Why was the JWST Built?

The mission began in 1996 as the Space Telescope Science Institute began investigating the feasibility of constructing a large infrared telescope as a successor to Hubble. The JWST can observe more distant objects than Hubble because those objects are highly redshifted and thus their light is emitted in the near-infrared part of the spectrum. The JWST also has different capabilities than Hubble which allows it to study these much more distant objects, JWST has a much larger mirror and is 1.5 million kilometres away from the Earth at the second Lagrange point (L2). The L2 is a point at which the gravitational forces of the Earth and Sun are balanced and thus a spacecraft can “hover in place”.

The Construction of the JWST

The construction of the JWST began in 2004 with the science instruments and the 18-segment primary mirror being the first components to be built. In 2008, the mission passed important design reviews and thus construction on the other vital components of the telescope could begin. The mirrors were completed in 2011, these mirrors are made of gold-coated beryllium and are the most visually striking element of the JWST. In 2012 and 2013, the constructed science instruments and other important structures were delivered to the Goddard Space Flight Centre in the US so that the assembly of the various parts of the telescope could begin. The main science instruments of the JWST are the mid-infrared instrument (MIRI) and the near-infrared camera (NIRCam). The manufacture of the spacecraft parts began in 2014. From that year on, telescope assembly and testing were mainly what was carried out to get JWST launch ready. Then, on December 25^th, 2021, the JWST was launched on an Ariane 5 rocket and began its month-long journey to L2.

Important Scientific Discoveries Made by the JWST

In the couple of years since, even though we are still only at the beginning of Webb’s lifetime, (there is fuel for 26 years of JWST’s telescope operations due to its excellent insertion by the Ariane 5) there have been numerous fantastic observations and scientific discoveries made by Webb.

One of the first exciting observations from the JWST was its first Deep Field. This was the first image delivered by Webb and is the deepest infrared image of the Universe so far. It is an image of the galaxy cluster SMACS 0723. The image was taken by NIRCam and is a composite of images of different wavelengths that took only 12.5 hours demonstrating the JWST’s superior capabilities over its predecessors. This image reveals thousands of galaxies all which lie in a patch of sky that covers what a grain of salt held at arm’s length would! The NIRCam has brought these galaxies into sharp focus with structures that have never been seen before now able to be studied. Researchers will be able to use this deep field image to discover more about how the galaxies were formed, their masses and ages, as well as their compositions.

The JWST has observed the oldest and most distant galaxies ever detected. The oldest of these formed only 320 million years after the Big Bang when the Universe was still very young. While 320 million years may sound like a very long time, it is only 2% of the current age of the Universe which is over 13 billion years. The discovery of galaxies that formed so close to the start of the Universe is very exciting for astronomers as it helps to deepen understanding around the early universe and gives us an insight into how galaxy formation happened so close to the Big Bang.

Another important discovery made by Webb was the detection of CO₂ on an exoplanet atmosphere for the first time. The planet (WASP-39 b) is a gas giant that is orbiting a Sun-like star 700 light-years away. WASP-39 b was discovered in 2011 using the transit method which is where a planet is detected based on the periodic dimming of the host star as the planet orbits it. The near-infrared spectrograph (NIRSpec) was the instrument used to detect the carbon dioxide on the exoplanet. This was an important discovery as understanding the composition of exoplanets can give astronomers a lot of information on the origin of the planet and its formation.

The Future of the JWST

The future of the JWST is bright based on the important scientific discoveries that have been made in the short few years it has been operational so far. Many more important astronomical discoveries will be made during its lifetime with many exciting proposals that avail of JWST observation time from various scientists across the globe that have been accepted. Having a process that allows the wider scientific community to propose ideas for research using the JWST means that there is a wide variety of diverse subjects that will be researched by Webb and hopefully that will greatly expand our understanding of the Universe. I myself am really looking forward to seeing the results that come from the JWST’s observations in the coming years!

Image and Information Sources

The sources for the information and images contained in this blog:

1. JWST Mission Timeline: https://webbtelescope.org/webb-science/the-observatory/mission-timeline#:~:text=Construction%20on%20Webb%20began%20in,testing%20to%20meet%20required%20specifications.
2. Webb vs Hubble Telescope: https://www.jwst.nasa.gov/content/about/comparisonWebbVsHubble.html
3. Webb delivers deepest infrared image of universe yet: https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet
4. JWST discovers oldest galaxies ever observed: https://phys.org/news/2023-04-webb-telescope-oldest-galaxies.html#:~:text=The%20Webb%20telescope%20also%20confirmed,by%20the%20Hubble%20Space%20Telescope.
5. JWST detects carbon dioxide in exoplanet atmosphere: https://www.nasa.gov/feature/goddard/2022/nasa-s-webb-detects-carbon-dioxide-in-exoplanet-atmosphere
6. Featured Image: Artist conception of the James Webb Space Telescope – credit: NASA GSFC/CIL/Adriana Manrique Gutierrez. https://www.flickr.com/photos/nasawebbtelescope/51412123217/in/album-72157624413830771/
7. JWST Deep Field Image: Webb’s First Deep Field Image (NIRCam Image) – credit: NASA, ESA, CSA, STScI. https://webbtelescope.org/contents/media/images/2022/035/01G7DCWB7137MYJ05CSH1Q5Z1Z
8. JWST oldest galaxies spectra: Webb Spectra Reach New Milestone in Redshift Frontier – credit: NASA, ESA, CSA, M. Zamani (ESA/Webb), Leah Hustak (STScI). https://webbtelescope.org/contents/media/images/01GKRX20YPY9XSXRWX31H57P2A?Type=Spectra&Category=03-galaxies&page=1&keyword=galaxy
9. JWST carbon dioxide spectra: Exoplanet WASP-39 b (NIRSpec Transit Light Curves) – credit: NASA, ESA, CSA, Leah Hustak (STScI), Joseph Olmsted (STScI) https://webbtelescope.org/contents/media/images/2022/042/01GB31JJZT8NSEZQCJ8BE5EY56?news=true