UGC 1840

UGC 1840
UGC 1840 imaged by the Hubble Space Telescope
Observation data (J2000 epoch)
Constellation	Andromeda
Right ascension	02h 23m 08.4268s[1]
Declination	+41° 22′ 20.031″[1]
Redshift	0.018096
Heliocentric radial velocity	5,420 km/s
Distance	258.5 Mly (79.1 Mpc)
Characteristics
Type	Peculiar
Size	~131,100 ly (40.20 kpc) (estimated)
Notable features	Collisional ring galaxy
Other designations
IRAS 02200+4108, 2MASX J02231142+4122047, Arp 145, MCG +07-06-002, PGC 9060 & 9062, CGCG 538-056, HFLLZOA F264, V Zw 229

UGC 1840, also known as Arp 145, are a pair of interacting galaxies located 250 million light-years away from the Solar System in the Andromeda constellation.^[2] The earliest known reference to the pair of galaxies is in part 2 of the Morphological Catalogue of Galaxies, published in 1964, where it is listed as MCG +07-06-002.^[3]

Made up of two galaxies, UGC 1840 NED01 (PGC 9060)^[4] and UGC 1840 NED02 (PGC 9062),^[5] the two galaxies had recently collided with each other^[6] in which the elliptical galaxy has penetrated through the spiral galaxy's nucleus leaving a hole in its middle, thus forming a ring galaxy.^[7][8] With a diameter of 1.3 arc minutes, close to 100,000 thousand light-years, they are roughly the same size as the Milky Way.^{[9][unreliable source?]}

Both galaxies are listed as Arp 145 in the Atlas of Peculiar Galaxies which was created by Halton Arp.^[10][11] They fall under the category of objects that have emanating material and both classified as galaxies that have ring systems.