NGC 864

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NGC 864 is an isolated, star-forming spiral galaxy in the Cetus constellation. It’s classified as an intermediate spiral with a central bar and a hint of a ring, and its outer arms appear somewhat lopsided. Discovered by William Herschel in 1785, it has been studied to understand how such galaxies form and evolve.

In 2012, astronomers at the Roque de los Muchachos Observatory used high-resolution H-alpha imaging with ACAM and the GHαFaS instrument on the William Herschel Telescope to map NGC 864’s gas and test a new flux-calibration method. They found a bar with bright star-forming regions at its ends and two asymmetric spiral arms. The outer spiral is a flocculent pattern, though some scientists consider it grand-design. The galaxy’s notable asymmetry is especially interesting because it is isolated; it’s unlikely to be caused by a recent galaxy collision. Some researchers think internal dynamical instabilities could be responsible, while others suggest a minor companion near the edge of the gas disc might have crossed the plane, causing the observed warp.

Key data:
- Coordinates (J2000): RA 02h 15m 27.64s, Dec +06° 00′ 09.4″
- Redshift: z = 0.005210
- Heliocentric velocity: 1562 km/s
- Distance: about 22 million parsecs (roughly 72 million light-years)
- Apparent magnitude: V 10.9, B 11.4
- Type: SAB(rs)c
- Other names: UGC 1736, PGC 8631, CGCG 413-066, MCG +01-06-061, IRAS 02128+0546, KUG 0211+276, 2MASX J02152764+0600094, CN 510