Radiation astronomy/Scattered disks

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The diagram shows scattered disc objects out to 100 AU. Credit: Eurocommuter.

Scattered Disk Objects (up to 100 AU): Kuiper Belt objects are shown in grey, resonant objects within the Scattered Disk are shown in green.

The position of an object represents

  • its orbit’s semi-major axis a in AU and the orbital period in years (horizontal axis)
  • its orbit’s inclination i in degrees (vertical axis).

The size of the circle illustrates the object’s size relative to others. For a few large objects, the diameter drawn represents the best current estimates. For all others, the circles represent the absolute magnitude of the object.

The eccentricity of the orbit is shown indirectly by a segment extending from the left (perihelion) to the aphelion to the right. In other words, the segment illustrates the variations of the object's distance from the Sun. Objects with nearly circular orbits will show short segments while highly elliptical orbits will be represented by long segments.

Main resonances with Neptune are marked with vertical bars; 1:1 marks the position of Neptune’s orbit (and its Trojan asteroids), 2:3 marks the orbit of Pluto (and plutinos) etc.


The dwarf planet Eris is the largest known scattered-disc object (center), with its moon Dysnomia (left of object). Credit: NASA, ESA, and Michael E. Brown.

The scattered disc (or scattered disk) is a distant region of the Solar System that is sparsely populated by icy minor planets, a subset of the broader family of trans-Neptunian objects. The scattered-disc objects (SDOs) have orbital eccentricities ranging as high as 0.8, inclinations as high as 40°, and perihelia greater than 30 astronomical units (4.5 x 109 km; 2.8 x 109 mi.). While the nearest distance to the Sun approached by scattered objects is about 30–35 AU, their orbits can extend well beyond 100 AU. This makes scattered objects "among the most distant and cold objects in the Solar System".[1]


  1. Maggie Masetti. (2007). Cosmic Distance Scales – The Solar System. Website of NASA's High Energy Astrophysics Science Archive Research Center. Retrieved 2008 07-12.