20 Massalia
Minorplanetyes
Background
  1. D6D6D6
DiscovererA. de Gasparis
Discovery siteNaples Obs.
Discovered19 September 1852
Mpc name(20) Massalia
Alt namesMassilia /mæˈsɪliə/[1]
Pronounced/mæˈseɪliə/[2]
AdjectiveMassalian /mæˈseɪliən/[2]
Named afterMarseille (French city)[3]
Mp categorymain belt[4][5] · Massalia[6]
Epoch23 March 2018 (JD 2458200.5)
Uncertainty0
Observation arc164.08 yr (59,929 d)
Aphelion2.7514 AU
Perihelion2.0662 AU
Time periastron2021-Nov-04
Semimajor2.4088 AU
Eccentricity0.1422
Period3.74 yr (1,366 d)
Mean anomaly12.443°
Mean motion/ day
Inclination0.7087°
Asc node206.11°
Arg peri256.58°
Dimensions160×145×132 km[7]
160×145×130 km[8]
Mean diameter145.50 ± 9.3 km[9]
Mass5.2×1018 kg[10]
5.67×1018 kg[7]
Density3.54 ± 0.85 g/cm3[7]
Rotation8.098 h[11]
Albedo0.210[9]
Magnitude8.3[12] to 12.0
Abs magnitude6.50[5][11]

20 Massalia 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 Latin name of the French city of Marseille, from which the independent discover Jean Chacornac sighted it the following night.[3] It was the first asteroid that was not assigned an iconic symbol by its discoverer.[13]

It came to opposition 179 degrees from the Sun on 21 March 2026.[14]

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.[6][15]: 23 It is by far the largest body in this family. The remaining family members are fragments ejected by a cratering event on Massalia.[16]

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.[5]

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 unfractured 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.[10] The calculation of the mass of Massalia is dependent on the mass of 4 Vesta and perturbation of 44 Nysa.[10]

Light curve analysis indicates that Massalia's pole points towards ecliptic coordinates either (β, λ) = (45°, 10°) or (β, λ) = (45°, 190°) with a 10° uncertainty.[8] This gives an axial tilt of 45° in both cases. The shape reconstruction from light curves has been described as quite spherical with large planar, nonconvex parts of the surface.

In 1988 there was a search for satellites or dust orbiting this asteroid using the UH88 telescope at the Mauna Kea Observatories, but none were found.[17]

In February 2024, water molecules were discovered on 20 Massalia, alongside 7 Iris, marking the first time water molecules were detected on asteroids.[18][19]

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)[3] was the first asteroid that was not assigned an iconic symbol: indeed the circled number 20 was explicitly proposed as the symbol instead.[13]

References

  1. ^ John Craig (1869) The Universal English Dictionary
  2. ^
  3. ^ Schmadel, Lutz D. (2007). "(20) Massalia". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 17. doi:10.1007/978-3-540-29925-7_21. ISBN 978-3-540-00238-3.
  4. ^ "20 Massalia". Minor Planet Center. Retrieved 29 March 2018.
  5. ^ "JPL Small-Body Database Browser: 20 Massalia" (2018-01-24 last obs.). Jet Propulsion Laboratory. Retrieved 29 March 2018.
  6. ^ "Asteroid 20 Massalia". Small Bodies Data Ferret. Retrieved 24 October 2019.
  7. ^ Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Archived from the original on 2 July 2013. Retrieved 11 December 2008.
  8. ^ M. Kaasalainen et al. (2002). "Models of Twenty Asteroids from Photometric Data". Icarus. 159 (2): 369–395. Bibcode:2002Icar..159..369K. doi:10.1006/icar.2002.6907
  9. ^ Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 30 October 2019.
  10. ^ 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
  11. ^ No. 20. Retrieved 29 March 2018.
  12. ^ Donald H. Menzel & Jay M. Pasachoff (1983). A Field Guide to the Stars and Planets. 2nd ed. Boston, MA: Houghton Mifflin. pp. 391. ISBN 978-0-395-34835-2.
  13. ^ Bala, Gavin Jared & Miller, Kirk (18 September 2023). "Unicode request for historical asteroid symbols". unicode.org. Unicode. Retrieved 26 September 2023.
  14. ^ JPL Horizons (Opposition)
  15. ^ Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families". Asteroids IV. pp. 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. ISBN 9780816532131.
  16. ^ D. Vokrouhlický et al. (2006). "Yarkovsky/YORP chronology of asteroid families". Icarus. 182 (1): 118–142. Bibcode:2006Icar..182..118V. doi:10.1016/j.icarus.2005.12.010
  17. ^ 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. Vol. 19, pp. 405–406, Bibcode:1988LPI....19..405G
  18. ^ Arredondo, Anicia; McAdam, Margaret M.; Honniball, Casey I.; Becker, Tracy M.; Emery, Joshua P.; Rivkin, Andrew S.; Takir, Driss; Thomas, Cristina A. (12 February 2024). "Detection of Molecular H2O on Nominally Anhydrous Asteroids". The Planetary Science Journal. 5 (2): 37. Bibcode:2024PSJ.....5...37A. doi:10.3847/PSJ/ad18b8
  19. ^ Gamillo, Elizabeth (14 February 2024). "Water molecules identified on asteroids for the first time". Astronomy. Retrieved 27 March 2024.