If you look up this week, to the southwest, you’ll see a bright star in the evening twilight that, upon close inspection, is really a tight double star. The fainter companion becomes obvious as it gets dark. The bright member of the pair is actually Saturn, and its fainter companion is the star Porrima, a.k.a. Gamma Virginis. And they are unusually close!
This week Saturn (at bottom here) sidles up to Porrima (at top), getting so close both are contained in a high-power telescope field, which is what this shot depicts. I took it Saturday night, June 4, when Saturn was about 1/4° (16 arc minutes) from Porrima. But by June 10 their separation will be a tad less, at 15 arc minutes apart. This week Saturn stops its annual retrograde motion just shy of Porrima.
The pairing made a wonderful sight in the telescope tonight, especially because of the “good seeing” — so Saturn looked very sharp. And Porrima, itself a very tight double star, was easy to split at 200x, appearing like a pair of headlights at high power. (The photo doesn’t split Porrima.)
But the nicest view is just naked eye — Saturn and Porrima are forming a rare and temporary double star easy to split with no optical aid but looking much more striking than any other naked eye double. The pairing won’t last long — Saturn turns around near Porrima this week, then begins to head east again away from its stellar partner.
The shot also picks up four of Saturn’s moons: Dione very close to Saturn, then Tethys, and Rhea in a row from left to right, and bright Titan below the trio.
This a stack of five 5-second exposures at ISO 1600 with a Canon 7D attached to my 130mm Astro-Physics refractor with a 2x Barlow, giving an effective focal length of about 1600mm and f/12. I took this in twilight to add the blue sky.
— Alan, June 5, 2011 / Image © 2011 Alan Dyer