Galaxies Messier 91 & NGC 4571

Messier 91
Messier 91: Galaxy M91 in Coma Berenices; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 220+90+90+90 min LRGB; Bernese Highlands; © 2016 Radek Chromik


Charles Messier discovered the galaxy M 91 on 18 March 1781 and wrote: «Nebula without a star, in Virgo, above the previous number 90: The light is even weaker than the previous one [M 90]. Note: The constellation Virgo, especially the northern part, is one of the constellations that contains the most nebulae. This catalog contains thirteen of them that have been determined. The following numbers: 49, 58, 59, 60, 61, 84, 85, 86, 87, 88, 89, 90 and 91. All these nebulae appear without a star and you can only see them in a clear sky if they have the meridian happen. Most of these nebulae were found by M. Méchain.» [281]

At the coordinates that Messier stated at the time, there is no nebula that fits the description and so M 91 was considered lost for a long time. It was not until 1969 that an amateur astronomer discovered that Messier probably measured the position of M 91 using M 89, while he believed it was M 58 and that the position was therefore incorrectly entered. If you reproduce Messier's measurement error, you get to the position of NGC 4548 with an accuracy of 0.1 minutes in right ascension and 1' in declination. M 91 must therefore be NGC 4548. [217]

Physical Properties

M 91 is a beautiful bar-spiral galaxy of the morphological type SB_a and has a LINER-type active core. Measured distances range from 16.2 Mpc to 19 Mpc. [145]

Revised+Historic NGC/IC, Version 22/9, © Dr. Wolfgang Steinicke [277]
DesignationNGC 4548
TypeGx (SBb)
Right Ascension12h 35m 26.4s
Declination+14° 29' 47"
Diameter5.2 × 4.2 arcmin
Photographic (blue) magnitude11.0 mag
Visual magnitude10.2 mag
Surface brightness13.4 mag·arcmin-2
Position angle150°
Distance derived from z6.85 Mpc
Metric Distance16.200 Mpc
Dreyer DescriptionB, L, lE, lbM
Identification, RemarksM 91, UGC 7753, MCG 3-32-75, IRAS 12328+1446, CGCG 99-96, VCC 1615
NGC 4571
NGC 4571: Section of the Sloan Digitized Sky Survey [147]

Further Galaxies in that Area

The spiral galaxy NGC 4571 is located just under half a degree from M 91 and directly next to the 8.9 mag bright star SAO 100177. It was discovered by Wilhelm Herschel on 14 January 1787 and in 1888 by Dreyer under the number 4571 in his «New General Catalog of Nebulae and Cluster of Stars». On 23 November 1900, the German astronomer Arnold Schwassmann looked at the place in the sky. He apparently misinterpreted the 15th mag star west of the galaxy as NGC 4571 and believed it was a new discovery, which is why the same galaxy later received a second entry in the «Index Catalogue» as IC 3588. [196]

NGC 4571 is a spiral galaxy of the morphological type SA (r) d and is located about 16.5 Mpc to 19.4 Mpc from Earth.

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
NameRA [hms]Dec [dms]mTypeDim [']Btot [mag]HRV [km/s]PA [°]
PGC 4197812 35 44.3+14 24 47S R.7 x .315.6
PGC 42100, NGC 4571, IC 358812 36 56.6+14 13 03S3.7 x 3.411.934255

Finder Chart

The two galaxies are located in the constellation Coma Berenices. The best observation time is January to July.

Chart Galaxies Messier 91 & NGC 4571
Galaxies Messier 91 & NGC 4571 in constellation Coma Berenices. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)


144Catalogue of Principal Galaxies (PGC); Paturel G., Fouque P., Bottinelli L., Gouguenheim L.; Astron. Astrophys. Suppl. Ser. 80, 299 (1989); (2021-02-18)
145SIMBAD astronomical database;
147Aladin Lite; (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
196Celestial Atlas by Curtney Seligman; (2020-12-28)
217The Messier Catalog (SEDS); (2021-01-01)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; (2021-02-17)
281«Catalogue Nébuleuses et des Amas D'Étoiles» Observées à Paris, par M. Messier, à l'Observatoire de la Marine, hôtel de Clugni, rue des Mathurins. «Connoissance des temps ou connoissance des mouvements célestes, pour l'année bissextile 1784 » Page 227; (2021-02-21)