The James Webb Space Telescope, which is reported to be the most advanced telescope to be put into space ever, is entering its final stage of testing on Earth. It is scheduled to launch in October 2018, and is expected to help astronomers observe distant parts of the galaxy.

"This engineering marvel is designed to unravel some of the greatest mysteries of the universe, from discovering the first stars and galaxies that formed after the big bang to studying the atmospheres of planets around other stars," the agency said in a statement.

The telescope is a joint venture between the NASA, ESA (the European Space Agency) and the Canadian Space Agency. The world's most advanced space observatory will not replace the Hubble Space Telescope, but will be more like its scientific successor as their capabilities are not identical, according to Nasa.

The image above shows the "wings" of the mirror spread open inside a clean room at NASA's Johnson Space Center in Houston, where the telescope will undergo its last cryogenic test. It will be tested to see if it can sustain in below freezing temperatures in space.

The JWST will be stationed nearly 1.5 million kms from Earth at the Earth-Sun L2 (Lagrange) point. One of its main aims will be to observe targets beyond the reach of current ground and space-based instruments, including direct imaging of exoplanets.