65 Ursae Majoris (DN Ursae Majoris) -- Multiple Star System in Ursa Major
Three of Six
65 Ursae Majoris is located 2.5 degrees southwest of Taiyangshou (Chi Ursae Majoris). I like
this common name since it is Chinese meaning “Guard of the Sun”. Not many accepted star
names are Chinese, which makes Taiyangshou unique. The nearby six-star system of 65
Ursae Majoris is even more fascinating. With six stars it is almost an Open Cluster.
In the 155mm refractor I can only see three of the six stars. The primary star, in the drawing,
is really made up of four stars that are well below the ability of my telescope to separate.
Stars A1 and A2 eclipse each other every 1.73 days (orbital period) and this makes the
primary star also a variable star (named DN Ursae Majoris). In addition, there is a star (Ab)
that orbits around A1/A2 every 1.76 years. The fourth star (component B), is even further out
and orbits around A1/A2 every 118 years and has a separation from A1/A2 of 0.18
arcseconds (well below what my scope can separate). The stars C and D also belong to the
system but are much further out and within reach of my telescope. Their orbital times have
not yet been calculated but are in the order of thousands of years.
I see star “C” as yellow while the stars “A1/A2/Ab/B” & “D” as bright white.