Big telescopes

On the ground and in space, a global family of giant telescopes is gathering visible and invisible light from across the cosmos.

A rainbow is the spectrum of colours that make up visible light, but there are other types of light that our eyes cannot see. The full range of light is called the electromagnetic spectrum. Each research telescope is designed to detect light from a specific part of this spectrum, helping astronomers to understand more about the story of the universe.

For example, the radiation left over from the Big Bang, known as the cosmic microwave background, is detected by radio telescopes. Hundreds of exoplanets have been discovered using telescopes detecting visible and infrared light. We know black holes exist because x-ray telescopes see the material around the edges of them.

Find out more about an extremely large telescope (YouTube).

Learn about the Gaia satellite and why it’s important (YouTube).

All light travels as waves, from long radio waves to short X-rays. The earth’s atmosphere blocks some of the wavelengths and lets others pass through. That is why we have some telescopes on the ground and others in space.

Find out more about real telescopes and observatories:

Astronomers learning about the universe need telescopes that capture different parts of the electromagnetic spectrum. Using just one wavelength would exclude large parts of the information available to us, rather like watching the 4K ultra high definition version of a film on an old black-and-white television with the sound off.

As well as building different types of telescopes, we’re also pushing the boundaries on sensitivity, pixel count and speed for the detectors, so that new facilities are built with a ‘state of the art’ view of what’s beyond our atmosphere.

The cool universe

The Atacama Large Millimetre/sub-millimetre array (ALMA) came into full operation in March 2013. In the high-altitude Atacama desert 66 dishes give ALMA an effective diameter of 16 kilometres.

STFC provided equipment and software to help ALMA probe the mysteries of the early universe (just after the Big Bang), and UK industry secured over £5 million of contracts during the construction phase.

ALMA gives us an extremely clear view of the enigmatic cold regions of the universe, including the relic radiation left by the Big Bang, and to see beyond obscuring dust to the earliest and most distant galaxies.

The visible universe

The Gaia spacecraft launched in December 2013. It combines two optical telescopes with a 1 gigapixel digital camera, and its mission is to make a highly detailed 3D map of the Milky Way.

It generates images of over a billion stars, brown dwarfs and exoplanets. Looking at each object multiple times also shows us their motion and any changes in their brightness, building a three-dimensional map of our galaxy.

Gaia is expected to find hundreds of thousands of new objects in our galaxy, and is also taking a look at around 500,000 distant quasars. This data will be used to put Einstein’s general theory of relativity to the test.

About the Gaia mission.

The hot universe

The James Webb Space Telescope (JWST) successfully launched in December 2021. STFC supported and led the construction of the Mid-Infrared Instrument (MIRI). This instrument will play a key role in the telescope’s mission to look for the first galaxies that ever formed, and to search for signs of extraterrestrial life on distant exoplanets.

Using infrared allows us to see warm objects hidden behind dust clouds, such as the first stars formed in the universe, and stars that are in the process of forming planets. STFC have developed a range of resources to support public engagement with JWST.

The Very Large Telescope (VLT) at the ESO Paranal Observatory in Chile has four unit telescopes with 8.2 metre diameter mirrors, plus four 1.8 metre movable auxiliary telescopes. The telescopes can be used individually, or combined into a giant interferometer.

The VLT helps to make ESO one of the world’s most productive observatories, looking at the faintest and most remote objects in the universe. For example, it took the first image of an extrasolar planet.

UK astronomers can access the VLT via our ESO membership, and STFC supported construction of the KMOS (K-band Multi-object Spectrometer).

And we’re planning for the future with the European Extremely Large Telescope (E-ELT), which began construction in 2014 and is expected to come into operation in 2025.

The E-ELT will have a mirror 39 metres in diameter, making it the largest optical and near-infrared telescope in the world. It will be able to capture 13 times more light than the largest optical telescopes have at the moment, and generate images 16 times sharper than those produced by the Hubble Space Telescope.

Wider benefits

All of this star-gazing doesn’t only give us a good view of the universe, telescope technology brings everyday benefits here on Earth as well.

High-performance optical and infrared detectors have a wide range of applications, including biomedical imaging and security scanning.

Techniques developed to process the vast amounts of data from telescopes are being used to stabilise MRI images of moving patients. This means young children can be scanned without being sedated.

And if it weren’t for telescopes, you probably wouldn’t be reading this web page. WiFi originated in the search for radio signals from exploding black holes!

Astronomy has a big, bright future, now that we can see the universe in all its light.

Last updated: 27 July 2023

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