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Theia (/ ˈ θ iː ə /) is a hypothesized ancient planet in the early Solar System which, according to the giant-impact hypothesis, collided with the early Earth around 4.5 billion years ago, with some of the resulting ejected debris coalescing to form the Moon.
Astronomers think the collision between Earth and Theia happened at about 4.4 to 4.45 billion years ago ; about 0.1 billion years after the Solar System began to form. [15] [16] In astronomical terms, the impact would have been of moderate velocity. Theia is thought to have struck Earth at an oblique angle when Earth was nearly fully formed.
Theia or Orpheus, [21] a Mars-sized impactor believed to have collided with the Earth roughly 4.5 billion years ago; an event which created the Moon. Evidence from 2019 suggests that it may have originated in the outer Solar System. [22] Vulcan, a hypothetical planet once believed to exist inside the orbit of Mercury. Initially proposed as the ...
Theia's mythological role as the mother of the Moon goddess Selene is alluded to in the application of the name to a hypothetical planet that, according to the giant impact hypothesis, collided with the Earth and created the Moon, paralleling the mythological Theia's role as the mother of Selene. [17]
These include 54509 YORP, (85770) 1998 UP 1, 2002 AA 29, (419624) 2010 SO 16, 2009 BD, and 2015 SO 2 which exist in resonant orbits similar to Cruithne's. 2010 TK 7 and (614689) 2020 XL 5 are the only two identified Earth trojans. Hungaria asteroids were found to be one of the possible sources for co-orbital objects of the Earth with a lifetime ...
The Moon-to-Earth mass ratio of 0.01230 (≈ 1 ⁄ 81) is also notably close to 1 when compared to all other satellite-to-planet ratios. Consequently, some scientists view the Earth–Moon system as a double planet as well, though this is a minority view.
Schematic diagram of the orbits of the fictional planets Vulcan, Counter-Earth, and Phaëton in relation to the five innermost planets of the Solar System.. Fictional planets of the Solar System have been depicted since the 1700s—often but not always corresponding to hypothetical planets that have at one point or another been seriously proposed by real-world astronomers, though commonly ...
Many TNOs are often just assumed to have Pluto's density of 2.0 g/cm 3, but it is just as likely that they have a comet-like density of only 0.5 g/cm 3. [ 4 ] For example, if a TNO is incorrectly assumed to have a mass of 3.59 × 10 20 kg based on a radius of 350 km with a density of 2 g/cm 3 but is later discovered to have a radius of only 175 ...