Epsilon Arietis: A Rewarding, Tight Binary in Aries

If you are looking for a good challenge to test your observing skills, Epsilon Arietis is a great target. This tight binary, also known as Struve 333, resides in the constellation Aries, an ancient and small constellation identifiable on autumn and winter nights.

The primary star is reasonably bright, with a magnitude of +5.2, making it easily visible with binoculars or a telescope from suburban locations. However, to see the magnitude +5.6 companion, you’ll most likely need a telescope with an aperture of four inches or greater. These two stars make a quaint pair, lying only 1.3 arcseconds apart. Both appear white and are A-type stars with a stellar classification of A2Vs. See the yearly orbit of the binary here.

A Long and Distant Dance

Epsilon Arietis isn’t just an optical illusion. The two stars are in a genuine, gravitational embrace, locked in a distant, majestic waltz. Their orbit is incredibly long, taking over 700 years to complete a single revolution. While we won’t see any noticeable orbital motion in our lifetime, the fact that they are a true binary system makes their observation even more meaningful. You’re not just looking at two stars that happen to be in the same line of sight; you’re witnessing a long-term cosmic partnership.

So, the next time you’re out with your telescope and the night sky is particularly clear, take a moment to hunt for Aries. Skip the well-known targets and seek out the subtle brilliance of Epsilon Arietis. It’s a reminder that sometimes, the greatest rewards in astronomy aren’t in the most obvious places, but in the quiet, challenging pursuit of a cosmic secret.

My Observations

This has to be one of the closest binaries I’ve ever split. I first viewed Epsilon Arietis with a 12mm eyepiece, seeing only the primary star, although it appeared elongated. I then attached my 2x Barlow and focused the scope, which split the splendid pair. They appear like two tiny white eyes looking back at me through the night.

Key Stats

Constellation	Aries
Best Viewing	Autumn & Winter
Visual Magnitude	+5.2 | +5.6
Separation	1.3″
Position Angle	210°
Spectral Class	A2Vs & A2Vs
Milky Way Location	Orion Spur
My Viewing Grade	A-
Designations	Struve 333, STF 333, Eps Ari, SAO 75673, HD 18519, HR 887, HIP 13914, 48 Ari

Sources and Notes

Stelle Doppie. (n.d.). 10584: Epsilon Arietis. Retrieved August 23, 2025, from https://www.stelledoppie.it/index2.php?iddoppia=10584

Sketch by Wayne McGraw