With its six-meter aperture, the James Webb is the largest telescope ever launched into space and, from its vantage point millions of miles from Earth, is expected to provide the best, most detailed views of the universe we’ve ever seen
This article by Martin Barstow, University of Leicester, originally appeared on Conversation and is republished here with permission.
After decades of development and many trials and disappointments along the way, the James Webb Telescope has finally begun to deliver what it came for. On July 12, NASA released the first scientific observations made by the suite of instruments aboard the mission, marking what we eagerly anticipate will be the start of a new era in astronomy.
After the spectacular Christmas launch, a series of critical deployments followed to open the telescope and its canopy. If any of these operations had failed, James Webb would have been an unusable disaster. But the program was perfectly executed, a process that went more smoothly and successfully than any of us dared to hope, let alone expect.
This is not just a testament to the skill of the engineers, technicians and scientists on the project. It also emphasizes the enormous importance of the testing program conducted on Earth to verify procedures and which sometimes reveals problems that need to be corrected before launch. Although this sometimes led to schedule slippages and cost overruns, in the end a perfect telescope was created.
In July, the telescope moved from its inspection and testing phase to operation, the amazing observatory it was long planned to be. Those of us who have been on the journey and will be working on the data can’t wait.
Clear images
The new “Early Release Observations”, selected by an international panel of representatives from NASA, ESA (European Space Agency), CSA (Canadian Space Agency) and the Space Telescope Science Institute, are part of a program designed to highlight the wide range of science, which the telescope will perform.
It is very exciting to see the new images – I was not prepared for the level of clarity and fine detail that can be seen. It’s great to finally have such high quality data.
Unveiled by US President Joe Biden, the stunning image of SMACS 0723, a cluster of thousands of galaxies, was released on July 11. The massive groups of galaxies in the foreground magnify and distort the light of objects behind them, helping us peer back in time at very faint objects.
The image shows the galaxy cluster as it looked 4.6 billion years ago. But the more distant galaxies in the image (the ones that look stretched out) are about 13 billion years old – and we already have more data on them than on any other ancient galaxy.
Images like this will help us understand how the first stars and galaxies formed. Some of them may be among the most distant known objects since the beginning of the universe. The picture is a composite “color” image made from observations made at different wavelengths. It was captured by the telescope’s Near Infrared Camera (NIRCam).
James Webb has also glimpsed the Stefan Quintet, a group of five galaxies that merge about 290 million light-years away in the constellation Pegasus. The image also suggests that there is a supermassive black hole at the center and shows the birth of stars. The data will tell us more about how galaxies evolve and the rate at which supermassive black holes grow.
The next photo shows the Carina Nebula, seen in the image below, which is one of the largest and brightest nebulae (clouds of dust and gas in which stars are born). James Webb can probe dust deep into the infrared to reveal the interior of a star’s nursery – which we’ve never seen before – to discover more about how stars are born.
The Carina Nebula is located approximately 7,600 light-years away in the southern constellation Carina. The image shows hundreds of completely new stars (each point of light is a star) and the jets and bubbles created by them. We can also see details that we cannot yet explain.
The next spectacular image is of the South Ring Nebula, or “Eight Flare,” a planetary nebula that is an expanding cloud of gas surrounding a dying star, or in this case, two dying stars orbiting each other. It is nearly half a light-year in diameter and is located about 2,000 light-years from Earth.
The frothy orange shell in the image is molecular hydrogen (a gas that forms when two hydrogen atoms bond together), while the blue center is an electrically charged gas. In the right image you can see the two dying stars in the center, giving us the opportunity to study stellar death in unprecedented detail.
The new data is the result of months of painstaking measurement and testing to make James Webb ready for use as a post-deployment science instrument. The first steps were to focus and align the images of each of the mirror segments. Each of the telescope’s science instruments – NIRCam, the Near Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI) – were also switched on and tested.
All of these instruments, which look at deep space at different wavelengths, had to be cooled, along with the telescope, otherwise they would emit background heat that would interfere with sensitive observations of astronomical objects. The last one included was MIRI, which operated at the lowest temperature, just seven degrees above absolute zero, which took several months to achieve.
The size of the telescope – its aperture – is the key thing that determines the final quality of the images and the detail that can be observed. Bigger is better. Large telescopes with apertures up to ten meters in diameter have been constructed on the ground.
However, the disturbing effects of the atmosphere, which interfere with the light reaching the telescope, make it difficult to achieve the ultimate resolution. Also, on Earth, the background light from the night sky limits the telescope’s sensitivity, the faintest objects we can see.
With its six-meter aperture, the James Webb is the largest telescope ever launched into space, and from its vantage point millions of miles from Earth, free of Earth’s atmosphere, it is expected to provide the best, most detailed views of the universe we’ve ever had seen There is no doubt that it will revolutionize our understanding of space, just as its predecessor, the Hubble Space Telescope, once did.
Martin Barstow, Professor of Astrophysics and Space Sciences, University of Leicester
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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