The M101 Group

The M101 group contains the giant M101 galaxy and the very famous M51 or whirlpool galaxy. A third bright galaxy - M63 - is probably (although not certainly) also a member of this group.

The M101 Group
M51
M51 and NGC 5195
This is a picture of M51 and its smaller companion galaxy NGC 5195. M51 is a very famous galaxy. It has recently had a close encounter with NGC 5195 and the encounter has had the effect of producing very pronounced spiral arms in M51 as well as spraying billions of stars of NGC 5195 into intergalactic space. It is only in recent years that distance estimates have become good enough to show that these two galaxies are definite members of the M101 group.

The Galaxies of the M101 Group

This is a list of the main galaxies in the M101 group. This group has never been properly studied and so this list only contains the galaxies which are the most probable members. UGC8331, M51, NGC5195, M101, NGC5474, NGC5477, NGC5585 and UGC9405 are all definite members of this group - the other galaxies are less certain.

  1             2        3      4     5      6    7     8     9
Name           Equatorial      Blue  Type  Size Size   RV   Other
               Coordinates     Mag          (')  kly  km/s  Names
               RA       Dec
UGC 8313     13 13.9  +42 13   14.8  SBc    1.6   10   832
UGC 8331     13 15.5  +47 30   14.6  Irr    2.5   20   443  DDO 169
M63          13 15.8  +42 02    9.3  Sb    13.2   95   709  NGC 5055
M51          13 29.9  +47 12    8.9  Sb     9.8   70   640  NGC 5194
NGC 5195     13 30.0  +47 16   10.5  S?     5.6   40   649
UGC 8659     13 40.6  +55 26   16.2  Irr    1.0    5    ?
Holmberg IV  13 54.7  +53 54   13.8  Irr    4.3   30   276  UGC 8837
UGC 8882     13 57.3  +54 06   15.3  E      0.8    5    ?
PGC 49674    13 57.6  +51 58   17.3  Irr    0.6    5    ?   MCG9-23-21
M101         14 03.2  +54 21    8.3  SBc   28.8  210   367  NGC 5457
NGC 5474     14 05.1  +53 40   11.3  Sc     4.8   35   405
NGC 5477     14 05.6  +54 28   14.4  Sm     1.7   10   430
PGC 50911    14 15.2  +57 05   16.5? Irr    0.9   10   432  KKH 87 
NGC 5585     14 19.8  +56 44   11.2  SBc    5.8   40   412
UGC 9405     14 35.4  +57 15   14.5  Irr    1.7   10   310  DDO 194
Column 1: The usual name of the galaxy.
Column 2: The Right Ascension for epoch 2000.
Column 3: The Declination for epoch 2000.
Column 4: The blue apparent magnitude of the galaxy.
Column 5: The galaxy type: E=Elliptical, S0=Lenticular, Sa,Sb,Sc,Sd=Spiral,
          SBa,SBb,SBc,SBd=Barred Spiral, Sm,SBm,Irr=Irregular.
Column 6: The angular diameter of the galaxy (arcminutes).
Column 7: The diameter of the galaxy (thousands of light years).
Column 8: The recessional velocity (km/s) of the galaxy relative to
          the cosmic microwave background.
Column 9: Other names of the galaxy.

References:
Bremnes T, Binggeli B, Prugniel P, (1999), Structure and stellar content of dwarf
        galaxies. III. B and R photometry of dwarf galaxies in the M 101 group
        and the nearby field. Astron Astrophys Supp, 137, 337.
Giuricin G, Marinoni C, Ceriani L, Pisani A, (2000), Nearby optical galaxies:
        selection of the sample and identification of groups. Astrophys J, 543, 178.
Garcia A, (1993), General study of group membership. II. Determination of nearby
        groups. Astron Astrophys Supp, 100, 47.
Fouqué P, Gourgoulhon E, Chamaraux P, Paturel G, (1992), Groups of Galaxies within
        80 Mpc, Astron and Astrophys Supp, 93, 211.
The HyperLeda Database, (2003).

Below - three galaxies in the M101 group. M63 (left) is a bright galaxy, but it may possibly lie behind the M101 group. NGC 5474 (centre) is a disturbed spiral galaxy which has probably had a close encounter with M101 in its recent history. NGC 5585 (right) is a fairly irregular spiral galaxy.

M63 NGC 5474 NGC 5585
M63 NGC 5474 NGC 5585

Shown below is the M101 galaxy. This is another very famous galaxy. It is also a very large spiral galaxy - with a diameter of over 200 thousand light years, it is twice as wide as the Milky Way. This galaxy may be one of the largest galaxies in the entire Virgo supercluster.

M101
M101

Properties of the M101 Group
Equatorial Coordinates RA=14h00m Dec=+50°
Galactic Coordinates l=100° b=+65°
Supergalactic Coordinates L=70° B=+20°
Distance to the centre of the group 25 million light years
Number of large galaxies 7
Alternative names for the group M101/M51 Group
The Virgo Supercluster Back to the Virgo Supercluster page