By Dennis Herrmann
Among the best visual treats for skywatchers are the events called CONJUNCTIONS, in which two or more celestial objects appear to gather close together in the sky. These events happen because of the combined orbital motion geometries of the visual planets, the Moon, and the Earth itself (which positions us to view these events). Sometimes these orbiting bodies appear close to some first magnitude(bright) relatively fixed star. So within 12 hours on July 21 into July 22, two very nice conjunctions will happen for us.
As the Sun sets rather late in July, the planet Venus beckons in the western sky as darkness falls. It remains fairly low to the horizon however because the angle of the ECLIPTIC (the Sun’s apparent annual path through the zodiac; which is actually caused by Earth’s annual revolution (orbit) around the Sun), is low to the western horizon. Venus’s current orbital motion makes it appear to move south along the horizon without much gain in altitude all month. However the slender crescent Moon will help mark Venus to view on July 10th; the Moon being just 7 degrees from it. Venus will appear to move into the constellation of Leo, heading straight toward Regulus, the brightest 1st magnitude star in Leo. On the night of July 21st them, Regulus and Venus will be in conjunction; just a little over one degree apart.
The very next morning, July 22nd, Jupiter and Mars will be seen 45 minutes before sunrise and looking toward the east-northeast sky, and again, quite close to the horizon. The two planets will only be a degree apart and could be seen together in the same low power field of view of a small telescope; or also, through binoculars.
Saturn remains prominent for viewing in the evening southwestern sky all month at magnitude +0.6, appearing brighter than Spica, brightest star in Virgo, and left (east) of the bright star. Saturn does not set until after midnight. In the last week of July, Mercury will join Mars and Jupiter in the pre-dawn eastern sky. Look on the mornings of July 30 and 31, forty-five minutes before sunrise, Mercury will be lowest to the horizon and just below Mars, with Jupiter almost straight to the right of Mars. All three planets are found then at the top of Gemini. Castor and Pollux, the top two stars of Gemini will appear to the left of all three planets.
But remember, you will need a clear view to the eastern horizon. All 3 planets, Mercury, Mars, and Jupiter, though close to each other, will only be about 15 to 18 degrees above the horizon. This is quite low.
This time of year one of my favorite things to do is to scan with binoculars from the southern horizon upwards to the zenith and over toward the northeast horizon. In July and August this view will follow the main section of the summer Milky Way, which is toward the center of our galaxy. Binoculars always reveal an amazing view along this path including many more stars than one can see with the unaided eye, with a nice big field of view. In addition, star clusters, cloudy nebulae of cosmic gas, and even gaps, which look dark, and actually reveal dense gas clouds in the Milky Way are revealed. I have been doing this every summer since I was a boy and it has never gotten old.
Moon Phases in July: 1st quarter is July 15th; Full Moon July 22nd; and Last Quarter on July 29th. The New Moon will be July 8th.
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