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Criteria to classify
a body as a “dwarf planet”
1)
The diameter of
the body should be D >450 km for icy objects and D
>800km for rocky ones. These limits are not precisely determined and
they depend on factors like the composition of the material and the
ambient temperature.
2)
If there is a
direct measurement of the relative roughness with values < 1% and the
shape correspond to a figure of equilibrium, the candidate is accepted
(Case I).
3)
If not, we analyze
the observed lightcurve amplitude (Dm).
()
4)
If
Dm
< 0.15 mag, the
candidate is accepted as a small departure from a sphere or MacLaurin
spheroid with small albedo spots (Case II).
5)
If
Dm
≥ 0.15 mag, the lightcurve (the
intensity square) is fitted to a Fourier series of order two and the
ratio (b)
between the quadratic sums of the coefficients of order 1 and 2 is
computed.
6)
If
b
<0.25, the
lightcurve can be fitted to a triaxial ellipsoid. We then analyze if
this ellipsoid corresponds to the Jacobi family. We compute the range
of possible densities as a function of the assumed aspect angle of the
observed lightcurve.
7)
If there are
solutions with
r
≥1 gr.cm-3,
the candidate is accepted as a Jacobi ellipsoid (Case III).
8)
If all the
solutions correspond to
r
<1 gr.cm-3,
the candidate is not accepted. The size might be overestimated due to
an assumption of a low albedo (pv>>0.1)
(Case IV).
9)
If
b
>0.25, the
candidate is not accepted, the lightcurve departs from an ellipsoidal
figure possibly due to important contributions of albedo spots or
there is an overestimation of the size due to an assumption of a low
albedo (pv>>0.1) (Case V).
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