Question: Zsigmondy is a crater that exists on an astronomical body that orbits which planet ?
Context: HD 171238 b is an extrasolar planet which orbits the G-type main sequence star HD 171238, located approximately 164 light years away in the constellation Sagittarius.  This planet has minimum mass two and a half times greater than Jupiter and orbits two times closer to the star than Jupiter to the Sun.  However this planet orbits in an eccentric orbit, about two astronomical units difference between periastron and apastron distances.  This planet was discovered in August 2009 by using the radial velocity method in La Silla Observatory, Chile. An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe.  In astronomy, the terms "object" and "body" are often used interchangeably.  However, an astronomical body or celestial body is a single, tightly bound contiguous entity, while an astronomical or celestial "object" is a complex, less cohesively bound structure, that may consist of multiple bodies or even other objects with substructures. In celestial mechanics, an orbital resonance occurs when orbiting bodies exert a regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly this relationship is found for a pair of objects.  The physics principle behind orbital resonance is similar in concept to pushing a child on a swing, where the orbit and the swing both have a natural frequency, and the other body doing the "pushing" will act in periodic repetition to have a cumulative effect on the motion.  Orbital resonances greatly enhance the mutual gravitational influence of the bodies, i.e. their ability to alter or constrain each other's orbits.  In most cases, this results in an "unstable" interaction, in which the bodies exchange momentum and shift orbits until the resonance no longer exists.  Under some circumstances, a resonant system can be stable and self-correcting, so that the bodies remain in resonance.  Examples are the 1:2:4 resonance of Jupiter's moons Ganymede, Europa and Io, and the 2:3 resonance between Pluto and Neptune.  Unstable resonances with Saturn's inner moons give rise to gaps in the rings of Saturn.  The special case of 1:1 resonance between bodies with similar orbital radii causes large Solar System bodies to eject most other bodies sharing their orbits; this is part of the much more extensive process of clearing the neighbourhood, an effect that is used in the current definition of a planet. A crater chain is a line of craters along the surface of an astronomical body.  The descriptor term for crater chains is catena (plural catenae), as specified by the International Astronomical Union's rules on planetary nomenclature. The Moon is an astronomical body that orbits planet Earth, being Earth's only permanent natural satellite.  It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits (its primary).  Following Jupiter's satellite Io, the Moon is second-densest satellite among those whose densities are known. Sinan is an impact crater on the planet Mercury, 147 kilometers in diameter.  It is located at 15.5°N, 29.8°W, northeast of the crater Yeats and southeast of the crater Li Po.  It has one craterlet on the south-southwestern side of the crater floor, and it has a symmetrical pit slightly west of the center.  Together with a smaller unnamed crater on its southern border, the crater Sinan forms a shape similar to that of the spade found in card games.  The crater is named after Mimar Sinan, a 16th-century Turkish architect.  The name was adopted by the International Astronomical Union in 1976. A comet is a small astronomical body which orbits the sun. Zsigmondy is a lunar crater located beyond the northwestern limb on the far side of the Moon.  Attached to the southeastern rim of the crater is the crater Omar Khayyam, which lies within the much larger Poczobutt.  Farther to the east, along the north rim of Poczobutt, is Smoluchowski. A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet (or sometimes another small Solar System body). Molière is an impact crater on the planet Mercury, 132 kilometers in diameter.  It is located at 15.6°N, 16.9°W, south of the crater Rodin, southeast of the crater Abu Nuwas, and northeast of the crater Asvaghosa.  The nearly circular rim of the crater is cut off into a flat edge on its southern and southwestern ends, and on its eastern side the rim is indented by a smaller crater.  The crater is named for the 17th century French dramatist and satirist Molière.  The name was approved by the International Astronomical Union in 1976.
Answer: Earth