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The largest of these may have a hydrostatic-equilibrium shape, but most are irregular. Most of the trans-Neptunian objects (TNOs) listed with a radius smaller than 200 km have " assumed sizes based on a generic albedo of 0.09" since they are too far away to directly measure their sizes with existing instruments.
These are lists of planets.A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk.
The timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the ...
The red dwarf stars are considered the smallest stars known, and representative of the smallest star possible. [64] [65] [66] Brown dwarf: WISEA 1810−1010: 0.067 0.655 7.29 46,840 km (29,110 mi) Brown dwarfs are not massive enough to build up the pressure in the central regions to allow nuclear fusion of hydrogen into helium.
The oldest stars contain few metals, whereas stars born later have more. This higher metallicity is thought to have been crucial to the Sun's development of a planetary system because the planets formed from the accretion of "metals". [82] The region of space dominated by the Solar magnetosphere is the heliosphere, which spans much of the Solar ...
A star is a massive luminous spheroid astronomical object made of plasma that is held together by its own gravity.Stars exhibit great diversity in their properties (such as mass, volume, velocity, stage in stellar evolution, and distance from Earth) and some of the outliers are so disproportionate in comparison with the general population that they are considered extreme.
The ancient Hebrews, like all the ancient peoples of the Near East, believed the sky was a solid dome with the Sun, Moon, planets and stars embedded in it. [5] In biblical cosmology, the firmament is the vast solid dome created by God during his creation of the world to divide the primal sea into upper and lower portions so that the dry land ...
Widely recognised as being among the largest known stars, [28] radius decreased to ~500 R ☉ during the 2020 great dimming event. [74] R Horologii: 635 [75] L/T eff: A red giant star with one of the largest ranges in brightness known of stars in the night sky visible to the unaided eye. Despite its large radius, it is less massive than the Sun.