Starwatch: See a 'Magnificent Planetary Gathering' This Week

By Gary A. Becker

StarWatch 874 for the week of May 19, 2013

Throughout this week three planets will be moving into position for what will become, early next week, the most stunning planetary grouping of the year.  

The assemblage takes place low in the west during evening twilight. The triad includes Mercury and Venus becoming more prominent because of their increasing distance from the sun, and Jupiter, which because of its slow orbital motion, will be overtaken and in conjunction with the sun on June 19.  

The week commences with the most difficult planet to see, Mercury, only nine degrees from the sun and setting about 52 minutes after sundown; Venus reaches the horizon only 15 minutes later. Jupiter, because of its distance from Sol, will pose no problem in viewing.  

Forty minutes after sundown, Venus will still be four degrees above the horizon, and Jupiter will be 10 degrees in altitude.  They should be easily seen if a good western horizon is available.  Scan just above the horizon 30 minutes after sunset.  Binoculars will help Venus and Jupiter stand out more easily against a bright horizon.  

By Saturday the scene will change completely. All three planets will be found in a tight little triangle about three degrees in diameter and six degrees above the horizon, 40 minutes after sundown. Binoculars will easily contain the three in the same field of view with ample space to spare.  

Venus will be brightest and lowest to the horizon, followed by Jupiter, which will be farthest to the left. Faintest and farthest to the right will be Mercury. All three members will be bright and easily visible to the unaided eye if sky conditions are transparent enough and the observing location unobscured enough to permit objects only a few degrees above the horizon to be seen.  On May 26, the grouping will be at its tightest with the largest separation among the three planets less than 2.5 degrees. 

May 27 finds Venus and Jupiter separated by just one degree. 

© Gary A. Becker—www.astronomy.org

Moravian College Astronomy