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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 ...
– Unsuccessful soft landing, intentional hard landing, or mission still in progress. – Successful soft landing with intelligible data return. The tannish hue indicates extraterrestrial soil. – Successful soft landing, intelligible data return, and sample return to Earth. The greenish hue indicates terrestrial return.
1959 – Explorer 6 sends the first image of the entire Earth from space. [178] 1959 – Luna 3 sends the first images of another celestial body, the Moon, from space, including its unseen far side. [179] 1962 – Mariner 2 Venus flyby performs the first closeup observations of another planet. [180]
The great majority of Earth-orbiting satellites. Space probes leaving Earth orbit that are not concerned with Solar System exploration (such as space telescopes targeted at distant galaxies, cosmic background radiation observatories, and so on). Probes that failed at launch.
The first artificial object sent into space was the Soviet satellite Sputnik 1, launched on 4 October 1957, which successfully orbited Earth until 4 January the following year. [65] The American probe Explorer 6, launched in 1959, was the first satellite to image Earth from space.
Irregular moons are probably minor planets that have been captured from surrounding space. Most irregular moons are less than 10 kilometres (6.2 mi) in diameter. The earliest published discovery of a moon other than Earth's was by Galileo Galilei, who discovered the four Galilean moons orbiting Jupiter in 1610. Over the following three ...
The last time all eight planets were aligned was on Dec. 28, 2022. On Jan. 18, 2025, there will be six planets in the alignment: Mercury, Mars, Jupiter, Uranus, Neptune and Saturn.
The Hindu cosmological time cycles explained in the Surya Siddhanta, give the average length of the sidereal year (the length of the Earth's revolution around the Sun) as 365.2563627 days, which is only 1.4 seconds longer than the modern value of 365.256363004 days. [10]