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Parts-per-million chart of the relative mass distribution of the Solar System, each cubelet denoting 2 × 10 24 kg. This article includes a list of the most massive known objects of the Solar System and partial lists of smaller objects by observed mean radius.
Compared to many extrasolar systems, the Solar System stands out in lacking planets interior to the orbit of Mercury. [ 70 ] [ 71 ] The known Solar System lacks super-Earths , planets between one and ten times as massive as the Earth, [ 70 ] although the hypothetical Planet Nine , if it does exist, could be a super-Earth orbiting in the edge of ...
The Milky Way contains between 100 and 400 billion stars [12] [13] and at least that many planets. [150] An exact figure would depend on counting the number of very-low-mass stars, which are difficult to detect, especially at distances of more than 300 ly (90 pc) from the Sun.
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.
For comparison, the Milky Way has a diameter of at least 26,800 parsecs (87,400 ly) [9] [a] and is separated from the Andromeda Galaxy, its nearest large neighbour, by just over 750,000 parsecs (2.5 million ly). [12]
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 ]
The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31 , M31 , and NGC 224 . Andromeda has a D 25 isophotal diameter of about 46.56 kiloparsecs (152,000 light-years ) [ 8 ] and is approximately 765 kpc (2.5 million light-years ...
Vesta and Pallas are nonetheless sometimes considered small terrestrial planets anyway by sources preferring a geophysical definition, because they do share similarities to the rocky planets of the inner solar system. [56] The fourth-largest asteroid, Hygiea (radius 216.5 ± 4 km), is icy.