Summary for : (476) Hedwig

DynT.TT.BT T.L B T.DDensity (g/cm^3)Δρ/ρDiameter (km)ΔD/DMass (kg)ΔM/MRefAvg.M
MBAPX- | --1.33 ± 0.39   (C)29 %132.1 ± 7.15.3 %1.61e+18 ± 3.90e+1724 %SEVM
MBAPX- | --1.13 ± 0.28   (C)25 %137.4 ± 7.55.5 %1.53e+18 ± 2.81e+1718 %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
(476) Hedwig124.61 ± 4.023.2 % STM2010D64 3.50 1
(476) Hedwig124.02 ± 5.844.7 % NEATM2010D64 1.93 2
(476) Hedwig138.49 ± 0.980.7 % STM2011D722 42.06 3

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 = (132.1 ± 7.05) km   (ΔD/D = 5%, SNR = 18.74) Derived bulk density ρ = (1.33 ± 0.39) g/cm3   (Δρ/ρ = 29%, SNR = 3.4)


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.
D72(2011):Masiero, J.R., Mainzer, A.K., Grav, T., Bauer, J.M., Cutri, R.M., Dailey, J., Eisenhardt, P.R.M., McMillan, R.S., Spahr, T.B., Skrutskie, M.F., Tholen, D., Walker, R.G., Wright, E.L., DeBaun, E., Elsbury, D., Gautier, IV, T., Gomillion, S., Wilkins, A., 2011. Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters. Astrophysical Journal 741, 68.

Mass estimates

DesignationMass / Err (kg)ΔM/MMethodYearRefNχ2Use
(476) Hedwig1.23e+18 ± 5.37e+1744 %Deflec 2014M1210.49 1
(476) Hedwig1.39e+18 ± 3.98e+1729 %OrbFitN 2014M1230.29 2
(476) Hedwig1.92e+18 ± 5.79e+1730 %Deflec 2017M1250.30 3
(476) Hedwig2.30e+18 ± 9.99e+1743 %Ephem 2019M1260.49 4

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).

Deflec : Orbital deflection (close encounter) of one or several test asteroids (classical LSQ). Ephem : Planetary ephemeris solution. OrbFitN : Simultaneous multi-asteroid astrometric orbit solution (similar to 'Ephem').


EVM mass average M = (1.606 ± 0.390) × 1018 kg   (ΔM/M = 24%, SNR = 4.1) Derived bulk density ρ = (1.33 ± 0.39) g/cm3   (Δρ/ρ = 29%, SNR = 3.4)


References
M121(2014):Kretlow, M., 2014. An Astrometric Mass Estimate for 476 Hedwig. The Minor Planet Bulletin (ISSN 1052-8091), Vol. 41, No. 2, pp. 90-91.
M123(2014):Goffin, E., 2014. Astrometric asteroid masses: a simultaneous determination. Astronomy & Astrophysics, Volume 565, id.A56, 8 pp.
M125(2017):Baer, J., Chesley, S.R., 2017. Simultaneous Mass Determination for Gravitationally Coupled Asteroids. The Astronomical Journal, Volume 154, Issue 2, article id. 76, 11 pp.
M126(2019):Fienga, A., et. al, 2019. INPOP19a planetary ephemeris. Notes Scientifiques et Techniques de l'Institut de mécanique céleste,