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.
|Discovered by||Vincenzo Cerulli|
|Discovery date||2 October 1910|
|MPC designation||(704) Interamnia|
|1910 KU; 1952 MW|
|Epoch 31 July 2016 (JD 2457600.5)|
|Uncertainty parameter 0|
|Observation arc||102.38 yr (37395 d)|
|Aphelion||3.5293 AU (527.98 Gm)|
|Perihelion||2.5857 AU (386.82 Gm)|
|3.0575 AU (457.40 Gm)|
|5.35 yr (1952.8 d)|
Average orbital speed
|0° 11m 3.66s / day|
|Dimensions||(350.3 ± 0.8) × (303.6 ± 1.2) km|
326 (mean of 350x304)
317 ± 5 km IRAS
|0.364 d 2|
8.727 h (0.3636 d)
|9.9 to 13.0|
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.
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 there exist 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). Its apparently high bulk density (though subject to much error) suggests an extremely solid body entirely without internal porosity or traces of water. This also strongly suggests that Interamnia is large enough to have fully withstood all the collisions that have occurred in the asteroid belt since the Solar System was formed.
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, 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. An occultation in 1996 produced a diameter of 329 km. 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, 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.
In 2007, Baer and Chesley estimated Interamnia to have a mass of (7.12±0.84)×1019 kg. As of 2010[update], Baer suggests Interamnia has a mass of only (3.90±0.18)×1019 kg. This makes it more massive than 511 Davida, though the error bars overlap.