Summary for : (24) Themis

DynT.TT.BT T.L B T.DDensity (g/cm^3)Δρ/ρDiameter (km)ΔD/DMass (kg)ΔM/MRefAvg.M
MBACBB | CC1.81 ± 0.73   (C)40 %183.8 ± 11.46.2 %5.89e+18 ± 2.12e+1836 %SEVM
MBACBB | CC2.43 ± 0.83   (C)34 %180.0 ± 16.08.9 %7.42e+18 ± 1.60e+1822 %Sw.avg
MBAC1.81 ± 0.67   (C)37 %183.8 ± 11.46.2 %5.89e+18 ± 1.91e+1832 %C?

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)

Object is a Gaia target for mass determination !

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
(24) Themis176.80 ± 2.291.3 % TPM2011D83 9.37 1
(24) Themis202.33 ± 6.053.0 % NEATM2011D72 9.37 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. TPM : Thermophysical Model.



EVM diam. average D = (183.8 ± 11.39) km   (ΔD/D = 6%, SNR = 16.13) Derived bulk density ρ = (1.81 ± 0.73) g/cm3   (Δρ/ρ = 40%, SNR = 2.5)



References
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.
D83(2011):Usui, F., Kuroda, D., Müller, T.G., Hasegawa, S., Ishiguro, M., Ootsubo, T., Ishihara, D., Kataza, H., Takita, S., Oyabu, S., Ueno, M., Matsuhara, H., Onaka, T., 2011. Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey. Publications of the Astronomical Society of Japan 63, 1117–1138.


Mass estimates

DesignationMass / Err (kg)ΔM/MMethodYearRefNχ2Use
(24) Themis5.75e+18 ± 2.51e+1844 %Deflec 1997M120.00 1
(24) Themis1.99e+18 ± 3.98e+18200 %Ephem 2007M6220.96 2
(24) Themis1.13e+19 ± 4.28e+1838 %Deflec 2008M7121.59 3
(24) Themis6.04e+18 ± 6.04e+1710 %Ephem 2009M860.06 4
(24) Themis5.62e+18 ± 3.78e+1867 %Ephem 2010M930.01 5
(24) Themis3.96e+18 ± 2.81e+1871 %Deflec 2011M970.47 6
(24) Themis4.78e+18 ± 1.84e+1838 %Deflec 2011M970.37 7
(24) Themis6.16e+18 ± 1.85e+1830 %Deflec 2011M970.02 8
(24) Themis5.25e+18 ± 2.34e+1845 %Deflec 2011M970.08 9
(24) Themis1.06e+19 ± 4.57e+1843 %Ephem 2011M10021.06 10
(24) Themis1.01e+19 ± 5.97e+176 %OrbFitN 2014M123250.56 11
(24) Themis3.73e+18 ± 1.57e+1842 %Ephem 2019M1261.90 12

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 = (5.895 ± 2.117) × 1018 kg   (ΔM/M = 36%, SNR = 2.8) Derived bulk density ρ = (1.81 ± 0.73) g/cm3   (Δρ/ρ = 40%, SNR = 2.5)



References
M12(1997):Lopez Garcia, A., Medvedev, Y.D., Morano Fernendez, J.A., 1997. Using Close Encounters of Minor Planets for the Improvement of their Masses, in: I. M. Wytrzyszczak, J. H. Lieske, & R. A. Feldman (Ed.), IAU Colloq. 165: Dynamics and Astrometry of Natural and Artificial Celestial Bodies, p. 199.
M62(2007):Aslan, Z., Gumerov, R., Hudkova, L., Ivantsov, A., Khamitov, I., Pinigin, G., 2007. Mass Determination of Small Solar System Bodies with Ground-based Observations, in: O. Demircan, S. O. Selam, & B. Albayrak (Ed.), Solar and Stellar Physics Through Eclipses, pp. 52–58.
M71(2008):Baer, J., Chesley, S.R., 2008. Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris. Celestial Mechanics and Dynamical Astronomy 100, 27–42.
M86(2009):Folkner, W.M., Williams, J.G., Boggs, D.H., 2009. The planetary and lunar ephemeris de 421. IPN Progress Report 42, 1–34.
M93(2010):Fienga, A., Manche, H., Kuchynka, P., Laskar, J., Gastineau, M., 2010. INPOP10a. Scientific Notes.
M97(2011):Zielenbach, W., 2011. Mass Determination Studies of 104 Large Asteroids. Astronomical Journal 142, 120–128.
M100(2011):Fienga, A., Kuchynka, P., Laskar, J., Manche, H., Gastineau, M., 2011. Asteroid mass determinations with INPOP planetary ephemerides. EPSC-DPS Joint Meeting 2011 , 1879.
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,