Inferior Conjunction of Venus – June 2020

by Venus Observer, Milan B.

In two days (June 3rd, 2020), our twin sister planet will pass between us and the Sun. This brings fond memories of the similar passes in June 2004 and June 2012, which both resulted in transits across the solar disk, but this time around, Venus will just miss the solar disk by a quarter of a degree on its passage from northern to southern ecliptic latitudes.

Conjunction of Venus with the Sun on June 3rd, 2020, courtesy of Sky Safari

This 8 year cycle of Venus was known even to ancient Mayas. In 8 Earths years, Venus will make 13 orbits around the Sun and since both planets orbit the sun in the same direction, there will be 13 – 8 = 5 synodic periods of Venus looking from planet Earth. Any Fibonacci fans out there?

During 5 synodic periods Venus will go through 5 inferior conjunctions. Only one of these five is close to the Sun in the current epoque, two will be midway to the maximum distance which is just under 9 degrees and the remaining two will be very close to the maximum angular distance from the Sun.

5 synodic periods of Venus actually falls short of 8 years by 2 and a half days. With this, all inferior conjunctions will slowly move earlier in the year within each series. The 2020 conjunction, happening on June 3rd, is part of the June-May series, as was the 2004 transit, which occurred on June 8th and the 2012 transit, which occurred on June 5th.

With this years conjunction being a near miss, the question becomes: when will Venus next be so close to the solar disk? The visualisation below shows about 130 years of inferior conjunctions and each of the five seasons is labelled by the pair of months that it occurs in during the 21st century.

130 Years of Inferior Conjunction of Venus with the Sun, courtesy of Milan B. and Tableau

As the Jun-May series conjunctions (the green series above) are slowly moving away from the Sun and will not result in any transits for many centuries, we will need to turn to another series to bring us the next sequence of close passes and transits. The Jan-Dec series conjunctions, which are currently far from the solar disk are slowly inching (in astronomical terms) towards the Sun and also regressing from mid January (in early 2000’s) into early December (in the early 2100’s) which will result in another pair of transits, this time the December transits of 2117 and 2125.

Venus one week after the 2015 Inferior Conjunction, Aug 22nd 2015, courtesy of Milan B. and SkyWatcher.

From the chart above it becomes apparent that after the June 2020 conjunction, Venus will not venture so close to the Sun (from Earths perspective) for another 97 years, until the 2117 transit. Hopefully, some of the younger generations will get a chance to see this remarkable astronomical event.