Hubble vs JWST Telescope – What’s the difference?

September 13, 2023

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Space contains some of the most fascinating and exotic objects ever studied! From black holes to pulsars, exoplanets to supernovas, the cosmos is teeming with bodies which stretch our imaginations and our understanding of how the universe works. For the past 30 years or so, many of the most incredible discoveries humankind has made have come from the Hubble Space Telescope.

In this blog we look at the key differences between these two magnificent telescopes and discover how they both play an incredibly important part in research.

About Hubble

Hubble’s track record is impressive. In 1994, Hubble provided conclusive evidence of the existence of supermassive black holes at the centres of galaxies by observing the galaxy M87. In 2001, Hubble measured the elements in the atmosphere of exoplanet 209458b – the first planetary atmosphere outside the Solar System to be detected. And in 2010, Hubble photographed never-before-seen evidence of a collision between two asteroids.

And Hubble still has plenty left to give. Despite being operational for over three decades and having a relatively modest 2.4m mirror, demand for its use in research still exceeds available observing time. It remains unbeaten in its ability to observe the universe at the optical and ultraviolet wavelengths.

A large part of its success comes from the fact that it is in space. This gives Hubble two distinct advantages over bigger 8-10m Earth-based telescopes. Firstly, it means that Hubble can capture observations without being affected by the air currents that appear to make stars twinkle from the ground. And secondly, it can observe in the ultraviolet wavelength – which is all but impossible from the ground given the presence of gases such as ozone in the atmosphere, which blocks ultraviolet light.

About JWST

While these advantages mean Hubble still has at least ten to twenty more years before it’s retired, plans for the next generation of space telescope began as long ago as 1996. Decades of work were put in, culminating in the launch – on Christmas Day 2021 – of the James Webb Space Telescope (JWST). A combined project with the European Space Agency and the Canadian Space Agency, JWST has enough fuel to last at least the next ten years.

Early observations from JWST have been spectacular. There’s a continued focus on exoplanets with observations of the atmospheric composition of the hot gas giant WASP-96b. There are images of enormous gas clouds which are the nurseries in which new stars are born. And there are observations of the composition of very distant galaxies, some 13.1 billion light-years away. And this is in the first few months of observation time.

So, how is JWST different from Hubble?

JWST is different from Hubble in several key ways. For a start, JWST’s mirror is 6.5m in size – two and a half times bigger than Hubble’s. Hubble is in a near-Earth orbit, whereas JWST is 1.5 million kilometres away. And JWST observes at the infrared end of the electromagnetic spectrum, whereas Hubble primarily observes the visible and ultraviolet.

It is this focus on the infrared which really differentiates the two. A core part of JWST’s mission is to look at some of the most distant galaxies in the universe. More distant objects are more highly red-shifted and their light is moved from the ultraviolet and optical to the infrared. Combined with its bigger mirror, this means JWST will be able to peer further back in time than Hubble and help to answer more questions about the early universe.

visible and infrared comparison of ngc 2174

If you want to learn more about some of the fascinating objects mentioned in this blog, then sign up to Mission Astro today! With 32 sessions covering a range of objects and phenomena observed across the Milky Way, you’re sure to learn so much about the cosmos.

We even have a free taster session on supermassive black holes and the stars that fall into them! If you have any questions, please email course leader, Dr Sarah Crick, at [email protected]
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