704 Interamnia

One of the first photographic plates of 704 Interamnia obtained by the Italian astronomer Vincenzo Cerulli form the Observatory of Teramo (Italy). The image was taken in Oct. 1910; the path of the asteroid is shown in the zoom.

704 Interamnia is a very large 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.^[6]

Characteristics

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,^[5] 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.

Size

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.^[7] 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,^[2][8] thus giving the asteroid a geometric mean diameter of 326 km.

Mass

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.^[9]

In 2007, Baer and Chesley estimated Interamnia to have a mass of (7.12±0.84)×10¹⁹ kg.^[10] As of 2010, Baer suggests Interamnia has a mass of only (3.90±0.18)×10¹⁹ kg.^[4] This makes it more massive than 511 Davida, though the error bars overlap.^[4]

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.^[11]

See also

• List of Solar System objects by size

References

External links

• Animation of Asteroid Interamnia taken on April 1 & 2, 2003
• Interamnia Occultations Observed before 2003
• Occultation of GSC 23450183 by 704 Interamnia on 17 December 1996
• Occultation of HIP36189 by 704 Interamnia on 23 March 2003
• 704 Interamnia at the JPL Small-Body Database
  
  • Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters