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Extraterrestrial life
Extraterrestrial life is life that may exist and originate outside the planet Earth, the only place in the universe currently known by humans to support life. Its existence is currently purely ... > more -
Magnetosphere
A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. Earth is surrounded by a magnetosphere, as are the magnetized planets ... > more -
Transit of Venus
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against (and hence obscuring a small portion of) the solar disk. During ... > more -
Space exploration
Space exploration is the physical exploration of outer space, both by human spaceflights and by robotic spacecraft. While the observation of objects in space—known as astronomy—pre-dates ... > more -
Outer space
Outer space, also simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace (and ... > more -
Geosynchronous orbit
A geosynchronous orbit is a geocentric orbit that has the same orbital period as the sidereal rotation period of the Earth. It has a semi-major axis of 42,164 km (26,200 miles). In the special case ... > more -
Solar radiation
Solar radiation is radiant energy emitted by the sun, particularly electromagnetic energy. About half of the radiation is in the visible short-wave part of the electromagnetic spectrum. The other ... > more -
Solar eclipse
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partially obscuring Earth's view of the Sun. This configuration can only occur during a New Moon, when the ... > more
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