Karl Jansky in the 1930's discovered that galaxies emitted radio waves, and with a radio telescope you can see new worlds. He was actually looking for radio interference in Trans-Atlantic communication, and discovered the reason for that but also that radio telescopes could be useful in exploring space.

Radio telescopes have reflectors and receivers and need to be large. An example of a modern radio telescope is The Very Large Array in New Mexico, composed of 27 antennas over 36 kilometers (22 miles) or the Parkes Radio Telescope in Australia (right).

Other telescopes from infrared and ultraviolet can also be used especially when placed on mountaintops or on orbiting satellites. Gamma and X-ray telescopes have also been used since the 1970's. Telescopes will keep advancing as astronomers search the Universe.