The James Webb Space Telescope is the most powerful space telescope ever built. 

Designed as the Hubble Space Telescope's successor, the Webb is twice as large as Hubble and features a spectacular 21-foot, gold-coated mirror array. The array is composed of 18 large hexagonal mirrors that will collect the telescope's infrared readings. 

According to NASA, the Webb telescope will cover longer wavelengths of light and will be more sensitive than Hubble. 

These combined features will enable scientists to look farther back in time "to see the first galaxies that formed in the early universe, and to peer inside dust clouds where stars and planetary systems are forming today."

Engineers conduct a white light inspection on NASA's James Webb Space Telescope in the clean room at NASA's Goddard Space Flight Center, Greenbelt, Maryland. (Image credit: NASA/Chris Gunn)
(Image credit: NASA/Chris Gunn)

With construction now complete, NASA will begin the final tests before its scheduled launch date in October 2018. 

The Webb telescope is a joint venture between NASA, the European Space Agency and the Canadian Space Agency.