Overview
Herse is one of Jupiter's many small irregular satellites. Discovered in 2003 by a team led by Brett J. Gladman and colleagues, it was provisionally designated S/2003 J 17 until receiving the name Herse in 2009. With a diameter of roughly 2 kilometres, Herse is far too small to be spherical and is observable only with large telescopes and targeted surveys of the Jovian system.
Orbit and physical characteristics
Herse follows a distant, inclined, retrograde orbit around Jupiter. Its mean orbital radius is about 22,134,000 kilometres and it completes one orbit in roughly 672.716 days. The satellite's orbit is tilted steeply relative to the plane of the Solar System — an inclination of approximately 162° to the ecliptic — and is noticeably eccentric.
- Average orbital distance: ~22,134,000 km
- Orbital period: ~672.716 days
- Inclination: ~162° to the ecliptic (source)
- Eccentricity: ~0.2379 (source)
- Approximate diameter: ~2 km
Discovery and name
The moon was discovered in 2003 as part of a wave of faint Jovian satellites identified in the early 21st century. These discoveries were enabled by improved detectors and wide-field surveys. After its provisional designation S/2003 J 17, the International Astronomical Union assigned the name Herse in 2009, following the convention of naming Jovian moons after characters from classical mythology related to Zeus/Jupiter.
Group membership and origin
Herse is generally listed as a member of the Carme group, a collection of irregular, retrograde moons that share similar orbits and spectral characteristics. The Carme group orbits at distances roughly between 23,000,000 and 24,000,000 km from Jupiter and at inclinations near 165°. Herse lies slightly closer to Jupiter than the typical range and is often described as the closest known member of this group. Members of the Carme group are non-spherical in shape and show similar reddish spectral properties, suggesting they may be fragments of a captured and subsequently disrupted progenitor body (Carme group, non-spherical).
Significance and observations
Although Herse is too small to influence Jupiter or its larger moons, studying such objects is important for understanding the capture and collisional history of the Jovian satellite system. Their orbits and compositions provide clues about past events that shaped the population of irregular satellites. Continued observations refine orbital elements and help test models of group membership and origin, but because of its faintness Herse will remain a target mainly for specialized telescopic programs.