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Isis (/ˈsɪs/; minor planet designation: 42 Isis) is a large main-belt asteroid, measuring 100.2 km in diameter. It was discovered by N.R. Pogson on May 23, 1856, at Oxford. It was Pogson's first asteroid discovery.

42 Isis
42Isis (Lightcurve Inversion).png
A three-dimensional model of 42 Isis based on its light curve
Discovered byNorman Robert Pogson
Discovery dateMay 23, 1856
MPC designation(42) Isis
Named after
Isis Pogson
Main belt
Orbital characteristics
Epoch December 31, 2006 (JD 2454100.5)
Aphelion446.706 Gm (2.986 AU)
Perihelion283.890 Gm (1.898 AU)
365.298 Gm (2.442 AU)
1393.737 d (3.82 a)
Physical characteristics
Dimensions102.73 ± 2.73 km[1]
Mass(1.58 ± 0.52) × 1018 kg[1]
Mean density
2.78 ± 0.93 g/cm3[1]
0.171 (geometric)[2]
9.18[3] to 13.50

The asteroid's name was chosen by Manuel John Johnson, director of the Radcliffe Observatory in Oxford. Although Isis is the name of an Egyptian goddess, the name was chosen in homage to Pogson's astronomer daughter, (Elizabeth) Isis Pogson.[4] In addition, the Isis is the stretch of the River Thames that runs through Oxford.[5]

The light curve inversion technique, when applied to photometric observations of this asteroid, show multiple local irregularities. The overall shape displays little elongation, with a ratio between the major and minor axes equal to 1.1. The measured rotation period for this model is 13.59701 hours.[6] The spectrum of 42 Isis reveals the strong presence of the mineral Olivine, a relative rarity in the asteroid belt.[7]


  1. ^ a b c Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science, 73, pp. 98–118, arXiv:1203.4336, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009. See Table 1.
  2. ^ Asteroid Data Sets Archived 2010-01-17 at WebCite
  3. ^ "AstDys (42) Isis Ephemerides". Department of Mathematics, University of Pisa, Italy. Retrieved 2010-06-27.
  4. ^ Bruck, Mary (2009), Women in Early British and Irish Astronomy, Springer, p. 157, ISBN 978-90-481-2472-5.
  5. ^ Lutz D. Schmadel (2011). Dictionary of Minor Planet Names (Addendum to Fifth Edition: 2006–2008 ed.). Springer. ISBN 978-3-642-01966-1.
  6. ^ Torppa, Johanna; et al. (August 2003), "Shapes and rotational properties of thirty asteroids from photometric data", Icarus, 164 (2), pp. 346–383, Bibcode:2003Icar..164..346T, doi:10.1016/S0019-1035(03)00146-5.
  7. ^ Burbine, T. H.; et al. (July 2000), "The Nature of Olivine Asteroids", Meteoritics & Planetary Science, 35, pp. A35, Bibcode:2000M&PSA..35R..35B, doi:10.1111/j.1945-5100.2000.tb01796.x.

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