UGC 5470, Leo I

History

Due to its proximity of only 12 arc minutes to the 1.4 mag bright star Regulus (α Leonis), Leo I (UGC 5470) remained undiscovered for a long time. It was discovered in 1950 along with Leo II by R.G. Harrington and A.G. Wilson in the Palomar Observatory Sky Survey (POSS) photographic plates. [217]

Leo I
Leo I: Star Regulus with galaxy Leo I; Cassegrain 400 mm f/9 + STL 11000M; L: 4x15 min; Observatory Oberes Schlierental, Obwalden; © 2009 Niklaus J. Imfeld, Eduard von Bergen
Leo I
Leo I: Star Regulus with galaxy Leo I; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 140+30+30+30 min LRGBB; Bernese Highlands; © 2015 Radek Chromik

Physical Properties

Leo I is a dwarf elliptical galaxy. It belongs to the Local Group and is a distant companion of our Milky Way. According to measurements published on Simbad, this dwarf galaxy is 0.198 Mpc to 0.26 Mpc (645'800 to 848'000 light-years) away and is receding at a speed of 251 km/s to 290 km/s. The brightness in the V-band is 10.0 mag. [145]

From observations with the Hubble Space Telescope, Gallart et al 1999 conclude that 70-80 percent of star formation took place between seven and one billion years ago. There is little to no evidence for the presence of stars older than 10 billion years. About a billion years ago, star formation abruptly dropped to negligible levels. However, very little star formation appeared to have occurred up to 300 million years ago. [264]

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
DesignationsPGC 29488: Leo I, UGC 5470, MCG 2-26-27, DDO 74, CGCG 64-73, ANON 1005+12
Right Ascension (J2000.0)10h 08m 27.4s
Declination (J2000.0)+12° 18' 27"
Morphological TypeE
Dimensions9.9' x 7.5'
Visual Magnitude11.1 mag
Radial Velocity (HRV)168 km/s
Position Angle80°

Galaxy IC 591

IC 591
IC 591: Section of the Sloan Digitized Sky Survey [147]

The small galaxy IC 591 is much further away. It is of the morphological type SBc. The distance is 41 Mpc (133 million light years) and it is receding at a speed of about 2800 km/s. [145] The small galaxy was discovered on February 8, 1878 by the American astronomer David Peck Todd with a 26 inch reflector. This apparently escaped John LE Dreyer, because in his «Index Catalogue» published in 1895 he names Stephane Javelle as the discoverer who observed IC 591 on March 31, 1892. [277, 314]

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
DesignationsPGC 29435: IC 591, UGC 5458, MCG 2-26-25, CGCG 64-69, ARAK 231, IRAS 10047+1231
Right Ascension (J2000.0)10h 07m 27.6s
Declination (J2000.0)+12° 16' 34"
Morphological TypeS
Dimensions1.0' x .7'
Visual Magnitude14.1 mag
Radial Velocity (HRV)2840 km/s
Position Angle170°

Finder Chart

The dwarf galaxy Leo I is located in the constellation Leo, just 12 arc minutes north of the mag 1.4 star Regulus. It is like the galaxy NGC 404 or the planetary nebula Abell 12 a good test object for the transparency of the sky and the contrast performance of the telescope. The best observation time is January to May.

Leo: Leo I
Chart Leo I
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

762 mm aperture: If Regulus is held outside the 0.52° field of view, a small elliptical-shaped cotton swab is visible north of this at 192x magnification (Tele Vue Ethos 13mm).

— 30" SlipStream-Dobson f/3.3, Hasliberg, 17. 2. 2021, Eduard von Bergen

References

144Catalogue of Principal Galaxies (PGC); Paturel G., Fouque P., Bottinelli L., Gouguenheim L.; Astron. Astrophys. Suppl. Ser. 80, 299 (1989); cdsarc.unistra.fr/viz-bin/cat/VII/119 (2021-02-18)
145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
147Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
217The Messier Catalog (SEDS); messier.seds.org (2021-01-01)
264«Updated Information on the Local Group» Sidney van den Bergh (DAO/HIA/NRC); arXiv:astro-ph/0001040; DOI:10.1086/316548
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
314«Index Catalogue of Nebulæ found in the years 1888 to 1894, with Notes and Corrections to the New General Catalogue» Dreyer, J. L. E.; Memoirs of the Royal Astronomical Society, Vol. 51, p.185; 1895; Bibcode:1895MmRAS..51..185D