Portal:Outer space

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The interface between the Earth's surface and outer space. The Kármán line at an altitude of 100 km (62 mi) is shown. The layers of the atmosphere are drawn to scale, whereas objects within them, such as the International Space Station, are not.

Outer space, or just space, is the expanse that exists beyond the Earth and outside of any astronomical object. Outer space is not completely empty—it is a hard vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. The baseline temperature, as set by the background radiation from the Big Bang, is 2.7 kelvins (−270.45 °C; −454.81 °F). The plasma between galaxies accounts for about half of the baryonic (ordinary) matter in the universe; it has a number density of less than one hydrogen atom per cubic metre and a temperature of millions of kelvins; local concentrations of this plasma have condensed into stars and galaxies. Studies indicate that 90% of the mass in most galaxies is in an unknown form, called dark matter, which interacts with other matter through gravitational but not electromagnetic forces. Observations suggest that the majority of the mass-energy in the observable universe is a poorly understood vacuum energy of space, which astronomers label dark energy. Intergalactic space takes up most of the volume of the Universe, but even galaxies and star systems consist almost entirely of empty space.

Outer space does not begin at a definite altitude above the Earth's surface. However, the Kármán line, an altitude of 100 km (62 mi) above sea level, is conventionally used as the start of outer space in space treaties and for aerospace records keeping. The framework for international space law was established by the Outer Space Treaty, which entered into force on 10 October 1967. This treaty precludes any claims of national sovereignty and permits all states to freely explore outer space. Despite the drafting of UN resolutions for the peaceful uses of outer space, anti-satellite weapons have been tested in Earth orbit.

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In the news

9 January 2019 –
Scientists announce through the Nature journal, the discovery of 13 deep-space fast radio bursts (FRBs), named FRB 180814, by the CHIME radio telescope in British Columbia, Canada. (BBC)
6 January 2019 – Atira asteroid
The Zwicky Transient Facility in California discovers a large Atira asteroid, 2019 AQ3, an asteroid with a diameter of 1.4 kilometres (0.87 miles) that stays closer to the Sun during its orbit than any other known asteroid, passing from inside the orbit of Mercury to just outside the orbit of Venus. (Minor Planet Center)
3 January 2019 – Chinese Lunar Exploration Program
China National Space Administration's robotic lander Chang'e 4 successfully lands at the Von Kármán lunar crater on the far side of the Moon. (BBC)
1 January 2019 – 2019 in spaceflight
New Horizons makes a flyby of Kuiper belt object 2014 MU69, nicknamed Ultima Thule, at 05:33 UTC, becoming the farthest object in the solar system visited by a spacecraft. It is a contact binary. (The New York Times)
18 December 2018 – Space policy of the Donald Trump administration
U.S. President Donald Trump signs an executive memorandum to re-establish the United States Space Command. (CNN)
13 December 2018 –
Virgin Galactic's SpaceShipTwo successfully completes its fourth powered test flight with VSS Unity and reaches space at an altitude of 82.7 km (51.4 mi) but does not breach the 100 km (62 mi) Karman Line. (BBC)


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