The James Webb Space Telescope (JWST) comes up a lot when we talk about the very boundaries of our understanding of the cosmos. For more than a quarter century, the Hubble Space Telescope has been our best window to the wider universe, but it can only do so much. The JWST is the next step, and NASA has announced that is has completed construction of the telescope and it’s on track to launch in just under two years.
The journey to this point was almost derailed a few times. The JWST was an expensive project at its inception, with an estimated budget of $5 billion. A series of delays and technical issues nearly resulted in the cancellation of the JWST in the 2012 US federal budget. Luckily, the project survived and is now back on track. However, the cost did end up ballooning to about $8.5 billion. By comparison, Hubble cost $2.5 billion.
This new telescope was designed the far surpass Hubble’s capabilities. If you’ve seen even a few of the stunning images from Hubble or seen how often its data is cited in scientific studies, that should excite you. For starters, the JWST has much larger reflecting mirrors – a total area of 270 square feet composed of 18 hexagonal beryllium coated mirrors. Hubble’s mirror has an area of just 48 square feet. This means the Webb Telescope will be able to see much fainter objects than Hubble.
The most significant improvement over Hubble is that the JWST has been designed to see far into the infrared, which Hubble can’t do very well. Hubble is just too warm to accurately scan the infrared. Anything emitting heat shines brightly in infrared, so the JWST has been designed to run extremely cool, as close to absolute zero as possible. It will be positioned at the L2 Lagrange Point. This point of orbital equilibrium will keep the Earth between the telescope and the sun, thus blocking all its infrared interference.
With an eye toward the infrared, the JWST will be able to peer through dust and gas to see the previously unseeable. It could also spot objects at extreme distances (and thus, from the distant past). You know how we always lament our inability to actually image nearby exoplanets? The Webb Telescope might be able to change that, too.
NASA is currently running tests on the telescope to ensure it’s ready for action. After that, it will be packaged up in preparation for the October 2018 launch aboard a European Ariane 5 rocket.