GoKawiilLast September, JWST took this image of a protostellar jet at the outskirts of the Milky Way. From tip to tip, the jet spans about double the distance from the Sun to its closest neighbouring star system, α Centauri.Credit: NASA, ESA, CSA, STScI, Yu Cheng (NAOJ); Image Processing: Joseph DePasquale (STScI)
From black holes in the early Universe1 to atmospheres cloaking distant planets2, the James Webb Space Telescope (JWST) studies cosmic phenomena that no other observatory has been able to probe. The most powerful infrared telescope ever built, it released its first images four years ago this week.
‘It’s a dream’: JWST spies more black holes than astronomers predicted
Its success is a tribute to the talent and hard work of its scientists and engineers. Conceived in 1989, it is also testament to persistence, often against the odds — more than once, the telescope faced cancellation as its costs ballooned, eventually reaching US$10 billion for construction and the first five years of operation.
With four years under its belt, JWST has just one more year of prime-mission operations before NASA must approve an extension. The agency is also considering whether and how to end another flagship observatory: the Hubble Space Telescope. Hubble observes mostly in optical and ultraviolet wavelengths and has reshaped astronomers’ understanding of how stars and galaxies are born, evolve and die.
There is much science still to do with both telescopes, and both must be renewed. Hubble costs around $98 million to operate each year, and JWST around $200 million. These are small numbers given the immense scientific return. The telescopes complement one another beautifully: to not renew them would be like building a transformative AI technology and then disconnecting it from the Internet so it couldn’t be used.
A 50-year-old full-scale mock-up of the Hubble Space Telescope went on display last month at the Smithsonian National Air and Space Museum in Washington DC.Credit: Shannon Finney/Getty
As an infrared telescope, JWST observes wavelengths at the redder end of the electromagnetic spectrum. Because the expansion of the Universe shifts light toward the red, JWST has an unprecedented view of the most distant realms of the cosmos, where objects appear as they did not long after the Universe was born in the Big Bang, 13.8 billion years ago. This view is thanks in no small part to a large number of features constructed through engineering and technological firsts, from the 6.5-metre-wide, foldable primary mirror to a tennis-court-sized sunshield.
Among its discoveries, JWST has spotted small, distant black holes, the existence of which challenges ideas about how black holes form. It has found some of the farthest galaxies observed, including star systems that are bigger and brighter than astronomers would have expected in the early Universe. Closer to home, JWST discovered a lava world with an improbably wet atmosphere; peered through dusty disks at planets being born; and measured the chemical composition of an interstellar visitor, the comet 3I/ATLAS, which swooped past the Sun late last year3.
First images from world’s largest digital camera leave astronomers in awe
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