704 Interamnia

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704 Interamnia
SPHERE image of Interamnia.jpg
VLT-SPHERE image of Interamnia
Discovered byVincenzo Cerulli
Discovery date2 October 1910
MPC designation(704) Interamnia
Pronunciation/ɪntərˈæmniə/ in-tər-AM-nee-ə
Named after
1910 KU; 1952 MW
Main belt
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc102.38 yr (37395 d)
Aphelion3.5293 AU (527.98 Gm)
Perihelion2.5857 AU (386.82 Gm)
3.0575 AU (457.40 Gm)
5.35 yr (1952.8 d)
16.92 km/s
0° 11m 3.66s / day
Physical characteristics
Dimensions362 × 348 × 310 ± 8 km[2]
Mean diameter
332±6 km (volume equivalent)[2]
Mass(3.79±1.28)×1019 kg[2]
Mean density
1.98±0.68 g/cm3[2]
8.712336 h[2]
9.9 to 13.0[3]

704 Interamnia is a large F-type asteroid, with an estimated diameter of 350 kilometres. Its mean distance from the Sun is 3.067 (AU). It was discovered on 2 October 1910 by Vincenzo Cerulli, and named after the Latin name for Teramo, Italy, where Cerulli worked. It is probably the fifth-most-massive asteroid after Ceres, Vesta, Pallas, and Hygiea, with a mass estimated to be 1.2% of the mass of the entire asteroid belt.[4] Observations by the Very Large Telescope's SPHERE imager in 2017–2019 have suggested that Interamnia may be in or near hydrostatic equilibrium and thus represents a transitional body between small solar system bodies and dwarf planets.[2]


Observations of 704 Interamnia carried out at the Observatory of Teramo (founded by the discoverer of the asteroid, Vincenzo Cerulli) for the 101st anniversary since its discovery. The animation shows Interamnia's path over three hours.
One of the first photographic plates of 704 Interamnia. The image was taken in Oct. 1910; the path of the asteroid is shown in the zoom.

Although Interamnia is the largest asteroid after the "big four", it is a very little-studied body. It is easily the largest of the F-type asteroids, but until 2017-2019 there existed very few details of its internal composition or shape, and no light curve analysis has yet been done to determine the ecliptic coordinates of Interamnia's poles (and hence its axial tilt). Studies by the Very Large Telescope give an average diameter of about 332 km and found an ellipsoidal shape for Interamnia, similar to 4 Vesta; the resulting density calculation (1.98 ± 0.68 g · cm^3) is not precise enough to definitely infer Interamnia's composition, but the presence of hydrated materials at the surface and its overall spectral similarities to Ceres suggest that it is likely an icy body. The absence of an affiliated asteroid family implies that Interamnia has not suffered a giant impact within the past 3 billion years[5], in contrast to 4 Vesta and 10 Hygeia.[6][7]

Its very dark surface and relatively large distance from the Sun means Interamnia can never be seen with 10x50 binoculars. At most oppositions its magnitude is around +11.0, which is less than the minimum brightness of Vesta, Ceres or Pallas. Even at a perihelic opposition its magnitude is only +9.9,[3] which is over four magnitudes lower than Vesta.

Its orbit is slightly more eccentric than that of Hygiea (15% versus 12%) but differs from Hygiea's in its much greater inclination and slightly shorter period. Another difference is that Interamnia's perihelion is located on the opposite side from the perihelia of the "big four", so that Interamnia at perihelion is actually closer to the Sun than Ceres and Pallas are at the same longitude. It is unlikely to collide with Pallas because their nodes are located too far apart, whilst although its nodes are located on the opposite side from those of Ceres, it is generally clear of Ceres when both cross the same orbital plane and a collision is again unlikely.


IRAS measurements in 1983 estimated the asteroid to be 317 ± 5 km in diameter.[1] An occultation in 1996 produced a diameter of 329 km.[8] Observations of a favorable occultation of a bright 6.6 magnitude star on March 23, 2003, produced thirty-five chords indicating an ellipsoid of 350×304 km,[9][10] thus giving the asteroid a geometric mean diameter of 326 km.


In 2001, Michalak estimated Interamnia to have a mass of 6.9×1019 kg. Michalak's estimate depends on the masses of 19 Fortuna, 29 Amphitrite, and 16 Psyche; thus this mass was obtained assuming an incomplete dynamical model.[11]

In 2007, Baer and Chesley estimated Interamnia to have a mass of (7.12±0.84)×1019 kg.[12] As of 2010, Baer suggests Interamnia has a mass of only (3.90±0.18)×1019 kg.[13] This makes it more massive than 511 Davida, though the error bars overlap.[13]

Goffin's 2014 astrometric reanalysis gives an even lower mass of 2.725 ± 0.12×1019 kg (and has 3.00 ± 0.1 ×1019 kg for 511 Davida).[14]

Animation of 704 Interamnia's orbit 2000-2020
   Sun   Earth ·    Mars ·   Jupiter ·    704 Interamnia
The Transiting Exoplanet Survey Satellite (TESS) observed 704 Interamnia passing close to a target star, TIC 14802783, on 18/01/19.

See also[edit]



  1. ^ a b c d e "JPL Small-Body Database Browser: 704 Interamnia (1910 KU)" (2008-04-14 last obs). Retrieved 7 May 2016.
  2. ^ a b c d e f Hanuš, J.; Vernazza, P.; Viikinkoski, M.; Ferrais, M.; Rambaux, N.; Podlewska-Gaca, E.; et al. (29 November 2019). "(704) Interamnia: A transitional object between a dwarf planet and a typical irregular-shaped minor body". arXiv:1911.13049 [astro-ph.EP].
  3. ^ a b "Bright Minor Planets 2007". Minor Planet Center. Retrieved 21 May 2008.[permanent dead link]
  4. ^ Pitjeva, E. V. (2005). "High-Precision Ephemerides of Planets—EPM and Determination of Some Astronomical Constants" (PDF). Solar System Research. 39 (3): 176–186. Bibcode:2005SoSyR..39..176P. doi:10.1007/s11208-005-0033-2. Archived from the original (PDF) on 31 October 2008. 15 = 0.0124
  5. ^ https://arxiv.org/pdf/1911.13049.pdf
  6. ^ https://www.semanticscholar.org/paper/The-geologically-recent-giant-impact-basins-at-Schenk-O'brien/c4022b20a7042ae75992b87a27cfa1e853cfbbb1
  7. ^ https://www.eso.org/public/archives/releases/sciencepapers/eso1918/eso1918a.pdf
  8. ^ Buie, Marc W.; Wasserman; Millis (1997). "Occultation of GSC 23450183 by (704) Interamnia on 1996 December 17". American Astronomical Society. 29: 973. Bibcode:1997DPS....29.0710B.
  9. ^ Nugent, Richard (23 March 2003). "704 Interamnia 2003 Mar 23". Richard's Astronomy Pages. Archived from the original on 27 December 2008. Retrieved 3 December 2008.
  10. ^ MacRobert, Alan (13 March 2014). "Asteroid to Black Out Bright Star Regulus". Sky & Telescope.
  11. ^ Michalak, G. (2001). "Determination of asteroid masses". Astronomy & Astrophysics. 374 (2): 703–711. Bibcode:2001A&A...374..703M. doi:10.1051/0004-6361:20010731. Archived from the original on 4 December 2012. Retrieved 4 November 2008.
  12. ^ Baer, Jim; Steven R. Chesley (2008). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris". Celestial Mechanics and Dynamical Astronomy. Springer Science+Business Media B.V. 2007. 100 (2008): 27–42. Bibcode:2008CeMDA.100...27B. doi:10.1007/s10569-007-9103-8.
  13. ^ a b Baer, James (2010). "Recent Asteroid Mass Determinations". Personal Website. Archived from the original on 2 July 2013. Retrieved 13 February 2011.
  14. ^ Goffin, Edwin (2014). "Astrometric asteroid masses: A simultaneous determination". Astronomy & Astrophysics. 565: A56. arXiv:1402.4241. Bibcode:2014A&A...565A..56G. doi:10.1051/0004-6361/201322766.

External links[edit]