Sedna

Definition

Sedna is a dwarf planet located in the outer reaches of the Solar System, far beyond the orbit of Neptune. It is one of the most distant known objects in the Solar System, with a highly elliptical and distant orbit that takes approximately 11,400 years to complete.

5 Must Know Facts For Your Next Test

1. Sedna has one of the most distant and eccentric orbits of any known object in the Solar System, with a perihelion (closest approach to the Sun) of approximately 76 astronomical units (AU).
2. The discovery of Sedna in 2003 led to a re-evaluation of the definition of a planet, ultimately leading to the creation of the dwarf planet classification.
3. Sedna is estimated to be approximately 995 kilometers (620 miles) in diameter, making it one of the largest known dwarf planets in the Solar System.
4. The origin of Sedna's highly unusual orbit is a subject of ongoing scientific debate, with some hypotheses suggesting the influence of an undiscovered massive distant planet.
5. Sedna's extreme distance from the Sun and slow orbital period make it a challenging target for direct observation and study, but its existence provides valuable insights into the formation and evolution of the outer Solar System.

Review Questions

• Describe the key characteristics of Sedna's orbit and how it differs from the orbits of the major planets in the Solar System.
  • Sedna has an extremely distant and highly elliptical orbit, with a perihelion (closest approach to the Sun) of approximately 76 astronomical units (AU) and an aphelion (farthest distance from the Sun) of over 900 AU. This makes Sedna one of the most distant known objects in the Solar System, with an orbital period of approximately 11,400 years. In contrast, the major planets in the Solar System have relatively circular orbits that are much closer to the Sun, with the farthest planet, Neptune, orbiting at an average distance of about 30 AU.
• Explain how the discovery of Sedna contributed to the re-evaluation and creation of the dwarf planet classification in the Solar System.
  • The discovery of Sedna in 2003 led astronomers to re-evaluate the definition of a planet, as Sedna did not fit neatly into the existing categories of planets, asteroids, or comets. Sedna's large size, roughly spherical shape, and distant orbit suggested that it was a distinct class of object. This, along with the discovery of other similar trans-Neptunian objects, ultimately led to the creation of the dwarf planet classification, which includes Sedna and other celestial bodies that orbit the Sun but have not cleared their orbital path of other objects.
• Discuss the ongoing scientific debate surrounding the possible influence of an undiscovered massive distant planet on Sedna's unusual orbit, and how this relates to our understanding of the formation and evolution of the outer Solar System.
  • The highly unusual and distant orbit of Sedna has led some scientists to hypothesize the existence of an undiscovered massive planet in the outer Solar System, sometimes referred to as 'Planet X' or 'Planet Nine.' The reasoning is that the gravitational influence of such a planet could explain Sedna's extreme orbital characteristics, as well as the orbits of other distant trans-Neptunian objects. While the existence of this hypothetical planet remains unconfirmed, the search for it and the study of Sedna's orbit provide valuable insights into the formation and evolution of the outer Solar System, particularly the processes that shaped the orbits of the most distant objects. Understanding the dynamics of the outer Solar System is crucial for piecing together the full story of how our planetary system came to be.

Related terms

Dwarf Planet: A celestial body that orbits the Sun, is large enough to be nearly round in shape, but has not cleared the area of its orbit of other objects and is not a satellite.

Kuiper Belt: A region of the Solar System beyond the orbit of Neptune, containing many small bodies, including dwarf planets, comets, and other icy objects.

Trans-Neptunian Object: Any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune.