(1297) Quadea, the Incredible Shrinking Asteroid

David Dunham, IOTA

2011 November 16

The Uncertain Size of Quadea• In 1983, the Infra-Red Astronomical Satellite (IRAS)

measured Quadea’s mean diameter to be 66 km• For many years, that value was unchallenged• In 2006, the Japanese AKARI IR mission, whose data

were recently published, showed that Quadea’s diameter is only 25 km

• Which one is right, or better?• An occultation on Nov. 7/8 might tell• The occultation prediction was updated with the AKARI

value only about ten days before the occ’n• Quadea was discovered 1934 Jan. 7 at Heidelberg,

Germany by Karl Reinmuth, who named it for the parents-in-law of his brother

• It is a member of the Eos family of asteroids, which have an unusual “K-class” spectrum, considered low-albedo objects, but Tholen noted that these asteroids have “featureless S-class” spectra; S-class asteroids have relatively large albedoes.

Occultation of SAO 56119 on Nov. 8 UT

Stations for the occultation in Calif. & Nev.

Sky-Plane Plot of the Occultation

The mean diameter of27 km from the occ’nis just over the 25 kmAKARI diameter, whichIs clearly better thanthe IRAS diameter.