As the Sun set on Memorial Day 2013, people were able to look to the west and see planetary neighbors Mercury, Venus, and Jupiter performing the celestial dance known as a planetary conjunction. Observers did not need any special equipment; the planets were bright enough for the human eye to suffice.
While an unobstructed view was necessary to catch the planets in their splendor—pollution does not count, as the light of the planets is bright enough to pierce through—all three bodies could be seen in this conjunction, also called a planetary trio. According to EarthSky.org, a planetary trio consists of any three planets that are less than 5 degrees from each other.
The current trio was less than 3 degrees apart on Monday night. Jupiter and Venus, which made up the two points at the base of a triangle, shone the brightest. Mercury, topping off the triangle, was somewhat less visible.
Conjunctions of this nature are reportedly rare, although the next time these three in particular will be this close together again will be in October 2015. The conjunction before was in 2011.
This conjunction will continue into next month. In fact, observers would have seen the trio forming an equilateral triangle on Sunday night just after sunset. Since the planets are continually moving, Monday’s representation was less accurate. Tuesday night the conjunction will be on display again with Jupiter and Venus appearing nearly on top on one another. Jupiter will start sinking closer and closer to the horizon as the conjunction continues into June. Venus and Mercury will climb higher.
The reason the planets all look much smaller than they actually are is because of their current position on the other side of the Sun. Even though Mercury appears fainter than its partners, it is the closet to Earth at 105 million miles distant. Venus clocks in at 150 million miles away; Jupiter is 565 million miles.
It is important to note that conjunctions are simply a matter of perception. It is indeed unique to see a handful of planets millions of miles away seemingly next to one another in the night sky, but one is in fact nowhere within proximity of another.
Some remarkable images have already documented this month’s conjunction, including a photo taken by astrophotographer Thierry Legault. Taken on Sunday, the image shows the French island Mont-Sanc-Michael with the trio of planets hovering in an equilateral triangle overhead. Equally stunning: the image captured by an amatuer photgrapher of the nation’s capital joined by the trio of planets in the background.