May 28 – June 10, 2018
Mount Washington — A note from a reader: “It is now 9 p.m. For the past few months, about this time in the evening, I view a very bright “planet.” I face west and this object is descending pretty quickly. Two months ago I figured it was Jupiter, now I am told Jupiter will not appear until a few more hours; in the early morning sky? It cannot be Venus as Mars (or any other planet) is nowhere nearby. Can you please tell me what this truly luminescent neighbor is?” –Doug
The experience of the questioner and the reasoning offered to prove that the bright celestial object he sees is not Venus both pique my interest and imagination. I identify with the act of looking to the west on clear evenings to marvel at the “Evening Star,” the most brilliant star-like body in Earth’s skies and an object of wonder since ancient times. I imagine that, initially, Doug thought the bright celestial light was Jupiter because planet Jupiter is the biggest planet in our solar system. Actually, smaller but more reflective Venus, our closest planetary neighbor, is brightest. Currently, Jupiter appears in the southeast as twilight deepens, rising above the opposite horizon from Venus (see ).
Doug conjectures that the riveting light in the west “cannot be Venus as Mars (or any other planet) is nowhere nearby.” Now it gets interesting! He must be picturing the solar system as we all have been taught to see it in our mind’s eye, the basic model of orbs of various sizes on rings that represent their positions in order out from the Sun. With this image fixed in our imaginations, it is reasonable to assume that this is the reality that would be projected onto the night sky — that all the planets would be there at the same time. Most of us are never prompted to think about the dynamic nature of the world, a world in which the planets move in their orbits in space at varying speeds and that the relationship between the planets changes.
Fourmilab is an ingeniously designed tool that allows us to make images of the changing relationships between the planets. To compare two calculations, see the illustration herein and look again at the one published two weeks ago.
Delights are multiplying for all who seek out views of the planets. Saturn, low in the southeast, to the right of the waning gibbous moon on May 31, joins Jupiter, south, in the nighttime sky. Astronomical twilight, or nightfall, is around 10:30 p.m. Note that Jupiter, -2.41 magnitude, is considerably brighter than .10 magnitude Saturn. Saturn rises about 10:30 p.m. tonight; 9:30 on June 10.
See the nearly full moon rise in the east-southeast tonight at 7:24 p.m. May’s Full Corn Moon, also known as Full Flower Moon, will be fullest to our eyes as it sets tomorrow morning, the 29th, at 5:40 a.m. in the southwest. Full phase is reached at 10:20 a.m. on the 29th, when moonrise is at 8:23 p.m. in the southeast.