28978 IXION

'28978 Ixion' (IPA pronunciation: , '') is a Kuiper belt object discovered on May 22, 2001. Ixion is a plutino (an object that has a 2:3 orbital resonance with Neptune); its estimated diameter of 800 km makes it the second largest plutino. It is named after Ixion, a figure from Greek mythology; it previously had the provisional designation ''.

Contents

Physical characteristics

Orbit

See also

References

External links

Physical characteristics

Ixion is moderately red (slightly redder than 50000 Quaoar) and it has a higher albedo (0.15) than the mid-sized red cubewanos.
The latest spectroscopic results indicate that Ixion's surface is a mixture of dark carbon and tholin, which is a heteropolymer formed by irradiation of clathrates of water and organic compounds (see TNO spectra). Water ice absobtion lines (1.5 and 2μm) were absent (Licandro ''et al.'' 2002). Unlike Varuna, Ixion does not show greater reflectivity for longer waves (the so-called red slope) in infrared.

Orbit

Ixion and Pluto follow similar but differently oriented orbits: Ixion’s perihelion is below the ecliptic whereas Pluto's is above it. Uncharacteristically for bodies locked in resonance with Neptune (such as Orcus), Ixion approaches Pluto with less than 20 degrees of angular separation. Ixion is currently crossing the ecliptic heading below, and will reach its perihelion in 2070. Pluto has passed its perihelion (1989) and is descending toward the ecliptic. Ixion's orbital period is almost 250 Earth years, about 0.5% larger than Pluto's.

See also

★ Comparison of colours of trans-Neptunian objects

References

★ Pre-print about Ixion's surface from the Planetary Systems Research group of the University of Helsinki

★ Pre-print on arXiv

★ ''Size estimates of some optically bright KBOs'', W. J. Altenhoff, F. Bertoldi and K. M. Menten, , , Astronomy & Astrophysics, 2004

External links

★ AstDys orbital elements

★ Orbit simulation from JPL (Java).