Sabe que Júpiter tem umas 18 luas, né?
Ops!
Falha nossa.
Quis Dizer todas as quatro luas galileanas(Europa, Io, Ganimedes, calisto). 
Veja que se passaram mais de 280 anos para se achar Almathea e Themisto (o 18º que só foi descoberto em 2.000).
Portanto é comum nos esquecermos das luas não-galileanas e desconhecer a contagem atual.
I Io Galileu (1610)
II Europa Galileu (1610)
III Ganymede Galileu (1610)
IV Callisto Galileu (1610)
V Amalthea E.E. Barnard (1892)
VI Himalia C. Perrine (1904)
VII Elara C. Perrine (1905)
VIII Pasiphae P. Melotte (1908)
IX Sinope S. Nicholson (1914)
X Lysithea S. Nicholson (1938)
XI Carme S. Nicholson (1938)
XII Ananke S. Nicholson (1951)
XIII Leda C. Kowal (1974)
XIV Thebe S/1979 J2 S. Synnott/Voyager 1 (1980)
XV Adrastea S/1979 J1 D. Jewitt, E. Danielson (1979)
XVI Metis S/1979 J3 S. Synnott/Voyager 2 (1980)
XVII Callirrhoe S/1999 J1 J.V. Scotti, T.B. Spahr, R.S. McMillan, J.A. Larsen, J. Montani, A.E. Gleason, T. Gehrels (1999)
XVIII Themisto S/1975 J1 # Sheppard, Jewitt, Fernandez, Magnier (2000)
XIX Megaclite S/2000 J8 Sheppard, Jewitt, Fernandez, Magnier (2000)
XX Taygete S/2000 J9 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXI Chaldene S/2000 J10 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXII Harpalyke S/2000 J5 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXIII Kalyke S/2000 J2 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXIV Iocaste S/2000 J3 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXV Erinome S/2000 J4 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXVI Isonoe S/2000 J6 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXVII Praxidike S/2000 J7 Sheppard, Jewitt, Fernandez, Magnier (2000)
XXVIII Autonoe S/2001 J1 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXIX Thyone S/2001 J2 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXX Hermippe S/2001 J3 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXI Aitne S/2001 J11 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXII Eurydome S/2001 J4 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXIII Euanthe S/2001 J7 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXIV Euporie S/2001 J10 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXV Orthosie S/2001 J9 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXVI Sponde S/2001 J5 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXVII Kale S/2001 J8 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXVIII Pasithee S/2001 J6 S.S. Sheppard, D.C. Jewitt, J. Kleyna (2001)
XXXIX Hegemone S/2003 J8 S.S. Sheppard (2003)
XL Mneme S/2003 J21 S.S. Sheppard, B. Gladman (2003)
XLI Aoede S/2003 J7 S.S. Sheppard (2003)
XLII Thelxinoe S/2003 J22 S.S. Sheppard, B. Gladman (2004)
XLIII Arche S/2002 J1 S.S. Sheppard (2002)
XLIV Kallichore S/2003 J11 S.S. Sheppard (2003)
XLV Helike S/2003 J6 S.S. Sheppard (2003)
XLVI Carpo S/2003 J20 S.S. Sheppard (2003)
XLVII Eukelade S/2003 J1 S.S. Sheppard (2003)
XLVIII Cyllene S/2003 J13 S.S. Sheppard (2003)
(50) S/2000 J11 S.S. Sheppard, D.C. Jewitt, Y. Fernandez, G. Magnier (2000)
(51) S/2003 J2 S.S. Sheppard (2003)
(52) S/2003 J3 S.S. Sheppard (2003)
(53) S/2003 J4 S.S. Sheppard (2003)
(54) S/2003 J5 S.S. Sheppard (2003)
(55) S/2003 J9 S.S. Sheppard (2003)
(56) S/2003 J10 S.S. Sheppard (2003)
(57) S/2003 J14 S.S. Sheppard (2003)
(58) S/2003 J15 S.S. Sheppard (2003)
(59) S/2003 J16 B. Gladman (2003)
(60) S/2003 J17 B. Gladman (2003)
(61) S/2003 J18 B. Gladman (2003)
(62) S/2003 J19 B. Gladman (2003)
(63) S/2003 J23 S.S. Sheppard (2003)