On Christmas Day last year, 30 years after its conception, the James Webb space telescope launched from French Guiana. On 28 December, it went past the moon. On 24 January, it fired its thrusters for five minutes and settled into its final orbit about 1,500,000 km from Earth. On 12 July, after months of painstaking setup, it produced its first image – showing us, for the first time, faraway galaxies as they were more than 13bn years ago.
The Webb telescope has been adding to this miraculous beginning ever since. Now it’s brought us something a little closer to home, a mere 615 million km away: the most extraordinarily detailed images of Jupiter we’ve ever seen.
Oxford University astrophysicist Dr Becky Smethurst, author of a forthcoming book, A Brief History of Black Holes, said that there were many reasons to be sceptical that it would ever get this far. “There were 344 single points of failure where if any tiny thing had gone wrong, the whole mission would have been scrapped. It was months of anxiety,” she said.
One major source of uncertainty after the satellite launched was how closely it would hew to its intended trajectory – with any inaccuracy bringing with it the need to burn valuable fuel. “But it was perfect. We were promised five years of data, and instead we’re going to get 20. It’s just incredible.”
Here are some of the images this impeccably directed telescope has produced – and what they show about how it operates, and the universe itself.
Webb’s First Deep Field
The first of the Webb images to be revealed – by Joe Biden – shows a galaxy cluster known as SMACS 0723. The entire picture covers thousands of galaxies in an area of the sky equivalent to a single grain of rice held at arm’s length on the surface of the Earth. “We can see things in this tiny, tiny patch in way more detail than we’ve ever been able to with Hubble [the most powerful telescope until now],” Smethurst said. “It suggests there’s no blank sky any more – everywhere you look, you’re going to find something in the background.”
Like all of the images produced by Webb, what you can see here is not visible light – but signals in the infrared spectrum captured by the satellite in monochrome, sent back to Earth as ones and zeros, and then reconstructed. The different colours don’t denote literal shades, but the wavelengths of the signals, which tell us how hot the source was. Colouring the images like this makes it easier for scientists to detect areas for further study (and generates more public excitement than a black-and-white picture ever could).
In this image, the sharp, gleaming star at the centre is in our own galaxy. The fuzzy white dots below it are whole galaxies in the SMACS 0723 cluster, shown as they were 4.6bn years ago. Better still, this cluster in the centre acts as a kind of magnifying lens for other galaxies which are much further away – as much as 13bn light years, almost back to the dawn of the universe. Because they are distorted in the process, they show as the arcs streaking across the image: red objects are caked in cosmic dust – a crucial ingredient of star formation – while green ones are full of hydrocarbons.
The Carina Nebula
The comparison of this image of a nebula – a vast cloud of dust and gas studded with stars – to the equivalent area captured by Hubble is evidence of how much more powerful Webb is. “The Carina Nebula is in our own galaxy,” Smethurst said. “Although I think it looks a bit like the Lake District here. The value of this image is really in what is shows us about the benefit of looking at relatively nearby things in infrared.
“It allows you to pierce through the dust – these little molecules of heavier elements like oxygen and carbon which scatter visible light so that you can’t see the stars that have formed. In this picture, we get through that dust to the three dimensional structure of the nebula.”
Stephan’s Quintet
This image, constructed from more than 150m pixels sent by Webb, shows a group of galaxies in the Pegasus constellation, and provides scientists with the means to see how their interaction triggers the formation of stars. “This is my favourite, because it’s directly relevant to my work,” said Smethurst. “It shows four galaxies interacting, one of them with a growing black hole, and one which isn’t. What’s amazing is that if you zoom in you can see individual stars: until now we’ve barely been able to do that with our closest galaxy, Andromeda, and these are much more distant.”
The galaxy to the left of the formation is closer than the others – 40m light years away as opposed to 290m. The topmost swirl in the image contains a black hole 24m times the mass of the sun. “It’s an incredibly bright source of light,” Smethurst said. “What this shows is the gas swirling around the black hole lit up in all its glory.”
WASP-96b (spectrum)
This is not an image, but “it’s still enormously exciting to astrophysicists”, Smethurst says. The set of data reveals clearly that this planet, 1,150 light years away, has the distinctive characteristics of water.
Webb measured light coming from the WASP-96 system as the planet moved across the star – and the way the gas giant has “stolen away a little bit of the starlight” as it passes through its atmosphere reveals the unique signature of water, Smethurst said.
The findings are also important because they show “what the telescope is capable of”, Smethurst said. “This is a big bright planet, very close to its star. It’s easier to observe the light passing through the atmosphere because it passes in front of the star often. Because it’s so easy here, it suggests that with the harder ones that are further away and pass in front of their star less often like Earth, you won’t be wasting your time. It’s this idea of finding ‘Earth’s twin’ – something that looks incredibly habitable for life as we know it.”
Jupiter
If the primary purpose of Webb is to tell us more about light sent by faraway stars billions of year ago, it turns out to also be able to produce stunning images of our own solar system unlike any we have seen before. “I was amazed when I saw the level of detail here – I thought it would be washed out because it’s so bright,” Smethurst said. “But it’s very clever how they’ve used different wavelengths to capture different things.”
The red haze at the planet’s north and south poles are auroras – created by the interaction of particles from the sun with the planet’s magnetic field. The famous Great Red Spot, a storm so big it could swallow Earth, appears in white because it reflects so much sunlight. “And the darker areas reveal the areas where the light has pierced further into the atmosphere,” Smethurst said.
Valuable though Webb’s observations will be for scientists, images like this also strike Smethurst as important for their sheer, universal beauty. “Everyone is curious about the world we live in,” she said.
