‘Cosmic time machines’: how space telescopes transformed our ability to understand the universe

The launch of Hubble in 1990 marked a turning point in our quest to unravel the mysteries of deep space

If you’ve ever been blown away by an image of outer space, it’s a pretty safe bet it was taken by a spacecraft. That’s no surprise if we’re talking about the planets of our own solar system, where probes have been sending back spectacular closeups since the 1960s. But what about all those nebulae, star clusters and galaxies that are much farther away? For stunning astrophotography, nothing can beat Nasa’s Hubble space telescope, or its huge new successor, the James Webb space telescope (JWST). They’re called space telescopes not just because they observe space, but because they’re located in space.

The JWST, for example, is about 930,000 miles (1.5m kilometres) away – approximately four times as far as the moon and far enough that radio signals sent from Earth, travelling at the speed of light, take about five seconds to reach it. In other words, the JWST is about five light seconds away from Earth. But many of the galaxies it has photographed are hundreds of millions, or even billions, of light years away. Clearly, the reason for locating the JWST, and Hubble before it, in space has nothing to do with getting closeup pictures. They’re no nearer to the objects they’re viewing than telescopes here on Earth. So why do astronomers go to all the trouble and expense of putting telescopes in space?