View source for 20 Massalia

{{Short description|Main-belt Massalian asteroid}}
{{Use dmy dates|date=September 2019}}
{{Infobox planet
 | minorplanet     = yes
 | name            = 20 Massalia
 | background      = #D6D6D6
 | image           = A112.M119.shape.png
 | image_scale      =
 | caption         = [[Lightcurve]]-based 3D-model of Massalia
 | discovery_ref   = <ref name="MPC-object" />
 | discoverer      = [[Annibale de Gasparis|A. de Gasparis]]
 | discovery_site  = [[Astronomical Observatory of Capodimonte|Naples Obs.]]
 | discovered      = 19 September 1852
 | mpc_name        = (20) Massalia
 | alt_names       = Massilia {{IPAc-en|m|æ|ˈ|s|ɪ|l|i|ə}}<ref>John Craig (1869) ''The Universal English Dictionary''</ref>
 | pronounced      = {{IPAc-en|m|æ|ˈ|s|eɪ|l|i|ə}}<ref name=OED/>
 | adjective       = Massalian {{IPAc-en|m|æ|ˈ|s|eɪ|l|i|ə|n}}<ref name=OED>{{OED|Messalian, Massalian}}</ref>
 | named_after     = [[Marseille]] {{small|(French city)}}<ref name="springer" />
 | mp_category     = {{nowrap|[[main belt]]<ref name="MPC-object" /><ref name="jpldata" />{{·}}[[Massalia family|Massalia]]<ref name="Ferret" />}}
 | orbit_ref       = <ref name="jpldata" />
 | epoch           = 23 March 2018 ([[Julian day|JD]] 2458200.5)
 | uncertainty     = 0
 | observation_arc = 164.08 [[Julian year (astronomy)|yr]] (59,929 d)
 | aphelion        = 2.7514 [[Astronomical unit|AU]]
 | perihelion      = 2.0662 AU
 | time_periastron  = 2021-Nov-04
 | semimajor       = 2.4088 AU
 | eccentricity    = 0.1422
 | period          = 3.74 yr (1,366 d)
 | mean_anomaly    = 12.443[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.2636|sup=ms}} / day
 | inclination     = 0.7087°
 | asc_node        = 206.11°
 | arg_peri        = 256.58°
 | dimensions      = 160×145×132 km<ref name=Baer /><br />160×145×130 km<ref name="Kaasalainen02" />
 | mean_diameter   = {{val|145.50|9.3|u=km}}<ref name="SIMPS" />
 | mass            = {{val|5.2|e=18|u=kg}}<ref name="Bange98" /><br />{{val|5.67|e=18|u=kg}}<ref name=Baer/>
 | density         = {{val|3.54|0.85|u=g/cm3}}<ref name=Baer/>
 | rotation        = {{val|8.098|ul=h}}<ref name="lcdb" />
 | spectral_type   = [[Tholen classification|Tholen]] {{=}} [[S-type asteroid|S]]<ref name="jpldata" /><br />[[SMASS classification|SMASS]] {{=}} [[S-type asteroid|S]]<ref name="jpldata" />
 | albedo          = 0.210<ref name="SIMPS" />
 | magnitude       = 8.3<ref name="Pasachoff1983" /> to 12.0
 | abs_magnitude   = 6.50<ref name="jpldata" /><ref name="lcdb" />
 | angular_size    = 0.186" <!-- Horizons 2017-Dec-06 --> to 0.058"
}}

'''Massalia''' ([[minor planet designation]]: '''20 Massalia''') is a stony [[asteroid]] and the parent body of the [[Massalia family]] located in the inner region of the [[asteroid belt]], approximately {{convert|145|km|mi|abbr=off|sp=us}} 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.<ref name="springer" /> It was the first asteroid that was not assigned an iconic symbol by its discoverer.<ref name=astunicode>{{cite web |url=https://www.unicode.org/L2/L2023/23207-historical-asteroids.pdf |title=Unicode request for historical asteroid symbols |last1=Bala |first1=Gavin Jared |last2=Miller |first2=Kirk |date=18 September 2023 |website=unicode.org |publisher=Unicode |access-date=26 September 2023 |quote=}}</ref>

It came to [[Opposition (astronomy)|opposition]] 179 degrees from the Sun on 16 June 2023,<ref name="opposition">[https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%2720%27&START_TIME=%272023-06-01%27&STOP_TIME=%272023-06-25%27&STEP_SIZE=%276%20hour%27&QUANTITIES=%279,19,20,23,29,39%27 JPL Horizons (Opposition)]</ref> and came to [[aphelion]] (farthest distance from the Sun) on 17 September 2023.{{needs update|date=March 2024}}

== Classification and orbit ==
''Massalia'' is the namesake and the [[parent body]] of the [[Massalia family]] ({{small|[[FIN tbl#404|404]]}}), a very large inner belt [[asteroid family]] consisting of [[S-type asteroid|stony asteroids]] with very low inclinations.<ref name="Ferret" /><ref name="Nesvorny-2014" />{{rp|23}} It is by far the largest body in this family. The remaining family members are fragments ejected by a cratering event on Massalia.<ref name="Vokrouhlicky06" />

It orbits the Sun in the [[Kirkwood gap|inner]] main-belt at a distance of 2.1–2.8&nbsp;[[Astronomical unit|AU]] once every 3 years and 9 months (1,366 days; [[semi-major axis]] of 2.41&nbsp;AU). Its orbit has an [[orbital eccentricity|eccentricity]] of 0.14 and an [[orbital inclination|inclination]] of 1[[Degree (angle)|°]] with respect to the [[ecliptic]].<ref name="jpldata" />

== 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&nbsp;km in diameter, such as [[1 Ceres]] and [[4 Vesta]], most asteroids appear to have been significantly fractured, or are even [[rubble pile]]s. In 1998, Bange estimated Massalia to have a mass of 5.2{{e|18}} kg assuming that 4 Vesta has 1.35{{e|-10}} [[sun|solar mass]].<ref name="Bange98"/> The calculation of the mass of Massalia is dependent on the mass of 4 Vesta and [[Perturbation (astronomy)|perturbation]] of [[44 Nysa]].<ref name="Bange98"/>

[[Light curve]] analysis indicates that Massalia's pole points towards [[ecliptic coordinate system|ecliptic coordinates]] either (β, λ) = (45°, 10°) or (β, λ) = (45°, 190°) with a 10° uncertainty.<ref name="Kaasalainen02" /> 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.<ref name="Gradie1988"/>

In February 2024, water molecules were discovered on 20 Massalia, alongside [[7 Iris]], marking the first time water molecules were detected on asteroids.<ref>{{cite journal|last1=Arredondo|first1=Anicia|last2=McAdam|first2=Margaret M.|last3=Honniball|first3=Casey I.|last4=Becker|first4=Tracy M.|last5=Emery|first5=Joshua P.|last6=Rivkin|first6=Andrew S.|last7=Takir|first7=Driss|last8=Thomas|first8=Cristina A.|date=12 February 2024|title=Detection of Molecular H<sub>2</sub>O on Nominally Anhydrous Asteroids|journal=The Planetary Science Journal|volume=5|issue=2|page=37|doi=10.3847/PSJ/ad18b8|doi-access=free |bibcode=2024PSJ.....5...37A }}</ref><ref>{{cite news|last=Gamillo|first=Elizabeth|title=Water molecules identified on asteroids for the first time|url=https://www.astronomy.com/science/water-molecules-identified-on-asteroids-for-the-first-time/|website=Astronomy|date=14 February 2024|accessdate=27 March 2024}}</ref>

== 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 [[Asteroid#Symbols|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)<ref name="springer"/> was the first asteroid that was not assigned an iconic symbol.

==References==
{{Reflist|refs=

<ref name="jpldata">{{cite web
  |type       = 2018-01-24 last obs.
  |title      = JPL Small-Body Database Browser: 20 Massalia
  |url        = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000020
  |publisher  = [[Jet Propulsion Laboratory]]
  |accessdate = 29 March 2018}}</ref>

<ref name="MPC-object">{{cite web
  |title      = 20 Massalia
  |work       = [[Minor Planet Center]]
  |url        = https://www.minorplanetcenter.net/db_search/show_object?object_id=20
  |accessdate = 29 March 2018}}</ref>

<ref name=Baer>{{cite web
  |date=2008
  |title=Recent Asteroid Mass Determinations
  |publisher=Personal Website
  |author=Jim Baer
  |url=http://home.earthlink.net/~jimbaer1/astmass.txt
  |accessdate=11 December 2008
  |archive-url=https://web.archive.org/web/20130702212735/http://home.earthlink.net/~jimbaer1/astmass.txt
  |archive-date=2 July 2013
  |url-status=dead}}</ref>

<ref name="SIMPS">{{cite journal
  |first1     = E. F. |last1 = Tedesco
  |first2     = P. V. |last2 = Noah
  |first3     = M. |last3 = Noah
  |first4     = S. D. |last4 = Price
  |date       = October 2004
  |title      = IRAS Minor Planet Survey V6.0
  |url        = https://sbnarchive.psi.edu/pds3/iras/IRAS_A_FPA_3_RDR_IMPS_V6_0/data/diamalb.tab
  |journal    = NASA Planetary Data System
  |volume     = 12
  |pages      = IRAS-A-FPA-3-RDR-IMPS-V6.0
  |bibcode    = 2004PDSS...12.....T
  |accessdate = 30 October 2019}}</ref>

<ref name="Kaasalainen02">{{cite journal | author= M. Kaasalainen| title= Models of Twenty Asteroids from Photometric Data| journal= Icarus| date= 2002| volume= 159| pages= 369–395| url= http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf | doi= 10.1006/icar.2002.6907| bibcode=2002Icar..159..369K | issue= 2|display-authors=etal}}</ref>

<ref name="Bange98">{{cite journal | author= J. Bange| title= An estimation of the mass of asteroid 20-Massalia derived from the HIPPARCOS minor planets data| journal= Astronomy & Astrophysics| date= 1998| volume= 340| pages= L1| url= http://articles.adsabs.harvard.edu//full/seri/A%2BA../0340//L000001.000.html|bibcode = 1998A&A...340L...1B }}</ref>

<ref name="lcdb">{{cite web
  |title      = LCDB Data for (20) Massalia
  |publisher  = Asteroid Lightcurve Database (LCDB)
  |url        = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=20%7CMassalia
  |accessdate = 29 March 2018}}</ref>

<ref name="Pasachoff1983">{{cite book | author=Donald H. Menzel | author2=Jay M. Pasachoff | name-list-style=amp | date=1983 | title=A Field Guide to the Stars and Planets | edition=2nd | publisher=[[Houghton Mifflin]] | pages=[https://archive.org/details/fieldguidetostar00menz_0/page/391 391] | location=Boston, MA | isbn=978-0-395-34835-2 | url-access=registration | url=https://archive.org/details/fieldguidetostar00menz_0 }}</ref>

<ref name="springer">{{cite book
  |last       = Schmadel | first = Lutz D.
  |title = Dictionary of Minor Planet Names |publisher  = Springer Berlin Heidelberg
  |page       = 17
  |date       = 2007
  |isbn       = 978-3-540-00238-3
  |doi       = 10.1007/978-3-540-29925-7_21 |chapter       = (20) Massalia }}</ref>

<ref name="Vokrouhlicky06">{{cite journal | author= D. Vokrouhlický| title= Yarkovsky/YORP chronology of asteroid families| journal= Icarus| date= 2006| volume= 182| issue= 1| pages= 118–142 | doi= 10.1016/j.icarus.2005.12.010| bibcode=2006Icar..182..118V|display-authors=etal}}</ref>

<ref name="Gradie1988">{{Citation
 | last1     = Gradie
 | first1    = J.
 | last2     = Flynn
 | first2    = L.
 | title     = A Search for Satellites and Dust Belts Around Asteroids: Negative Results
 | work      = Abstracts of the Lunar and Planetary Science Conference
 | volume    = 19
 | pages     = 405–406
 |date=March 1988
 | bibcode   = 1988LPI....19..405G}}</ref>

<ref name="Ferret">{{cite web
  |title      = Asteroid 20 Massalia
  |work       = Small Bodies Data Ferret
  |url        = https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=20+Massalia
  |accessdate = 24 October 2019}}</ref>

<ref name="Nesvorny-2014">{{Cite book
  |first1     = D. |last1 = Nesvorný
  |first2     = M. |last2 = Broz
  |first3     = V. |last3 = Carruba
  |date       = December 2014
  |chapter      = Identification and Dynamical Properties of Asteroid Families
  |title    = Asteroids IV
  |pages      = 297–321
  |bibcode    = 2015aste.book..297N
  |doi        = 10.2458/azu_uapress_9780816532131-ch016
  |arxiv      = 1502.01628
  |isbn       = 9780816532131}}</ref>

}} <!-- end of reflist -->

== External links ==
* {{cite journal |last1=Kaasalainen |first1=M. |last2=Torppa |first2=J. |last3=Piironen |first3=J. |title=Models of Twenty Asteroids from Photometric Data |journal=Icarus |date=October 2002 |volume=159 |issue=2 |pages=369–395 |doi=10.1006/icar.2002.6907 |bibcode=2002Icar..159..369K |url=http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf |archive-url=https://web.archive.org/web/20090318132318/http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf |archive-date=2009-03-18  |access-date=8 April 2022}}
* [https://web.archive.org/web/20160304051756/http://scully.cfa.harvard.edu/cgi-bin/returnprepeph.cgi?d=b2011&o=00020 Elements and Ephemeris for (20) Massalia] from the Minor Planet Center
* {{AstDys|20}}
* {{JPL small body}}

{{Minor planets navigator |19 Fortuna |number=20 |21 Lutetia}}
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{{DEFAULTSORT:000020}}
[[Category:Massalia asteroids]]
[[Category:Discoveries by Annibale de Gasparis|Massalia]]
[[Category:Named minor planets|Massalia]]
[[Category:S-type asteroids (Tholen)]]
[[Category:S-type asteroids (SMASS)]]
[[Category:Astronomical objects discovered in 1852|18520919]]