Starwatch: Planetary Dance Continues

By Gary Becker

The astronomical story of this week still focuses on the WNW as Mercury and Venus play in the bright twilight of late spring evenings.  Mercury remains in the lead all week, but if you watch it from night to night, it will begin to slow in its motion as it shortly begins its trek toward the sun.  

It is farthest from the sun on June 24 when it is at its greatest angular distance east of the sun, but its altitude and brightness will have decreased substantially by that time.  

Even during the week of June 9, binoculars are strongly recommended to see Mercury clearly.  Go outdoors about 45 minutes after sundown and look towards the WNW in the same area of the sky as sunset.  The most important consideration will be an unhindered western horizon.

Venus should be easily seen with just the eye, even during hazy conditions. During the first few days of the week, view Venus using binoculars. Then scan less than one full field of view to the left and above Venus to spot much fainter Mercury.

Monday and Tuesday—June 10-11—bring a thin waxing crescent moon with plenty of earthshine to add luster to the dimming twilight hour. The moon will be to the left of Mercury and Venus.  

As the week unfolds, Venus and Mercury will be closing on each other. Mercury will appear to be circling counterclockwise around Venus by the end of the week.  

The week of June 16 positions Venus and Mercury less than three degrees apart, and this close twirl continues through the summer solstice on June 21, as Mercury dips below Venus and heads towards the horizon.  

On June 19, both planets are nearly horizonal to the horizon.  Mercury will be to the left of Venus and less than two degrees apart, an easy view through binoculars, especially because of Venus’ brightness.  

By the onset of the week of June 23, Mercury exits the scene leaving only Venus as the sole guardian of the west after sundown.