spaceSpace and Physics

The James Webb Space Telescope – What’s The Big Deal?

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Charlie Haigh & Eleanor Higgs

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The JWST is the largest and most powerful telescope ever made. Launched into space on Christmas Day 2021 from Europe’s Spaceport in French Guiana, at a cost of around $10 billion dollars, the JWST can peer further back in time than any other telescope to capture the formation of stars and planets, and even the birth of the first galaxies in the early universe.

JWST stands on the shoulders of its predecessor, the Hubble Space Telescope, and while it is thought that they will work together for some years, the main difference is that Hubble uses optical and ultraviolet wavelengths. The JWST will capture much of its information in infrared. The use of infrared radiation allows the JWST to peer through gas and dust, and to view faint and distant objects more clearly than ever before.  


This immense international collaboration between NASA, the European Space Agency, and the Canadian Space Agency has been 20 years in the making. With development beginning in 1996, the initial 2007 launch date was postponed continuously for the next 14 years, leading some to doubt the voyage would ever take place. There was, however, good reason to postpone. Due to the nature of the JWST orbit, repairs would be impossible – they had to make sure it was perfect.

JWST journeyed to its final location 1.5 million kilometers (1 million miles) away over just 29 days. This super expensive bit of kit is now positioned directly behind Earth, in a gravitationally stable location known as Lagrange 2 or L2. Operating in a halo orbit, the JWST’s L2 positioning enables it to move at a relatively continuous distance from Earth, while keeping out of both the Moon and Earth’s shadows. Unlike Hubble, which orbits Earth at a distance of roughly 550 kilometers (340 miles), the JWST will be held in position by the Sun's orbit. The JWST L2 positioning also requires less fuel usage, meaning a longer mission lifetime of between five and 10 years. 

As the successor to Hubble, it does come with a few upgrades, it can even take a selfie! The JWST’s primary mirror is 6.5 meters in diameter and 25 square meters in area, that’s three times the size of the mirror used on the Hubble telescope. The five-layer sunshield doesn’t disappoint either, measuring in at the size of a tennis court. The sunshield provides the equivalent Sun Protection Factor (SPF) of a million and is imperative to the JWST’s functionality, as the telescope needs to remain cold for the infrared capacity to function correctly. 

According to NASA, the science goals for the JWST can be grouped into four themes: 

  1. 1. First Light and Reionization – the infrared capabilities of the JWST will enable it to look back over 13.5 billion years to reveal the first stars and galaxies forming in the early universe. 
  1. 2. Assembly and Galaxies – astronomers will compare the formation of early galaxies with how galaxies are assembled over billions of years. 
  1. 3. The Birth of Stars and Protoplanetary Systems – Unlike Hubble, the JWST will be able to use its infrared to look through huge clouds of space dust, hopefully revealing how stars are born. 
  1. 4. Planetary Systems and the Origins of Life – the JWST will tell us more about the atmosphere of extrasolar planets, and study objects within our Solar System too. 

The first JWST photo was released in early 2022. It shows the first photons of light captured by the telescope as it aligned its 18 mirrors to a nearby star. But before it gets going, it needs to cool down to reach its optimum operating temperature of around 40 K (less than -380°F), which will take just under 100 days from launch to reach its operational temperature. As NASA puts it, the telescope is currently “chilling out”, preparing itself to begin capturing images of a relatively unexplored universe. It is thought that the first “proper” images from the JWST will be released around six months after launch, making summer 2022 a very exciting time for the astronomy community. 


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