Polaris and the Diamond Ring

Many treasures await the binocular observer that are either not seen, or if seen not appreciated, telescopically, or with the naked eye.  One of these is the “diamond ring” asterism in Ursa Minor.  Point a pair of binoculars at Polaris any evening, and you’ll notice that Polaris is the “diamond” astride a ring-shaped circlet of stars.  Sweet!

The twelve stars that make up the diamond ring include one second magnitude star (Polaris 2.0), one sixth magnitude star (HR 286 6.5), four eighth magnitude stars (HD 8395 7.9; HD 14369 & HD 11696 8.1; HD 18365 8.5), and six ninth magnitude stars (HD 14718 8.6; HD 12364 & HD 17376 8.8; SAO 223 8.9; SAO 214 9.0, SAO 508 9.1)—perfect for binoculars!  Here are their distances, in light years.

Of course, there are uncertainties in each distance, so the actual distance to each star is probably within the range shown below.  You’ll notice that generally, the farther away a star is, the greater is the uncertainty in its distance.

Our best guess, then, for when the light we are receiving tonight left each star is shown below.

Due to uncertainty in each trigonometric parallax, more properly we should list a date range when the light left the photosphere of each star, shown below.