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The listed objects currently include most objects in the asteroid belt and moons of the giant planets in this size range, but many newly discovered objects in the outer Solar System are missing, such as those included in the following reference. [58] Asteroid spectral types are mostly Tholen, but some might be SMASS.
Thus, the Sun occupies 0.00001% (1 part in 10 7) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly 1 millionth (10 −6) that of the Sun. Jupiter, the largest planet, is 5.2 AU from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi), whereas the most distant planet, Neptune, is 30 AU ...
The observable universe contains as many as an estimated 2 trillion galaxies [36] [37] [38] and, overall, as many as an estimated 10 24 stars [39] [40] – more stars (and, potentially, Earth-like planets) than all the grains of beach sand on planet Earth. [41] [42] [43] Other estimates are in the hundreds of billions rather than trillions.
There are eight planets within the Solar System; planets outside of the solar system are also known as exoplanets. Artist's concept of the potentially habitable exoplanet Kepler-186f As of 19 December 2024, there are 5,811 confirmed exoplanets in 4,340 planetary systems , with 973 systems having more than one planet . [ 1 ]
Planet Taphao Thong was discovered in 1996 and was one of the first exoplanets to be discovered. [48] The planet was the first long-period extrasolar planet discovered. The other planets were discovered later. [49] Nu 2 Lupi: Lupus: 15 h 21 m 49.57 s: −48° 19′ 01.1″ 5.65: 47: G2V: 0.906: 5664: 10.36: 3
Many of the stars in a galaxy have planets. ... Some disputed [60] estimates for the total size of the universe, if ... equivalent to about 5 protons per cubic ...
Some of these planets orbit multiple stars at the same time. Certain planets are so close to their star that it takes only a handful of days to make one revolution, compared to the Earth which ...
They generally agree that several other trans-Neptunian objects (TNOs) may be large enough to be dwarf planets, given current uncertainties. However, there has been disagreement on the required size. Early speculations were based on the small moons of the giant planets, which attain roundness around a threshold of 200 km radius. [49]