July begins with the moon just past third quarter, and new moon is July 8. This is an exact repeat of last month, which should come as no surprise, since the original word was "moonth."
The moon orbits the Earth in about 29 days (29.5 days), approximately the length of one month. Note the use of "about" and "approximately," because the lunar orbit is complicated. For one thing, like all planetary bodies, the moon travels in an elliptical orbit and is non-circular. Thus we get some apparitions appearing larger than others, because the moon is closer to the Earth at some times and further away at others. Watch for close approaches of Mars July 6, Venus July 10, Spica (an occultation in the south) July 15, and Saturn July 16. The moon is full July 22.
Mercury is hidden in the sun's glare until late in the month, when it appears in the dawn sky. Photographers may want to note a close grouping late in the month of Mercury, Mars, and Jupiter, all within the constellation Gemini. Mercury's orbital period is about 88 days.
Venus remains in the western evening sky; in the Beehive (M44) July 2, meeting up with the moon July 10 and Regulus July 21. The bright planet orbits the sun in about 224.7 days.
Mars rises in the eastern dawn, passing near the star cluster M35 July 16, and Jupiter July 22 (see above for three planets in a row). Mars orbits the sun every 687 days.
Jupiter rises in the eastern dawn early in July, brushing by the cluster M35 July 5. See also Mercury above. The giant planet's orbital period is 4332.6 days (about 12 years).
Saturn is found in the western evening sky, setting near midnight. It has been retrograding in June and early July, and begins prograde motion July 9. Saturn's period is 10,759.2 days (29.4 years).
Uranus appears near midnight, crossing the sky until dawn, which comes early during the summer months. The blue-green gas giant orbits the sun every 30,799 days (84.4 years).
Neptune rises in late evening, also retrograding, and orbiting every 60,190 days (164.8 years).
The south delta-Aquariid meteor shower peaks July 29, although observers may see its signs from mid-July to mid-August. Look for the radiant near the bright star delta-Aquarius (of course).
- James Edgar has had an interest in the night sky all his life. He joined The Royal Astronomical Society of Canada in 2000 and is editor's assistant and a contributor to Observer's Handbook, production manager of the bi-monthly RASC Journal, and the society's national secretary. He was given the RASC Service Award at the 2012 General Assembly in Edmonton.
