Planets in the Evening / The Winter Triangle in Spring

The western sky just after sunset is exploding with beauty and it is well worth the time to spend a few minutes soaking it in. Right now there are three planets on display in the evening sky along with the fine winter constellations still visible as the glow of dusk fades. I have been watching this over successive evenings and am impressed with the variety of colors and patterns visible after sunset. This week the sun drops below the horizon around 8:00 PM pacific daylight time and the sky is reasonably dark by 8:30, but by 9:00 the best viewing emerges.

First up is the fast-moving planet Mercury which will spend the next few weeks making a strong showing in the western sky. Because it is so close to the sun it never moves far above the horizon, but we will be seeing it at one of the best views of the year. This diagram shows Mercury in a close encounter with the Pleiades on May 1st, but it will continue to hover in the west through mid-month. It is bright enough to be seen in the glare of the dusk sky and you will see it best if you have a clear western horizon.

Next is Mars which continues to share the limelight with the twin stars of Gemini, Castor and Pollux. Mars is distinctive in comparison to the Twins because of its deep orange color. It is slowly diminishing in brightness but is still bright enough to be easy to find.

Saturn is the highlight of the planetary lineup, high in the sky after sunset in the constellation of Leo. More on Saturn can be found in my last post.

The bright constellation Orion is now setting in the glare of sunset, slowly fading from view as the constellations of summer arrive in the east and begin their reign. Nonetheless, a very bright grouping is still visible in the western sky featuring three stars from three different constellations. A distinctive grouping of stars from different constellations is known as an "asterism" and the Winter Triangle is one of the more distinctive asterisms in the sky. It contains Sirius, the brightest star in the sky which is in the constellation Canis Major, Procyon, the brightest star in Canis Minor, and Betelgeuse, which is in the constellation Orion. This diagram provides a helpful guide to this pattern. Each of these stars have distinctive colors, with Betelgeuse an orange-red (it is a red giant star), Sirius whitish-blue, and Procyon in-between the two as a plain white star. Enjoy the sky this spring - it's full of remarkable things to see.