20 Massalia

20 Massalia
Lightcurve-based 3D-model of Massalia
Discovery [1]
Discovered by A. de Gasparis
Discovery site Naples Obs.
Discovery date 19 September 1852
Designations
MPC designation (20) Massalia
Pronunciation /məˈseɪliə/ mə-SAY-lee-ə
Named after
 Marseille (French city)[2]
main belt [1][3] · Massalia [4]
Orbital characteristics [3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc 164.08 yr (59,929 d)
Aphelion 2.7514 AU
Perihelion 2.0662 AU
2.4088 AU
Eccentricity 0.1422
3.74 yr (1,366 d)
12.443°
0° 15m 48.96s / day
Inclination 0.7087°
206.11°
256.58°
Physical characteristics
Dimensions 160×145×132 km[5]
160×145×130 km[6]
Mean diameter
 145.50±9.3 km[7]
Mass 5.2×1018 kg[8]
5.67×1018 kg[5]
Mean density
 3.54±0.85 g/cm3[5]
8.098 h[9]
0.210[7]
Tholen = S [3]
SMASS = S [3]
8.3[10] to 12.0
6.50[3][9]
0.186" to 0.058"

    20 Massalia (/məˈseɪliə/ mə-SAY-lee-ə) is a stony asteroid and the parent body of the Massalia family located in the inner region of the asteroid belt, approximately 145 kilometers (90 miles) in diameter. Discovered by Italian astronomer Annibale de Gasparis on 19 September 1852, it was named for the French city of Marseille, from which the independent discover Jean Chacornac sighted it the following night.[2]

    Classification and orbit

    Massalia is the namesake and the parent body of the Massalia family (404), a very large inner belt asteroid family consisting of stony asteroids with very low inclinations.[4][11]:23 It is by far the largest body in this family. The remaining family members are fragments ejected by a cratering event on Massalia.[12]

    It orbits the Sun in the inner main-belt at a distance of 2.1–2.8 AU once every 3 years and 9 months (1,366 days; semi-major axis of 2.41 AU). Its orbit has an eccentricity of 0.14 and an inclination of 1° with respect to the ecliptic.[3]

    Physical characteristics

    Massalia has an above-average density for S-type asteroids, similar to the density of silicate rocks. As such, it appears to be a solid un-fractured body, a rarity among asteroids of its size. Apart from the few largest bodies over 400 km in diameter, such as 1 Ceres and 4 Vesta, most asteroids appear to have been significantly fractured, or are even rubble piles. In 1998, Bange estimated Massalia to have a mass of 5.2×1018 kg assuming that 4 Vesta has 1.35×10−10 solar mass.[8] The mass of Massalia is dependent on the mass of 4 Vesta and perturbation of 44 Nysa.[8]

    Lightcurve analysis indicates that Massalia's pole points towards either ecliptic coordinates (β, λ) = (45°, 10°) or (β, λ) = (45°, 190°) with a 10° uncertainty.[6] This gives an axial tilt of 45°in both cases. The shape reconstruction from lightcurves has been described as quite spherical with large planar, nonconvex parts of the surface.

    In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty.[13]

    Discovery

    Massalia was discovered on 19 September 1852, by Annibale de Gasparis at Naples Observatory in Italy, and also found independently the next night by Jean Chacornac at Marseilles Observatory, France. It was Chacornac's discovery that was announced first. In the nineteenth century the variant spelling Massilia was often used. Asteroids discovered prior to Massalia were assigned iconic symbols, like the ones traditionally used to designate the planets. However, astronomers had begun to phase out this practice with the discovery of 16 Psyche in March 1852, and 20 Massalia (being the first object in the Solar System with a non-mythological name)[2] was the first asteroid that was not assigned an iconic symbol.

    References

    1. 1 2 "20 Massalia". Minor Planet Center. Retrieved 29 March 2018.
    2. 1 2 3 Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (20) Massalia. Springer Berlin Heidelberg. p. 17. ISBN 978-3-540-00238-3. Retrieved 29 March 2018.
    3. 1 2 3 4 5 6 "JPL Small-Body Database Browser: 20 Massalia" (2018-01-24 last obs.). Jet Propulsion Laboratory. Retrieved 29 March 2018.
    4. 1 2 "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Retrieved 29 March 2018.
    5. 1 2 3 Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Retrieved 2008-12-11.
    6. 1 2 M. Kaasalainen; et al. (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus. 159 (2): 369. Bibcode:2002Icar..159..369K. doi:10.1006/icar.2002.6907.
    7. 1 2 Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. Bibcode:2004PDSS...12.....T. Archived from the original on 3 June 2016. Retrieved 12 November 2017.
    8. 1 2 3 J. Bange (1998). "An estimation of the mass of asteroid 20-Massalia derived from the HIPPARCOS minor planets data". Astronomy & Astrophysics. 340: L1. Bibcode:1998A&A...340L...1B.
    9. 1 2 "LCDB Data for (20) Massalia". Asteroid Lightcurve Database (LCDB). Retrieved 29 March 2018.
    10. ↑ Donald H. Menzel & Jay M. Pasachoff (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston, MA: Houghton Mifflin. p. 391. ISBN 0-395-34835-8.
    11. ↑ Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families" (PDF). Asteroids IV: 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. Retrieved 29 March 2018.
    12. ↑ D. Vokrouhlický; et al. (2006). "Yarkovsky/YORP chronology of asteroid families". Icarus. 182: 118. Bibcode:2006Icar..182..118V. doi:10.1016/j.icarus.2005.12.010.
    13. ↑ Gradie, J.; Flynn, L. (March 1988), "A Search for Satellites and Dust Belts Around Asteroids: Negative Results", Abstracts of the Lunar and Planetary Science Conference, 19, pp. 405–406, Bibcode:1988LPI....19..405G

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