.4 degrees apart within the central “coffin” asterism of Ophiuchus. Their close proximity
means they should both be easily visible in binoculars or a telescope with a low magnification
eyepiece. M10 is a fairly rich bright cluster while M12 is slightly dimmer. M14 is on the
eastern edge of the constellation about two thirds of the way from the star Sabik to Cebalrai.
Unlike most globular clusters M14 does not have a clearly defined central core of stars. In
addition it is slightly elongated at the edges.

Amateur astronomy is one of the original scientific hobbies. Enthusiasts of this hobby take
great pride and pleasure in knowing they are observing the same objects as professional
astronomers around the world. While the average amateur may not have the same level of
sophisticated equipment as a professional, they still pursue the science with the same vigor,
and June is a perfect time to renew that passion for the sky.

Rod Kennedy is a technician at the Casper Planetarium. He can be reached at 307-577-0310 or

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