NGC 2685

{{short description|Lenticular and polar-ring galaxy in the constellation Ursa Major}}

{{Sky|08|55|34.7287|+|58|44|03.908}}

{{Infobox galaxy

| name = NGC 2685

| image = NGC 2685- A Helix in the Sky (iotw2415a).jpg

| caption = NGC 2685 imaged by the Gemini North Telescope

| epoch = J2000

| constellation name = Ursa Major

| ra = {{RA|08|55|34.7287}}{{cite web

| website=NASA/IPAC Extragalactic Database

| publisher = NASA and Caltech

| title=Results for object NGC 2685

| url=https://ned.ipac.caltech.edu/byname?objname=NGC+2685

| access-date=14 December 2024}}

| dec = {{DEC|+58|44|03.908}}{{r|ned}}

| z = 0.002945{{r|ned}}

| dist_ly = {{convert|14.79 ± 1.05|Mpc|Mly|abbr=on|lk=on|order=flip}}{{r|ned}}

| type = (R)SB0^+ pec{{r|ned}}

| size = ~{{convert|18.98|kpc|ly|abbr=on|lk=on|order=flip}} (estimated){{r|ned}}

| appmag_v = 11.3{{r|ned}}

| size_v = {{Val|4.6|×|2.5|u=arcminute}}{{r|ned}}

| names = {{odlist | name=Pancake Galaxy | name2=Helix Galaxy | Arp= 336 | UGC= 4666 | PGC= 25065 | 2MASX= J08553474+5844038 | MCG= +10-13-039 | CGCG= 288-012 | IRAS= F08516+5855}}{{r|ned}}

}}

NGC 2685 (also known as the Helix Galaxy) is a lenticular and polar ring Seyfert Type 2 galaxy in the constellation Ursa Major. Its velocity with respect to the cosmic microwave background is 1003 ± 9{{nbsp}}km/s, which corresponds to a Hubble distance of {{convert|14.79 ± 1.05|Mpc|Mly|abbr=on|lk=on|order=flip}}.{{r|ned}} Additionally, eight non-redshift measurements give a distance of {{convert|13.050 ± 0.924|Mpc|Mly|abbr=on|lk=off|order=flip}}.{{cite web | url = https://ned.ipac.caltech.edu/cgi-bin/nDistance?name=NGC+2685 | title = Distance Results for NGC{{nbsp}}2685 | website = NASA/IPAC EXTRAGALACTIC DATABASE | publisher = NASA | access-date = 14 December 2024}} It was discovered by German astronomer Wilhelm Tempel on 18 August 1882.{{cite web | url = https://cseligman.com/text/atlas/ngc26a.htm#2685 | title = New General Catalogue Objects: NGC{{nbsp}}2685 | last = Seligman | first = Courtney | website = Celestial Atlas | access-date = 14 December 2024}}

NGC 2685 is an object of great scientific interest, because polar-ring galaxies are very rare galaxies. They are thought to form when two galaxies gravitationally interact with each other. "The bizarre configuration could be caused by the chance capture of material from another galaxy by a disk galaxy, with the captured debris strung out in a rotating ring. Still, observed properties of NGC 2685 suggest that the rotating ring structure is remarkably old and stable."*{{Cite APOD|date=14 March 2014|title=Polar Ring Galaxy NGC 2685|access-date=2014-03-14}}

Allan Sandage referred to NGC 2685 as "perhaps the most peculiar galaxy in the Shapley-Ames Catalog".{{cite book|author=Sidney Van den Bergh|title=Galaxy Morphology and Classification|url=https://books.google.com/books?id=geEVkpueEPcC&pg=PA3|date=16 April 1998|publisher=Cambridge University Press|isbn=978-0-521-62335-3|pages=3}}