Hubble Space Telescope

The first major optical telescope in space, NASA’s Hubble Space Telescope is most famous for the iconic and beautiful images it has brought us of distant galaxies.

Hubble’s launch in 1990 was motivated by the idea that the best view of space is from space itself. Astronomers attempting to get a good view of very distant objects in the universe have problems doing that from Earth’s surface, thanks to obstructions from clouds, light pollution and the distorting effects of the atmosphere. Building big telescopes on mountain tops is one solution, but Hubble offers an even better view.

Named after Edwin Hubble, the US astronomer who in the 1920s showed through observations of distant galaxies that the universe was expanding, Hubble’s main light-collecting mirror is 2.4 metres in diameter (by comparison, the current largest optical telescope on Earth’s surface, the Gran Telescopio Canarias on La Palma in the Canary Islands is 10.4 metres in diameter). It observes in the visible, infrared and ultraviolet regions of the electromagnetic spectrum.

The observations it has made have increased our knowledge across the breadth of astronomy and cosmology. It has for example allowed us to pin down the expansion history of the universe better than ever before, including how it started in a big bang 13.8 billion years ago and has recently begun to expand ever-faster thanks to the influence of a mysterious “dark energy”. It has also shown that most, if not all, mature galaxies have black holes at their centres, and made key observations of distant outer-solar system bodies such as Pluto and Eris.

Hubble was last serviced back in 2009, and following the end of NASA’s space-shuttle mission in 2011 it seems unlikely there will be another crewed servicing mission going there any time soon. Nevertheless, it looks in good nick, and could last well into the 2020s and perhaps beyond. And from 2021 onwards, it’s planned that Hubble should have company, with the launch of the even-bigger James Webb Space Telescope with a 6.5-metre diameter primary mirror. Richard Webb