Spectroscopie : M51, PGC58046
M51 :
[NII] = 6593A ; repos : 6583.39A z = 0.00146
Ha = 6573A ; repos : 6562.801A z = 0.001554
[NII] = 6558.5A ; repos : 6548.05A z = 0.001596
[OIII] = 5012.5A ; repos : 5006.84A z = 0.00113
z moyen = 0.001435
Vr = 0.001435 x c
Vr = 430.2 km/s
Vr Hel = 443.1 km/s (Vhel = +12.9 km/s)
V gal = 530.66 km/s
Distance M51 :
530.66/70 = 7.58Mpc
Image : 17.5 cm = 19.3' ; 7.5 cm = 8.27'
a) 8.27' = 0.13784°
b) 180° = π rad ; 0.13784° = 2.4 x 10^-3
Taille de M51 :
T = (7.58 x 3.26 x 10^6) x (2.4 x 10^-3)
T = 59 305 AL
PGC58046 :
Ha = 6793A ; repos : 6562.801A z = 0.035
Vr = 0.035 x c
Vr = 14 492.73 km/s
V hel = 10 508.13 km/s (V hel : +15.4 km/s)
V gal = 10 662.56 km/s
Distance PGC58046 :
10 662.56 / 70 = 150.11 Mpc
Image : 18.65 cm = 20.6' 0.5cm = 0.552'
a) 0.552' = 9.2 x 10^-3°
b) 180° = π rad ; 9.2 x 10^-3 = 1.605 x 10^-4 rad
Taille PGC58046 :
T = (150.11 x 3.26 x 10^6) x (1.605 x 10^-4)
T = 78 542 AL
Conclusion :
M51 : taille = 8.27' distance = 7.58Mpc
PGC 58046 : taille = 0.552' distance = 150.11Mpc
PGC58046 est 15 fois plus petite que M51, mais on remarque qu'elle est 19 fois plus loin...