What’s the difference between the Hubble and James Webb telescopes?

The James Webb Space Telescope will have an approximately 6.5 meter diameter primary mirror, which would give it a significantly larger collecting area than the mirrors available on the current generation of space telescopes. The Hubble Telescope mirror is a much smaller 2.4 meters in diameter. Credit: NASA.

NASA, ESA and the Canadian Space Agency prefer that people think of the James Webb Space Telescope (JWST) as the successor to the Hubble Space Telescope, not its replacement. Why is that, and what’s the difference between the two?

While the JWST is much larger in size, its mission and capabilities are slightly different. As well, let’s not forget that even when it is commissioned six months after launch, that the Hubble telescope will still be continuing its mission.

The James Webb Space Telescope will orbit the sun 1.5 million kilometres (1 million miles) away from the Earth at what is called the second Lagrange point or L2. (Note that these graphics are not to scale.) Credit: NASA.
The James Webb Space Telescope will orbit the sun 1.5 million kilometres (1 million miles) away from the Earth at what is called the second Lagrange point or L2. (Note that these graphics are not to scale.) Credit: NASA.

Here’s the short answer from NASA on the basic differences between the telescopes.

“Hubble’s science pushed us to look to longer wavelengths to ‘go beyond’ what Hubble has already done. In particular, more distant objects are more highly redshifted, and their light is pushed from the UV and optical into the near-infrared. Thus observations of these distant objects (like the first galaxies formed in the Universe, for example) requires an infrared telescope.”

Earth’s Lagrange points. As the Earth orbits the Sun, the Webb telescope will orbit with it – but stay fixed in the same spot, L2, with relation to the Earth and the Sun.

“This is the other reason that Webb is not a replacement for Hubble; its capabilities are not identical. Webb will primarily look at the Universe in the infrared, while Hubble studies it primarily at optical and ultraviolet wavelengths (though it has some infrared capability). Webb also has a much bigger mirror than Hubble. This larger light collecting area means that Webb can peer farther back into time than Hubble is capable of doing. Hubble is in a very close orbit around the earth, while Webb will be 1.5 million kilometers (km) away at the second Lagrange (L2) point.”

The Canadian Space Agency has also chipped in with its own explanation in the following YouTube video.

About Marc Boucher

Boucher is an entrepreneur, writer, editor & publisher. He is the founder of SpaceQ Media Inc. and CEO and co-founder of SpaceRef Interactive LLC. Boucher has 20 years working in various roles in the space industry and a total of 30 years as a technology entrepreneur including creating Maple Square, Canada's first internet directory and search engine.

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