The M81 group

This group of galaxies is one of the

nearest to our Local Group, being only some

11 million light-years distant, according to 1993 measurements of the

Hubble Space Telescope under the direction of Wendy Freedman of the

Carnegie Institution of Washington by measuring the periods of 32

Cepheid variables in M81 with the pre-repair Wide Field/Planetary Camera

(WFPC I).

The group contains two Messier objects:

and M82

visible in the same field of view at moderate magnification.

Other members include

As radio images such as ours have revealed, NGC 3077 is in considerable

interaction with M81 and M82, plus perhaps some very small galaxies,

as there is a common gaseous envelope.

In our image, M81 is the spiral right and below center,

M82 the not in the upper right center, and NGC 3077 is lower left; at least

two dwarf galaxies appear to show up closely left of M81.

Further, more outlying members of the group include the irregular galaxy

NGC 2366 and the fine Sc spiral NGC 2403,

both lying in the constellation Camelopardalis, IC 2574, “Coddington’s Nebula”,

which is quite irregular but shows some “faint indications of spiral structure”

(Burnham), and the irregulars Holmberg I (UGC 5139) and Holmberg II (UGC 4305).

A full list of the group, as given by R. Brent Tully in his

Nearby Galaxies Catalog, is given in the table below:

Name	RA(h:m)	Dec(d:m)	type	m_v	dim	RV
NGC 2366	7:28.9	+69:13	Ir+	10.91	7.3×3.5	252
NGC 2403	7:36.9	+65:36	Sc	8.39	17.8×11.0	259
M81 dw A	[8:18.7]	[+71:12]				262
Holm. II	8:18.9	+70:43	Ir+	10.75	7.6×6.2	305
UGC 4459	8:34.1	+66:10	Ir+	14.38p	1.7×1.3	144
Holm. I	9:40.5	+71:11	Ir+	12.94	3.5×3.0	287
NGC 2976	9:47.3	+67:55	Scp	10.15	4.9×2.5	175
M81	9:55.6	+69:04	Sb	6.93	25.7×14.1	95
M82	9:55.8	+69:41	Pec	8.41	11.2×4.6	388
NGC 3077	10:03.3	+68:44	E2p	9.85	4.6×3.6	148
M81 dw B	10:05.5	+70:22	Ir+	14.94p	1.2×0.9	479
IC 2574	10:28.4	+68:25	S+	10.56	12.3×5.9	185