Erriapus /ɛriˈæpəs/, or Saturn XXVIII (28), is a prograde irregular satellite of Saturn. It was discovered by Brett Gladman, John J. Kavelaars and colleagues in 2000, and given the temporary designation S/2000 S 10.[7][8] It was named Erriapo in August 2003[9] after Erriapus (also rendered Erriappus), a giant in Gaulish mythology; the name was changed from dative Erriapo to nominative Erriapus per IAU conventions in late 2007.[10][11]
 Discovery images of Erriapus taken by the CFHT in September 2000 | |
| Discovery[1] | |
|---|---|
| Discovered by | John J. Kavelaars et al. |
| Discovery date | 2000 |
| Designations | |
Designation | Saturn XXVIII |
| Pronunciation | /ɛriˈæpəs/ |
Named after | Erriap(p)us |
| S/2000 S 10 | |
| Orbital characteristics[2] | |
| Epoch 2000 January 1.5 | |
| 17 507 200 km | |
| Eccentricity | 0.462 |
| 871.1 d (2.38 yr) | |
| Inclination | 38.7 |
| Satellite of | Saturn |
| Group | Gallic group |
| Physical characteristics[3][4] | |
| Dimensions | 16.30 × 10 × 6.34 km (modeled)[5] |
Mean diameter | 10+50% −30% km |
| 28.15±0.25 h | |
| Albedo | 0.06 (assumed) |
Spectral type | light red B−V=0.83, R−V=0.49[6] |
| 23.0 | |
| 13.7 | |
Erriapus is about 10 kilometres in diameter, and orbits Saturn at an average distance of 17.5 Gm in 871 days.
As a member of the Gallic group of irregular satellites, which share similar orbital characteristics and a light-red colour, Erriapus is hypothesized to have its origin in the break-up of a common progenitor of the group,[6][12] or to be a fragment of its largest member, Albiorix.[13] It has a rotation period of 28.15±0.25 h, and is thought to rotate on its side, giving it similar seasons to those of Uranus.[14][15] With a fairly elongated shape, it is a candidate for a contact binary or binary moon.[4]