The Solar System - Word Search - PUZZLE #45 SEDNA - August 2025

PUZZLE #45 - SEDNA 

IN-CONTEXT WORD DEFINITIONS

Oort Cloud: Sedna's orbit extends far beyond the Kuiper Belt and into what some astronomers have called the "inner Oort cloud." The Oort Cloud is a hypothetical spherical region of icy objects believed to be the source of long-period comets. Sedna's distant perihelion (closest approach to the Sun) sets it apart from typical Kuiper Belt objects, leading some to consider it an inhabitant of this inner Oort cloud region.

Sednoid: This is a new orbital class of trans-Neptunian objects with characteristics similar to Sedna. Sednoids have large semi-major axes, very distant perihelia (greater than 60 AU), and highly eccentric orbits, remaining largely unaffected by the gravity of the known planets. Sedna is the prototype of this class, which also includes objects like 2012 VP113.

Reddest: Sedna is known for being one of the reddest objects in the Solar System, with a color nearly as red as Mars. This deep red hue is thought to be caused by a surface coating of hydrocarbon sludge, called tholins. These tholins are formed when simpler organic compounds on Sedna's surface are exposed to ultraviolet radiation over billions of years.

Methane Ice: Spectroscopic analysis of Sedna's surface has revealed the presence of methane ice. This, along with water ice and tholins, makes up its surface composition. However, the weak methane absorption bands suggest the methane ice is ancient, implying Sedna's surface never gets warm enough for methane to sublimate and redeposit as snow, as it does on Pluto or Triton.

Longest Period: Sedna holds the record for the longest orbital period of any known object in the Solar System of its size or larger, taking approximately 11,400 Earth years to complete one orbit around the Sun. This extremely long period is due to its highly eccentric and distant orbit.

Detached Object: Sedna is categorized as a "detached object" because its perihelion distance (76 AU) is so far from Neptune's orbit (average 30.1 AU) that its orbit is not strongly influenced by the giant planets. This distinguishes it from scattered disk objects, whose orbits are significantly shaped by Neptune's gravity.

Scattered Disc: While initially considered a member of the scattered disc, this classification has been contested because Sedna's perihelion is too distant to have been perturbed by Neptune. However, the concept of an "extended scattered disc" or "detached objects," which includes Sedna and other similar objects, has been discussed to acknowledge the dynamical gradation between the scattered disc and the inner Oort Cloud.

Voyager: The Voyager spacecraft are well beyond Sedna's current distance from the Sun, traveling further into interstellar space. While the Pioneer missions have already ceased functioning due to RTG limitations, the Voyager missions continue to operate further out in space. The Voyager probes were launched in 1977, and even at Sedna's perihelion, it would still take a spacecraft a long time to reach it.

Planet Nine: Sedna's unusual orbit, along with those of other extreme trans-Neptunian objects, has been used as evidence supporting the hypothesis of a hypothetical "Planet Nine". According to this theory, a super-Earth planet, roughly six times the mass of Earth, in a highly eccentric orbit far beyond Neptune, could gravitationally shepherd these distant objects into their observed clustered orbits.

Secret Word: Sedna is considered a dwarf planet candidate. While it is bright and large enough to be spherical (a key characteristic of dwarf planets), its distant location makes it challenging to confirm if it has cleared its orbital path of other objects, which is required for official classification as a dwarf planet.