Siamese Twins (NGC 4567/8)
History
The two galaxies were discovered on 15 March 1784 by William Herschel. As for most of his discoveries he was using his 18.7 inch reflecting telescope with 20 feet focal length. He cataloged them as IV 8 and IV 9 (class IV = planetary nebulae, stars with burs, with milky chevelure, with short rays, remarkable shapes, etc.) He described as «a double nebula. The chevelure run into each other. close. not very faint.» In 1888 Dreyer added those two objects as NGC 4567 and NGC 4568 to his famous catalog. [463]
Physical Properties
The pair of galaxies is also known as butterfly galaxies because they look like such a flapping of wings. These are galaxies that are circa 6 kpc close together and it has been discovered, that they show a warmer and denser gas tracer in the overlapping region, which indicates an early stage of interaction. The interaction has not yet destroyed the inner spiral structures of NGC 4568 and NGC 4567, but does affect the outer stellar disk. [611, 612]
| Name | RA | Dec | Type | bMag | vMag | B-V | SB | Dim | PA | z | D(z) | MD | Dreyer Description | Identification, Remarks |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NGC 4564 | 12 36 26.9 | +11 26 23 | Gx (E6) | 12.1 | 11.1 | 1.0 | 12.9 | 3.5 × 1.5 | 47 | 0.003809 | 16.09 | 16.120 | pB, S, lE, psbM | WH II 68; h 1356; GC 3105; UGC 7773; MCG 2-32-150; CGCG 70-186; VCC 1664 |
| NGC 4567 | 12 36 32.7 | +11 15 28 | Gx (Sbc) | 12.1 | 11.3 | 0.8 | 13.1 | 3.1 × 2.2 | 85 | 0.007495 | 31.66 | 25.550 | vF, L, np of D neb, pos 160° ± | WH IV 8; h 1358=1363; GC 3108; UGC 7777; MCG 2-32-151; CGCG 70-189; IRAS 12340+1130; VCC 1673; VV 219; KCPG 347A; Siamese twins |
| NGC 4568 | 12 36 34.2 | +11 14 19 | Gx (Sbc) | 11.7 | 10.8 | 0.9 | 13.1 | 4.6 × 2.2 | 23 | 0.007522 | 31.77 | 20.930 | vF, L, sf of D neb, pos 160° ± | WH IV 9; h 1359=1363; GC 3109; UGC 7776; MCG 2-32-152; CGCG 70-188; IRAS 12340+1130; VCC 1676; VV 219; KCPG 347B; Siamese twins |
| IC 3578 | 12 36 39.5 | +11 06 05 | Gx (Sc) | 15.1 | 14.4 | 0.7 | 12.8 | 0.9 × 0.3 | 135 | 0.002323 | 9.81 | S, E 125° | UGC 7782; MCG 2-32-153; CGCG 70-190; VCC 1684 |
Finder Chart
The galaxy pair can be found in the Virgo constellation in the Virgo cluster. Connect the stars Vindemiatrix (ε Virginis, 2.8 mag) and Denebola (β Leonis, 2.1 mag). Position the Telrad in about the first third so that the middle Telrad circle comes below the connecting line and the 4.9 mag star ρ Virginis comes between the outer circles. The pair of galaxies is located about half a degree southwest of Messier 58. Not far from there is a pair of stars of about the same brightness of about 12th magnitude.
Visual Observation
350 mm aperture: With 11.3 mag and 10.8 mag the two glaxies can already be found in smaller telescopes. Both have a bright core and are elliptical in shape. They appear to be touching at the ends. However, the latter can only be seen with certainty with a medium-sized aperture. [192]