Look up to See Two Bright Celestial Triangles This Month
There are several bright star patterns visible in the winter sky this month, including a triangle with Mars at one point, so it’s worth braving winter temperatures for stargazing.
These shapes are not constellations, but asterisms : groups of stars that form recognizable patterns but do not have an official International Astronomical Union location. For example, Ursa Major and Ursa Minor are asterisms, although their stars are included in the constellations Ursa Major and Ursa Minor.
The winter triangle, which is especially visible right now, consists of the stars Sirius, Procyon and Betelgeuse, which are located in the constellations Canis Major, Canis Minor and Orion, respectively. And this asterism is part of an even larger asterism known as the Winter Circle (or Winter Hexagon) , which is also visible in the winter sky from December to mid-April.
Over the next few weeks (until about mid-March), another triangle will illuminate the night. “Mars Triangle” is an even less official form, technically not a true asterism, and the name was suggested by Space.com . If you combine Mars with Pollux and Castor, both from the constellation Gemini, you get a smaller isosceles triangle with the Red Planet as the brightest of the three points. This triangle will slowly shift as Mars moves relative to the fixed stars until they all line up in a straight line in early April. Unlike asterisms, the so-called Martian triangle is temporary and constantly changing.
Where (and when) to look for the Winter and Martian triangles
The Winter Triangle is visible in the Northern Hemisphere until the end of this month. Look high in the southeastern sky, near Orion’s belt , after sunset. Sirius, the brightest of the three stars, will appear first, followed by Procyon and Betelgeuse. The triangle will be visible until the early morning when it will set to the west-southwest. (The winter triangle appears in the Southern Hemisphere between May and August.)
To see the Mars Triangle, Space.com suggests looking east around 6:30 p.m. local time. Mars is the brightest point and is currently the apex of the triangle, with Castor and Pollux forming the base. The triangle will be visible until about mid-March, although again its shape will change significantly over time.
The Winter Circle , which includes Sirius and Procyon (from the Winter Triangle), Castor and Pollux (from the Mars Triangle), and Rigel, Capella and Aldebaran, rises in the east and sets in the west throughout the winter.