Theia (planet)
Theia (/ˈθiːə/) 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.[1][2] Such a collision, with the two planets' cores and mantles fusing, could explain why
Name
In Greek mythology, Theia was one of the Titans, the sister of Hyperion whom she later married, and the mother of Selene, the goddess of the Moon,[6] a story that parallels the planet Theia's theorized role in creating the Moon.[7]
Orbit
Theia is hypothesized to have orbited in the L4 or L5 configuration presented by the Earth–Sun system, where it would tend to remain. If this were the case it might have grown to a size comparable to Mars, with a diameter of about 6,102 kilometres (3,792 miles).[citation needed] Gravitational perturbations by Venus could have put it onto a collision course with the early Earth.[8]
Collision
According to the
Initially, the hypothesis supposed that Theia had struck Earth with a glancing blow
In contrast, evidence published in January 2016 suggests that the impact was indeed a head-on collision and that Theia's remains are on Earth and the Moon.[12][13][14]
Hypotheses
From the beginning of modern astronomy, there have been at least four hypotheses for the origin of the Moon:
- A single body split into Earth and Moon
- The Moon was captured by Earth's gravity (as most of the outer planets' smaller moons were captured)
- The Earth and Moon formed at the same time when the protoplanetary disk accreted
- The Theia-impact scenario described above
The lunar rock samples retrieved by Apollo astronauts were found to be very similar in composition to Earth's crust, and so were likely removed from Earth in some violent event.[12][15][16]
By 2012, theories found Theia could explain why
See also
References
- ^ Wolpert, Stuart (January 12, 2017). "UCLA Study Shows the Moon is Older Than Previously Thought". scitechdaily.com. UCLA. Retrieved 23 March 2022.
- ^ "The Theia Hypothesis: New Evidence Emerges that Earth and Moon Were Once the Same". The Daily Galaxy. 2007-07-05. Archived from the original on 2017-06-19. Retrieved 2013-11-13.
- ^ Sample, Ian (November 1, 2023). "Blobs near Earth's core are remnants of collision with another planet, study says". The Guardian.
- ^ a b Chang, Kenneth (1 November 2023). "A 'Big Whack' Formed the Moon and Left Traces Deep in Earth, a Study Suggests - Two enormous blobs deep inside Earth could be remnants of the birth of the moon". The New York Times. Archived from the original on 1 November 2023. Retrieved 2 November 2023.
- ISSN 0019-1035.
- ISBN 9783319318363.
- ^ "Selene | Origin and meaning of selene by Online Etymology Dictionary".
- ^ a b "STEREO Hunts for Remains of an Ancient Planet near Earth". NASA. 2009-04-09. Archived from the original on 2013-11-13. Retrieved 2013-11-13.
- S2CID 118421530.
- S2CID 84558.
- ^ "Faceoff! The Moon's oddly different sides", Astronomy, August 2014, 44–49.
- ^ a b Nace, Trevor (2016-01-30). "New Evidence For 4.5 Billion Year Old Impact Formed Our Moon". Forbes. Retrieved 2016-01-30.
- S2CID 6548599.
- ^ Wolpert, Stuart (January 28, 2016). "Moon was produced by a head-on collision between Earth and a forming planet". UCLA newsroom. UCLA.
- S2CID 30903580.
- S2CID 119226112.
- ^ "A New Model for the Origin of the Moon". SETI Institute.
- ^ Yuan, Qian; Li, Mingming; Desch, Steven J.; Ko, Byeongkwan (2021). "Giant impact origin for the large low shear velocity provinces" (PDF). 52nd Lunar and Planetary Science Conference. Retrieved 27 March 2021.
- BBC Future, by Zaria Gorvett, 12 May 2022
- from the original on 2 November 2023. Retrieved 2 November 2023.