Malin 1

Malin 1 is a giant low surface brightness (LSB) spiral galaxy.^[1][5] It is located 1.19 billion light-years (366 Mpc) away in the constellation Coma Berenices, near the North Galactic Pole. It is one of the largest known spiral galaxies, with an approximate diameter of 650,000 light-years (200,000 pc),^[6][7][8] thus over six times the diameter of our Milky Way. It was discovered by astronomer David Malin in 1986 and is the first LSB galaxy verified to exist.^[5][8][6] Its high surface brightness central spiral is 30,000 light-years (9,200 pc) across, with a bulge of 10,000 light-years (3,100 pc).^[6] The central spiral is a SB0a type barred-spiral.^[6]

Malin 1
Image by the DESI Legacy Imaging Surveys, Data Release 10
Observation data (J2000.0[1] epoch)
Constellation	Coma Berenices [2]
Right ascension	12h 36m 59.34697s [1]
Declination	+14° 19′ 49.1585″ [1]
Redshift	0.082702±0.000013 [3]
Heliocentric radial velocity	24750±10 km/s [3]
Galactocentric velocity	24707±10 km/s [3]
Apparent magnitude (V)	15.809±0.009[3]
Absolute magnitude (V)	−22.01±0.50[3]
Characteristics
Type	SB0a [1]
Mass	~1012[4] M☉
Size	34.11 to 36.39 kpc (111,250 to 118,690 ly) (diameter; D25.0 B-band and 2MASS K-band total isophotes)[3][a]
Apparent size (V)	0.25′ × 0.23′[3]
Notable features	Surrounded by a H I disk
Other designations
PGC 42102, LEDA 42102, VPC 1091, 2MASX J12365934+1419494, Gaia DR2 3932516418935413504[1]

Malin 1 is peculiar in several ways: its diameter alone would make it the largest barred spiral galaxy ever to have been observed.^[4]

Malin 1 was found later to be interacting with two other galaxies, Malin 1B and SDSS J123708.91+142253.2. Malin 1B is located 46,000 light-years (14,000 pc) away from the high surface brightness central spiral of Malin 1, which may be responsible for the formation of the galaxy's central bar. Meanwhile, SDSS J123708.91+142253.2 is located within the huge, faint halo of Malin 1 and might have caused the formation of the extended low surface brightness disc through tidal stripping.

Observations by Galaz et al. in April 2014 revealed a detailed view of the spiral structure of Malin 1 in optical bands. The galaxy exhibits giant and very faint spiral arms, with some segments up to 33,000 light-years (10,000 pc) in diameter. Other details, such as possible stellar streams and formation regions, are revealed as well.^[9] The same authors also say that Malin 1 is larger than thought, with another estimated diameter of around 750,000 light-years (230,000 pc).^[9]

Gallery

• 
  Processed image of Malin 1 by Giuseppe Donatiello showing its weak spiral arms.
• 
  Malin 1 imaged in grayscale by the Hubble Space Telescope.

See also

• NGC 6872, large interacting barred spiral galaxy claimed in 2013 as largest spiral galaxy
• NGC 262, lenticular galaxy surrounded by a huge H I cloud discovered in 1885
• UGC 2885, a large unbarred spiral galaxy

Notes

1. The quoted diameter in this infobox was based on NED's provided scale "Virgo + GA + Shapley" of 1.811 kpc/arcsec multiplied with given angular diameters.