30 years of Hubble: a celebration

Written by Callum Murison

Today marks the 30th anniversary of the launch of the Hubble Space Telescope – one of the most important and recognisable successes in the history of astronomy. A credit to some of the amazing engineers who oversaw its construction, Hubble has allowed us to see wonders well beyond the confines of the Solar System and greatly enhance our picture of the Universe.

Named after early-20th century astronomer Edwin Hubble (who will be all too familiar to those using Hubble’s Law in Higher physics!), the telescope was initially meant to be launched in 1983, but delays to construction, followed by the tragic Challenger disaster in 1986, meant that the eventual launch date was April 24th 1990.

The Hubble Space Telescope

So, why was a space telescope so important if we already had telescopes at ground level, with larger mirrors, which were easier to operate and service? Well, it all comes down to the Earth’s atmosphere, causing two main issues. Firstly, the ‘turbulence’ and gases within distort the image captured and result in stars twinkling when seen from the Earth’s surface. Secondly, the aforementioned gases strongly absorb the light emitted by interstellar objects beyond the visible spectrum – specifically infrared (IR) and ultraviolet (UV) light. Hubble, therefore, allows us to both view a much larger range of light, whilst also allowing us to form clearer images.

However, when Hubble was finally launched in 1990, there was a problem. A big one. A telescope is only as good as its mirror, and Hubble’s primary mirror had a tiny defect. A slight miscalibration in equipment during mirror construction (over 10 years before the launch) meant that the curvature of the mirror was very slightly ‘off’. But this error of just 2 microns (just 1/50th of the width of a human hair) meant that the images initially returned by Hubble were blurry – due to spherical aberration. NASA quickly determined (perhaps unsurprisingly!) that replacing the entire primary mirror was not feasible, so instead decided to remedy the problem through designing and building COSTAR (the Corrective Optics Space Telescope Axial Replacement). NASA describes this as like using “a pair of glasses to correct the vision of a near-sighted person.” COSTAR was successfully installed by Space Shuttle Endeavour in December 1993.

Spherical aberration – the outer rays are refracted more than those at the centre, meaning they don’t all intersect nicely at a focal point

Thankfully, the pictures returned by Hubble beyond this installation were clear, and it could begin exploring the cosmos in more detail. It has discovered countless exoplanets, supermassive black holes, the moons of Pluto, and helped to create a 3D map of dark matter in the Universe – and that’s just naming a few! To put things into perspective, in 2011, Hubble made its millionth observation, and the year also saw the 10,000th paper published using data collected by the telescope.

Since its launch, Hubble has proved hugely effective in identifying new facts about the Universe. Despite its ‘replacement’ (the James Webb Space Telescope) due to be launched next year, Hubble is still operational and will continue alongside the JWST in photographing and exploring space – it could continue until 2030-2040. And at this point, I am simply going to stop writing, and instead let some of the beautiful pictures captured by the world’s most famous space telescope do the talking. Happy birthday Hubble!

Crab Nebula
An image of Saturn taken in 2019
Galaxy cluster MACS J0416.1-2403
Serpens Nebula HBC 672

Hubble-captured images produced primarily by NASA, ESA and the Space Telescope Science Institute (STScI). The website in which I found these images can be found by clicking here.

Additional credit to the Infrared Processing and Analysis Center (IPAC), University of California, Berkeley and the University of New South Wales.

About the author

Callum Murison

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