Outer space is the region beyond Earth's atmosphere.
It is a near-perfect 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 of outer space, as set by the
background radiation from the Big Bang, is 2.7 kelvins (−270 °C; −455 °F).
Outer space is the closest known approximation to a perfect vacuum.
It has effectively no friction, allowing stars, planets, and moons to move freely
along their ideal orbits, following the initial formation stage.