Polar-ring galaxy

File:TPRG1137.jpg

A polar-ring galaxy is a relatively rare type of galaxy, with only around 100 examples known. The best known polar-ring galaxy is NGC 4650A. It is theorized that the structure of these galaxies result from the collision of two galaxies. The collision results in a structure composed of two rings of material rotating at an approximate right angle to each other.

Formation of polar-ring galaxies

File:Form-PRG.jpg

It is important to understand that the collision occurs so slowly that even over a lifetime, the movement is almost imperceptible. Also important is that once what is left of the interacting galaxy has gone on after the collision, the remaining static galaxy does not simply stop moving. The stars in the galaxy will continue on their new paths until they are dispersed and it is no longer a galaxy. What one sees when they look at a polar-ring galaxy is a freeze-frame of a former galaxy spilling out around itself, its stars destined to disperse over many light-years.

List of polar-ring galaxies

Category	Names of objects
Kinematically confirmed polar-ring galaxies	A 0136-0801, ESO 415-G26, Helix Galaxy, UGC 7576, NGC 4650A, UGC 9796
Candidates for polar-ring galaxies	IC 51, A 0113-5442, IC 1689, A 0336-4905, A 0351-5458, AM 0442-622, Abell 548-71,AM 063-371, UGC 5119, A 0950-2234, UGC 5600, ESO 503-G17, Abell 1631-14, Abell 1644-105, A 1256-1710, NGC 5122, UGC 9562, AM 1934-563, AM 2020-504, A 2135-2132, ESO 603-G21, A 2329-4102, A 2330-3751, A 2333-1637, A 2349-3927, A 2350-4042, ESO 293-IG17
Possible candidates for polar-ring galaxies	ESO 349-G36, A 00+2212, ESO 474-G26, A 0051-1323, AM 0051-234, NGC 304, ESO 113-IG4,ESO 243-IG19, NGC 442, ESO 152-IG3, NGC 625, UGC 1198, NGC 660, NGC 979, ESO 199-IG12, AM 0323-0430, A 0358-G20, ESO 358-G20, A 0323-0430, ESO 358-G20, A 0358-1707, ESO 201-IG26, A 0414-4756, ESO 202-G1, Abell 548-71, UGC 4261, UGC 4323, UGC 4332, NGC 2748, NGC 2865, UGC 5101, EGC 566-IG8, IC 575, ESO 500-G41, NGC 3384, NGC 3414, 3CR 249.1, UGC 6182, NGC 3934, NGC 4174, UGC 7388, IC 3370, NGC 4674, A 1247-2540, NGC 5103, NGC 5128, ESO 576-G69, A 1334-2935, ESO 326-IG6, A 1334-2935, ESO 326-IG6, NGC 6028, UGC 10205, NGC 6285+6286, ESO 232-G4, A 2015-7111, A 2027-2335, ESO 143-G37, A 2040-6210, A 2103-2532, NGC 7016, A 2104-2536, ESO 464-G31, A 2116-233, ESO 236-IG2, A 2132-2742, ESO 343-IG13, ESO 287-IG50, A 2150-1707, ESO 75-G55, A 2220-6617, NGC 7468, A 2304-3308, ZGC 2315+03, ESO 240-IG16, A 2358-2604
Objects related to polar-ring galaxies	ESO 79-G5, NGC 235, ESO 474-G11, ESO 296-G11, A 0153-3034, AM 0310-252, ESO 202-IG5,ESO 305-G21, AM 0529-442, A 0618-3633, ESO 16-G16, UGC 4892, NGC 3034, UGC 5485, NGC 3310, NGC 3406, A 1123-232, NGC 3718, NGC 3808, ESO 171 IG5, UGC 7636, NGC 4643, NGC 4753, AM 1257-222, UGC 8387, A 1356-2618, PG 163+658, NGC 6240, A 1837-6317, ESO 341-IG4, ESO 286-IG19, A 2102-2345, A 2111-5509, AM 2115-574, NGC 7252, A 2225-5838, ESO 146-IG29, A 2226-2459, ESO 109-IG23, ESO 239-IG2, A 2246-4909, NGC 7465
Typical examples of polar-ring galaxies (Boz, Peanut and X galaxies)	ESO 510-G13, NGC 520
Typical examples of polar-ring galaxies (Dust-lane eclipticals)	NGC 7625
Typical examples of polar-ring galaxies (Mayall-type objects)	NGC 5544+ NGC 5545
Typical examples of polar-ring galaxies (Smoke ring galaxies)	ESO 350-G40
Typical examples of polar-ring galaxies (Superpositions that resemble polar-ring galaxies)	NGC 3314 A 2256-0814
Typical examples of polar-ring galaxies (Theta Galaxies)	A 0103-3044
Typical examples of polar-ring galaxies (Hong-type objects)	A 1515+2146
Kinematically related	Milky way + Magellanic Stream, NGC 1068, NGC 1316, UGC 2892, NGC 3528, A 0609-331, NGC 2217, A 0632-629, A 0641-412, UGC 4519, A 1029-459, NGC 3998, NGC 4203, NGC 4262, NGC 4370, NGC 4546, NGC 5077, NGC 5194, NGC 5266, NGC 5745, NGC 5898, NGC 7007, NGC 7097

• Polar Ring Galaxy NGC 2685

References

• Hubblesite.org Retrieved January 2007

External links

• An image of NGC 4650A, a Polar Ring Galaxy