Castor and Pollux are often said to be twin stars, and they do have a nice similar appearance at first glance. Similar magnitude, but not exactly the same color. The biggest difference, however, is that only one is a visual double star, assuming you have a telescope. They are separated by only 7 arcsec, so a steady night and some magnification will help make the split.
Castor and Pollux Challenge (Telescope Moderate) May 2008 – Which of the “Twinsâ€
Castor and Pollux – Twins? May 2008
Almost forgot. We did this one at the observing field on Saturday, too. The crowd that followed me out there all agreed that Castor was the double star. We were sure it was Castor because Castor is closest to Capella, while Pollux is closer to Procyon.
We all agreed that the primary and secondary were yellow, but some folks saw some green along the edges of the primary. I suspect that it may have had to do with atmospherics, since none of my books shows a green component.
Now, what I did not know is that Castor is a visual triple, with the 'C' component looking like a field star, 71" out, or about 15-20 times further than the 'B' component. So, back to the telescope... Castor may be a six star system, since each component appears to have a spectroscopic companion.
We all agreed that the primary and secondary were yellow, but some folks saw some green along the edges of the primary. I suspect that it may have had to do with atmospherics, since none of my books shows a green component.
Now, what I did not know is that Castor is a visual triple, with the 'C' component looking like a field star, 71" out, or about 15-20 times further than the 'B' component. So, back to the telescope... Castor may be a six star system, since each component appears to have a spectroscopic companion.
Bob M
15" f5 Starsplitter Dob/80mm Finder
5" Explore Scientific triplet APO on a Vixen Sphinx GEM
________
"He numbers all the stars, and calls each one by name." Ps 147:4
15" f5 Starsplitter Dob/80mm Finder
5" Explore Scientific triplet APO on a Vixen Sphinx GEM
________
"He numbers all the stars, and calls each one by name." Ps 147:4