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
which form an appealing interacting pair
visible in the same field of view at moderate magnification.
Other members include
NGC 3077 and
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 |
Key: Name: Some catalog number or name; RA/Dec: Position 2000.0;
type: Hubble type; m_v: apparent visual magnitude; dim: dimension in
arc minutes; RV: radial velocity
(all data from the Sky Catalog 2000 when available).
Last Modification: 18 Apr 1998, 21:00 MEST