Basic object information

Name: M 81
Type of object: Galaxy
Magnitude: 6.9
Surface brightness: 12.3 mag/sq arcmin
Size: 24.9'x11.5'
Position angle: 157°

Position (epoch of date)

Right ascension: 9h 55m 50s
Declination: +69° 3' 26"
Constellation: Ursa Major

Local information

Altitude:  33° 44' 38"
Azimuth: 24° 41' 41"

Transit: 20h 50m 17s

Star atlas chart numbers:

Herald-Bobroff Astroatlas, Chart C-13
Millennium Star Atlas, Charts 537-538 (Vol II)
Sky Atlas 2000.0, Chart 2
Uranometria 2000 Chart 23, Vol 1


Saguaro Astronomy Club v7.2 Catalog Data

Saguaro Astronomy Club, August 2000

Names and designations

M 81
NGC 3031

Type of object: Galaxy

Catalog position for epoch J2000.0

Right ascension:	09h 55m 33.5s
Declination:		+69° 03' 59"

Constellation: Ursa Major

Object information

Magnitude: 6.9
Size: 24.9'x11.5'
Position angle: 157°

Object classification: Sb
Description: ! eB,eL,E 156,gsvmbM,BN
Notes: brightest in group;fine spiral

LEDA Catalog Data

Lyon-Meudon Extragalactic Database (LEDA) supplied by the LEDA team at the CRAL-Observatoire de Lyon (France)

Names and designations

PGC 28630
MESS 81
NGC 3031
UGC 5318
MCG 12-10- 10
CGCG 333- 7
IRAS09514+6918
KCPG 218A

Position information

Right ascension (J2000.0):	09h 55m 33.5s
Declination (J2000.0):		+69° 03' 59"
(Coordinates have high accuracy)

Galactic longitude:	142.09°
Galactic latitude:	40.90°

Supergalactic longitude:	40.77°
Supergalactic latitude:	0.59°

Size and shape information

Apparent major isophotal diameter (D25): 22.6'
Mean error in log10 diameter: 0.044
Ratio of major to minor axes (R25): 1.95
Mean error in log10 R25: 0.038
Major axis position angle: 157°
Inclination between line of sight and polar axis: 63.066°
Apparent corrected diameter: 23.6'
Lyon galaxy group membership number: 176

Morphological information

Morphological type: Sb    
Morphological type code: 2.509
Error in morphological type code: 0.591
Luminosity class code: 2.000
Error in luminosity class code: 0.370

Magnitude and colour index information

Total B magnitude: 7.849
Error in B magnitude: 0.100
Mean surface brightness: 21.182 mag/sq arcsec
Error in surface brightness: 0.490 mag/sq arcsec
Total B-V colour index: 0.950
Effective U-B colour index: 0.580
Effective B-V colour index: 1.015
21cm line width at 20% of peak (w20): 441.756 km/sec
Error in w20: 5.416 km/sec
21cm line width at 50% of peak (w50): 421.814 km/sec
Error in w50: 4.595 km/sec
Central velocity dispersion: 168.3 km/sec
Error in log10 velocity dispersion: 0.025
21cm line flux in magnitude: 10.125
Error in 21cm line flux in magnitude: 0.284
Far infrared magnitude: 8.595
Galactic extinction in B mag: 0.322 mag
Extinction in B mag due to inclination: 0.386 mag
21cm self-absorption in magnitude: 0.037 mag
Luminosity index: 0.433
Total apparent corrected B mag: 7.141
Mean surface brightness within isophote 25: 22.913 mag/sq arcsec
Maximum rotational velocity: 221.3 km/sec
Error in log10 rotational velocity: 0.015
Corrected 21cm line flux in magnitude: 10.088
21cm index bt-am21c in magnitude. 2.947

Radial velocity information

Heliocentric RV from radio measurements: -35.3 km/sec
Error in radio measurements: 5.6 km/sec
Heliocentric RV from optical measurements: -59.7 km/sec
Error in optical measurements: 72.1 km/sec
Mean heliocentric RV: -35.4 km/sec
Error in mean measurements: 5.5 km/sec
RV with respect to local group: 124.3 km/sec
RV with respect to GSR: 71.5 km/sec
RV corrected for infall of LG onto Virgo: 200.8 km/sec
RV with respect to the 3K CMB: 50.0 km/sec
Absolute B magnitude: -21.507