Damocloid asteroid

From Wikipedia, the free encyclopedia

Damocloids are asteroids such as 5335 Damocles and 1996 PW that have Halley family or long-period highly eccentric orbits typical of periodic comets such as Comet Halley, but without showing a cometary coma or tail.

Damocloids are believed to be nuclei of Halley-type comets that have lost all their volatile materials due to outgassing. Such comets are believed to originate from the Oort cloud. This hypothesis is strengthened by the fact that a number of objects thought to be Damocloids (and assigned minor planet provisional designations) subsequently showed a coma and were confirmed to be comets: C/2001 OG₁₀₈ (LONEOS), C/2002 CE₁₀ (LINEAR), C/2002 VQ₉₄ (LINEAR), C/2004 HV₆₀ (Spacewatch) and possibly others. Another strong indication of cometary origin is the fact that some Damocloids have retrograde orbits, unlike any other asteroids.

As of July 2007, 36 Damocloids were known. Their average radius is eight kilometers. The albedos of four Damocloids have been measured, and they are among the darkest objects known in the Solar system. Damocloids are reddish in color, but not as red as many Kuiper belt objects or Centaurs.