Look up at the sky. What do you see? Apart from the many cosmic bodies that we can see through our naked eyes such as the moon, stars and the planets, it also encompasses galaxies, nebulae, black holes and so on. Now add to that the many spacecraft and satellites we put in Earth's orbit. Any man-made, artificial materials that are orbiting the Earth which is no longer operational are referred to as space debris or space junk. They just float in space in terms of their size, they can be as big as an inactive satellite or as minuscule as the paint flecks that come off a rocket. Most of the debris can be found in the Low Earth Orbit (LEO), which is less than 1000 km from the Earth's surface. At times they are also found in the geostationary orbit. The time taken by the debris to re-enter Earth's atmosphere depends upon its altitude. The "pollution" of space due to human activities has been a concern that space faring nations must address at the earliest. Space debris can endanger mankind's space explorations, by colliding with satellites in orbit and other missions. Seen here is a computer-generated image released by the European Space Agency (ESA) showing trackable objects in orbit around Earth.
Picture Credit : Google