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Outer space

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 between celestial bodies. 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, at 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.

Humans began the physical exploration of space during the 20th century with the advent of high-altitude balloon flights, followed by manned rocket launches. Earth orbit was first achieved by Yuri Gagarin of the Soviet Union in 1961, and unmanned spacecraft have since reached all of the known planets in the Solar System. Due to the high cost of getting into space, manned spaceflight has been limited to low Earth orbit and the Moon.

Outer space represents a challenging environment for human exploration because of the dual hazards of vacuum and radiation. Microgravity also has a negative effect on human physiology that causes both muscle atrophy and bone loss. In addition to these health and environmental issues, the economic cost of putting objects, including humans, into space is very high.

Selected article

The Apollo 8 crew portrait

Apollo 8 was the second manned mission of the Apollo space program. Commander Frank Borman, Command Module Pilot James Lovell and Lunar Module Pilot William Anders became the first humans to travel beyond Earth orbit and into an orbit around the Moon. It was also the first manned launch of the Saturn V rocket. NASA prepared for the mission in only four months. The hardware involved had only been used a few times—the Saturn V had only launched twice before, and the Apollo spacecraft had only just finished its first manned mission, Apollo 7. However the success of the mission paved the way for the successful completion of John F. Kennedy's goal of landing on the Moon before the end of the decade. After launching on December 21, 1968, the crew took three days to travel to the Moon, which they orbited for twenty hours. While in lunar orbit they made a Christmas Eve television broadcast that is thought to be one of the most watched of all time.

Selected picture

Sombrero Galaxy
Credit: NASA / STScI

The Sombrero Galaxy is a spiral galaxy in the Virgo constellation. It was discovered in the late 1700s. It is about 28 million light years away and is just faint enough to be invisible to the naked eye but easily visible with small telescopes. In our sky, it is about one-fifth the diameter of the full moon. M104 is moving away from Earth at about 1,000 kilometers per second.

Space news

Wikinews Space Portal
  • May 7: NASA's InSight lander and MarCO craft launch in new mission to Mars
  • April 21: NASA launches exoplanet-hunting satellite TESS
  • April 3: China's Tiangong-1 space station crashes into Pacific
  • March 17: British scientist Stephen Hawking dies aged 76
  • January 6: Mysterious dimming of Tabby's star likely due to space dust, not alien superstructures, say scientists
  • November 3: Astronomers report dwarf star with unexpectedly giant planet
  • September 6: Peggy Whitson, record-breaking 'American space ninja', returns to Earth
  • July 17: Sun's mood swings not so strange after all, say scientists
  • July 14: Astronomers discover smallest known star
  • June 8: Astronomers reveal discovery of the hottest gas giant exoplanet known yet
  • June 4: Curiosity Rover analysis suggests chemically complex lake once graced Mars's Gale crater
  • May 18: Simulations show planet orbiting Proxima Centauri could have liquid water

Upcoming spaceflight launches

Astronomical events

6 July, 16:47 Earth at aphelion
12 July, 05:30 Mercury at greatest eastern elongation
12 July Pluto at opposition
13 July, 03:01 New moon and partial solar eclipse
13 July, 08:18 Moon at perigee
27 July, 05:13 Mars at opposition
27 July, 05:28 Moon at apogee
27 July, 20:23 Full moon and total lunar eclipse
29 July, 00:00 Southern Delta Aquariids peak

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