The head of the Twins…(Photo by Author).
This week, we invite you to leave the telescope behind and instead hunt down a good binocular double in the constellation Gemini. Beneath the brighter stars of Castor and Pollux and near the star Iota Geminorum lies the wide pair 64-65 Geminorum, an often overlooked yellow-white pair. The angular separation of 13’ 38” makes it a well suited target for even small binoculars, and with a visual apparent magnitude of +5.0 each, a good naked eye test of sky conditions. 64, the right component, is 163 light years distant with a diameter of 2.3 solar radii, while 65 is 384 light years distant and monster at 26 solar radii. In addition, 65 is also a close spectroscopic double as well. The wide pairing is centered on the following coordinates;
Right Ascension: 7hours 30’ minutes.
Declination: +28° North.
The constellation Gemini also has a worthwhile open cluster M35 in the foot; catch it in the dusk before we lose the Twins behind the Sun in the coming months!
The astronomy word of the week is Optical Double. Notice the distance of the two stars above are drastically different? They only appear to be close together because they lie along our line of sight. Some doubles have short enough orbits that astronomers can actually see the change orientation over their human lifetimes; other associations are deduced by watching to see if the two stars share a common proper motion. Hate to break it to you, but another famous star party staple may well be a mere optical double as well, namely Albireo in the constellation Cygnus. The astronomical truth hurts sometimes, but it doesn’t diminish the beauty of these stellar objects!