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Earth's atmosphere photographed from the International Space Station.The orange and green line of airglow is at roughly the altitude of the Kármán line. [1]The Kármán line (or von Kármán line / v ɒ n ˈ k ɑːr m ɑː n /) [2] is a conventional definition of the edge of space; it is widely but not universally accepted.
For the small outer irregular moons of Uranus, such as Sycorax, which were not discovered by the Voyager 2 flyby, even different NASA web pages, such as the National Space Science Data Center [6] and JPL Solar System Dynamics, [5] give somewhat contradictory size and albedo estimates depending on which research paper is being cited.
Outer space (or simply space) is the expanse that exists beyond Earth's atmosphere and between celestial bodies. [1] It contains ultra-low levels of particle densities , constituting a near-perfect vacuum [ 2 ] of predominantly hydrogen and helium plasma , permeated by electromagnetic radiation , cosmic rays , neutrinos , magnetic fields and dust .
Saturn has 146 known moons, 63 of which have formal names. [12] [11] It is estimated that there are another 100 ± 30 outer irregular moons larger than 3 km (2 mi) in diameter. [98] In addition, there is evidence of dozens to hundreds of moonlets with diameters of 40–500 meters in Saturn's rings, [99] which are not considered to be true moons.
Stability means that satellites in DRO do not need to use station keeping propellant to stay in orbit. The lunar DRO is a high lunar orbit with a radius of approximately 61,500 km. [24] This was proposed [by whom?] in 2017 as a possible orbit for the Lunar Gateway space station, outside Earth-Moon L1 and L2. [20]
Radar is used to measure the distance between the orbits of the Earth and of a second body. From that measurement and the ratio of the two orbit sizes, the size of Earth's orbit is calculated. The Earth's orbit is known with an absolute precision of a few meters and a relative precision of a few parts in 100 billion (1 × 10 −11).
The Kármán line, at 100 km (62 mi) or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi).
This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...