Planetary trio featuring Mercury, Venus and Jupiter as they appear after sunset on May 27.
Did you see the three planets after sunset last night? Jupiter, Venus and Mercury formed a near-perfect equilateral triangle in the western twilight sky. Tonight – May 27, 2013 – the triangle is not so equal-sided, but you can still witness the planetary trio that pops out over the western horizon about 45 to 75 minutes after sunset. Don’t miss these three planets! You’ll be looking over the sunset point on the horizon at evening dusk. Be sure to find an unobstructed horizon in the direction of sunset, and if you have them, bring along binoculars to enhance the view of the three planets.
By definition, a planetary trio refers to three planets that are less than 5o degrees apart from one another. The grouping at present is even more compact than that, with the spacing between planets at less than 3o.
A binocular field typically spans 5o of sky, so you should be able to view all three planets in a single binocular field at dusk and/or early evening. Venus is the most brilliant of the three, though Jupiter and Mercury are still respectably bright. Jupiter ranks as the second-brightest and Mercury the third-brightest.
Read more: Jupiter, Venus and Mercury now within a 3-degree circle
Although these planets reside on nearly the same line of sight, they are hardly close together in space. Astronomers oftentimes like to give the distances to the planets of the solar system in astronomical units (AU) – the average Earth/sun distance. As the planets come out this evening, their approximate distances from Earth:
Mercury, the solar system’s innermost planet: 1.1 AU
Venus, second planet outward from the sun: 1.6 AU
Jupiter, sixth planet outward from the sun: 6.1 AU.
A planetary trio is quite rare. The last one happened in May 2011 and the next one won’t take place until October 2015. However, last night’s view of Jupiter, Venus and Mercury was the closest we’ll see three planets until 2021.
Bottom line: On May 27, 2013, watch for a compact planetary trio as Mercury, Venus and Jupiter appear briefly in the deepening darkness after sunset. Look above the sunset point on the horizon.