Summary for : (54) Alexandra

DynT.TT.BT T.L B T.DDensity (g/cm^3)Δρ/ρDiameter (km)ΔD/DMass (kg)ΔM/MRefAvg.M
MBACC- | -Cgh2.58 ± 1.88   (D)73 %149.2 ± 12.28.2 %4.49e+18 ± 3.08e+1869 %SEVM
MBACC- | -Cgh2.36 ± 1.36   (D)58 %150.6 ± 8.75.8 %4.22e+18 ± 2.32e+1855 %Sw.avg
MBACgh3.50 ± 2.11   (D)60 %149.7 ± 9.96.6 %6.16e+18 ± 3.50e+1857 %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
(54) Alexandra165.75 ± 3.402.1 % STM2004D932 23.80 1
(54) Alexandra177.42 ± 4.562.6 % STM2010D642 38.40 2
(54) Alexandra177.68 ± 7.554.2 % NEATM2010D642 14.27 3
(54) Alexandra146.99 ± 2.311.6 % Occ2011D95 0.88 4
(54) Alexandra135.00 ± 20.0014.8 % MDM:LO2011D78 0.50 5
(54) Alexandra142.00 ± 9.006.3 % MDM:LO2011D78 0.63 6
(54) Alexandra144.46 ± 1.791.2 % STM2011D83 6.90 7
(54) Alexandra142.00 ± 14.7610.4 % NEATM2011D72 0.24 8
(54) Alexandra143.00 ± 5.003.5 % ADAM2017D100 1.52 9

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).

ADAM : All-Data Asteroid Modeling. MDM:LO : Multi-Data Modeling: Lightcurves + Occultations. NEATM : Near-Earth Asteroid Thermal Model. Occ : Stellar occultation. STM : Standard Thermal Model.


EVM diam. average D = (149.2 ± 12.24) km   (ΔD/D = 8%, SNR = 12.19) Derived bulk density ρ = (2.58 ± 1.88) g/cm3   (Δρ/ρ = 73%, SNR = 1.4)


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.
D78(2011):Ďurech, J., Kaasalainen, M., Herald, D., Dunham, D., Timerson, B., Hanuš, J., Frappa, E., Talbot, J., Hayamizu, T., Warner, B.D., Pilcher, F., Galád, A., 2011. Combining asteroid models derived by lightcurve inversion with asteroidal occultation silhouettes. Icarus 214, 652–670.
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.
D93(2004):Tedesco, E.F., Noah, P.V., Noah, M.C., Price, S.D., 2004. IRAS Minor Planet Survey. NASA Planetary Data System. IRAS-A-FPA-3-RDR-IMPS-V6.0.
D95(2011):Dunham, D.W., Herald, D., Frappa, E., Hayamizu, T., Talbot, J., Timerson, B., 2011. Asteroid Occultations. NASA Planetary Data System. EAR-A-3-RDR-OCCULTATIONS-V9.0.
D100(2017):Hanuš, J., Viikinkoski, M., Marchis, F., et al., 2017. Volumes and bulk densities of forty asteroids from ADAM shape modeling. Astronomy and Astrophysics 601, A114 (2017). DOI: 10.1051/0004-6361/201629956

Mass estimates

DesignationMass / Err (kg)ΔM/MMethodYearRefNχ2Use
(54) Alexandra4.45e+18 ± 2.21e+1850 %Ephem 2010M930.00 1
(54) Alexandra1.08e+19 ± 6.11e+1857 %Deflec 2011M971.07 2
(54) Alexandra1.74e+18 ± 3.19e+18183 %Deflec 2011M970.74 3
(54) Alexandra2.94e+18 ± 3.15e+18107 %Deflec 2011M970.24 4
(54) Alexandra6.44e+18 ± 6.95e+18108 %Deflec 2011M970.08 5
(54) Alexandra1.03e+19 ± 1.74e+1817 %Ephem 2011M100211.16 6
(54) Alexandra2.50e+18 ± 9.51e+1738 %Ephem 2019M1264.37 7

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.


EVM mass average M = (4.487 ± 3.082) × 1018 kg   (ΔM/M = 69%, SNR = 1.5) Derived bulk density ρ = (2.58 ± 1.88) g/cm3   (Δρ/ρ = 73%, SNR = 1.4)


References
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.
M126(2019):Fienga, A., et. al, 2019. INPOP19a planetary ephemeris. Notes Scientifiques et Techniques de l'Institut de mécanique céleste,