OBSERVER’S CHALLENGE – MARCH, 2021
by Glenn Chaple
NGC 2685 – Lenticular Galaxy in Ursa Major (Mag: 11.3, Size: 4.6’ X 2.5’)
This month’s Observer’s Challenge, NGC 2685, is a lenticular galaxy with a twist. It has a ring of stars, gas, and dust that runs perpendicular to the plane of the main galactic disk. Such rarities are known as polar ring galaxies. These cosmic oddities are likely a result as a collision or gravitational interaction between two galaxies, one of which is lenticular. The appearance of the whorls surrounding NGC 2685 give it the nick-name the “Helix Galaxy,”
Those with computer-controlled scopes will find NGC 2685 at coordinates RA 8h 55m 34.8s, Dec +58° 44’ 03.9”. If you locate deep sky objects via the star-hop method, begin your search at the 3rd magnitude star Muscida (omicron [ο] Ursae Majoris), shown in upper right of Chart A. Aim your telescope midway between Muscida and 5th magnitude 17 Ursae Majoris (Chart B), and you should come across a pair of stars of magnitude 6 and 7 that are about a degree apart. Chart C shows the location of NGC 2685 between these two stars.
NGC 2685 was discovered by the German astronomer Wilhelm Tempel on August 18, 1882. Studies indicate a distance of around 40 million light years and a visual diameter of some 50,000 light years- about half that of the Milky Way.
Finder Charts for NGC 2685
www.constellation-guide.com (from IAU and Sky and telescope)
Taki’s magnitude 8.5 Star Atlas (takitoshimi.starfree.jp)
Glenn Chaple (from AAVSO Variable Star Plotter) Field is 3° by 1° with north up. Stars shown to 11th magnitude
NGC 2685 Image by Mario Motta, MD (ATMoB) Taken with 32-inch f/6.5 telescope with ZWO ASI6200 camera, 3 hours imaging, using RGB and Lum filters, processed in Pixinsight.