Summary for : (426) Hippo

DynT.TT.BT T.L B T.DDensity (g/cm^3)Δρ/ρDiameter (km)ΔD/DMass (kg)ΔM/MRefAvg.M
MBAF-X | X-2.22 ± 0.88   (C)39 %117.5 ± 12.010.2 %1.88e+18 ± 4.69e+1725 %SEVM
MBAF-X | X-2.39 ± 0.89   (C)37 %115.6 ± 12.811.1 %1.93e+18 ± 3.32e+1717 %Sw.avg

Average asteroid densities (g/cm^3):
C = 1.3 ± 0.6, B = 2.4 ± 0.5, S = 2.7 ± 0.5, M = 3.5 ± 1.0, P = 2.8 ± 1.6, X = 1.9 ± 0.8, Xc = 4.9 ± 0.9, Xk = 4.2 ± 0.7 (Ref)

Additional resources:
3D Model | JPL New Horizons | Minor Planet Center | Wikipedia (these auto-generated links might not work)

Note: The density estimates have been ranked from (A) to (E), corresponding to the relative error: (B) less than 20%, (C) between 20 and 50%, (D) between 50 and 100%, and (E) more than 100%. (A) stands for (presumably) reliable estimates (accuracy better than 20%), based on more than 5 mass estimates and 5 diameter estimates, or a spacecraft encounter. Apparently unrealistic densities (ρ > 8) are tagged with (X).

EVM: average by using the Expected Value Method (Ref). w.avg: weighted average (with w = 1/err^2).

T.T: Tholen Tax Class. T.B: Bus & Binzel Tax Class. T T.L: S3OS2 Lazarro (Tholen) Tax Class. T.L B: S3OS2 Lazarro (Bus & Binzel) Tax Class. T.D: DeMeo Tax Class.

Ref: S = SiMDA, C = Carry (2012)

Diameter estimates

DesignationDiameter / Err (km)ΔD/DMethodYearRefNχ2Use
(426) Hippo107.33 ± 4.414.1 % STM2010D64 5.32 1
(426) Hippo131.67 ± 6.144.7 % NEATM2010D64 5.32 2

plot, average diameter and derived density

All

Notes (N):
1: This estimate is discarded for the average diameter (and derived density) calculation in Carry (2012).
2: This estimate is discarded for the average diameter (and derived density) calculation in SiMDA (catalog).

NEATM : Near-Earth Asteroid Thermal Model. STM : Standard Thermal Model.


EVM diam. average D = (117.5 ± 12.00) km   (ΔD/D = 10%, SNR = 9.79) Derived bulk density ρ = (2.22 ± 0.88) g/cm3   (Δρ/ρ = 39%, SNR = 2.5)


References
D64(2010):Ryan, E.L., Woodward, C.E., 2010. Rectified Asteroid Albedos and Diameters from IRAS and MSX Photometry Catalogs. Astronomical Journal 140, 933–943.

Mass estimates

DesignationMass / Err (kg)ΔM/MMethodYearRefNχ2Use
(426) Hippo2.19e+18 ± 5.97e+1727 %OrbFitN 2014M1230.26 1
(426) Hippo1.54e+18 ± 7.38e+1748 %Ephem 2019M1260.22 2

plot, average mass and derived density

All

Notes (N):
1: This estimate is discarded for the average mass (and derived density) calculation in Carry (2012).
2: This estimate is discarded for the average mass (and derived density) calculation in SiMDA (catalog).
3: This estimate is an average of individual solutions listed before under the same reference (e.g. M125).

Ephem : Planetary ephemeris solution. OrbFitN : Simultaneous multi-asteroid astrometric orbit solution (similar to 'Ephem').


EVM mass average M = (1.883 ± 0.469) × 1018 kg   (ΔM/M = 25%, SNR = 4.0) Derived bulk density ρ = (2.22 ± 0.88) g/cm3   (Δρ/ρ = 39%, SNR = 2.5)


References
M123(2014):Goffin, E., 2014. Astrometric asteroid masses: a simultaneous determination. Astronomy & Astrophysics, Volume 565, id.A56, 8 pp.
M126(2019):Fienga, A., et. al, 2019. INPOP19a planetary ephemeris. Notes Scientifiques et Techniques de l'Institut de mécanique céleste,