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Planet Nine is a hypothetical ninth planet in the outer region of the Solar System. [2] [4] Its gravitational effects could explain the peculiar clustering of orbits for a group of extreme trans-Neptunian objects (ETNOs), bodies beyond Neptune that orbit the Sun at distances averaging more than 250 times that of the Earth i.e. over 250 astronomical units (AUs).
Ceres (minor-planet designation: 1 Ceres) is a dwarf planet in the middle main asteroid belt between the orbits of Mars and Jupiter.It was the first known asteroid, discovered on 1 January 1801 by Giuseppe Piazzi at Palermo Astronomical Observatory in Sicily, and announced as a new planet.
The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across and larger than meteoroids, to Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum ...
Nonetheless, collisions between large asteroids occur and can produce an asteroid family, whose members have similar orbital characteristics and compositions. Individual asteroids within the belt are categorized by their spectra, with most falling into three basic groups: carbonaceous , silicate , and metal-rich .
In 1975, astronomers Clark R. Chapman, David Morrison, and Ben Zellner developed a simple taxonomic system for asteroids based on color, albedo, and spectral shape.The three categories were labelled "C" for dark carbonaceous objects, "S" for stony (silicaceous) objects, and "U" for those that did not fit into either C or S. [2] This basic division of asteroid spectra has since been expanded ...
Standard asteroid physical characteristics. For most numbered asteroids, almost nothing is known apart from a few physical parameters and orbital elements. Some physical characteristics can only be estimated. The physical data is determined by making certain standard assumptions.
Below are the descriptions of the three largest bodies in the asteroid belt. They are all considered to be relatively intact protoplanets, a precursor stage before becoming a fully-formed planet (see List of exceptional asteroids): [143] [144] [145] Ceres (2.55–2.98 AU) is the only dwarf planet in the asteroid belt. [146]
A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk, while the two are similar. While they are similar, an accretion disk is hotter, and spins much faster.