We’ve just passed the midway point of winter, which happened on February 3 at 4:11 p.m. Eastern Time. During this time, a beautiful pattern in the night sky called the “Winter Triangle” is visible in the southeast sky.
The Winter Triangle is made up of three bright stars, each from different constellations. The brightest is Sirius, which shines with a bluish-white light and sits in Canis Major, also known as the Big Dog. Next is Procyon, a yellow-white star in Canis Minor, the Little Dog. Procyon means “before the dog” in ancient Greek, as it rises before Sirius. Finally, there’s Betelgeuse, a reddish star in Orion the Hunter, known for changing brightness. Together, these stars create a nearly equilateral triangle that you can see in the evening sky.
Usually, this triangle is easy to spot, but this winter we also have a special addition to the sky.
In the eastern sky, around 6:30 p.m., look for a smaller triangle made by the stars Pollux and Castor, which are the heads of Gemini the Twins, and the bright planet Mars. Mars is currently the brightest of the three, so let’s call this the “Mars Triangle.”
The Mars Triangle features Mars at the top, shining in a brilliant yellow-orange light. Pollux and Castor form the base. The sides between Pollux and Mars, and Castor and Mars, are about 7 degrees long, while the Pollux-Castor side is around 4.5 degrees long. For comparison, your clenched fist at arm’s length measures about 10 degrees.
Unlike the fixed stars in the Winter Triangle, the Mars Triangle will change over the next weeks as Mars moves against the starry background. Since December 7, Mars has been moving backward, known as retrograde motion. When this started, it was in the neighboring constellation Cancer. Over the last few months, it has made its way into Gemini.
As it continues moving westward, the shape of the triangle will shift. On February 24, Mars will reach another stationary point, then switch gears and move east again. This will change the triangle’s appearance once more, forming a right triangle by March 10, with Pollux at the right angle. By April 9, Mars, Pollux, and Castor will align in a straight line again.
Keep in mind that, as Mars drifts farther from Earth, it will grow dimmer, decreasing from a brightness level of -0.6 to +0.6 by April 9. Although still bright, it will shine less intensely.
The apparent backward motion of Mars can be puzzling but can be understood through simple comparisons. As Earth overtakes Mars in its orbit, Mars appears to move backwards against the starry background. This phenomenon was first explained centuries ago by Nicolaus Copernicus, who clarified our understanding of planetary motion.
So, make sure to catch the Mars Triangle while you can! Enjoy the beauty of the stars, and maybe even grab a telescope to get a closer look at these celestial wonders.
