Gemini Observatory Captures Comet ISON

The three images on left are through an r-band filter only, and the color composite on right includes g, i, and r bands. All are integrated for 2 x 45 seconds with the February 4 image integrated for 2 x 75 seconds (increasing the comet’s apparent brightness). During the period of this sequence, the comet shined at about magnitude 15.5-16.5 in visible light. In these images north is up [need to flip image top/bottom] east is left, and the field-of-view is about 2.5 arcminutes across, which corresponds to about 270,000-290,000 miles (435,000-470,000 kilometers) at the distance of the comet. NASA’s Swift satellite and the Hubble Space Telescope (HST) have also imaged Comet ISON recently in this region of space. Swift’s ultraviolet observations determined that the comet’s main body was spewing some 850 tons of dust per second at the beginning of the year, leading astronomers to estimate the comet’s nucleus diameter is some 3-4 miles (5-6 kilometers). HST scientists concurred with that size estimate, adding that the comet’s coma measures about 3100 miles (5000 km) across. Color composite produced by Travis Rector, University of Alaska Anchorage. Credit: Gemini Observatory/AURA Composite , isophotes , analysis J.P.Navarro Pina ( Cometary Investigation Astrophysic Group_Facebook / NASA JPL )