The writer is a science commentator
You may not be able to see it but, even in the dark, you can still feel the warmth given off by a hot object. Sir Frederick William Herschel, the German-British astronomer who discovered Uranus, first described the phenomenon in 1800 as “radiant heat”. We now know it as infrared radiation, a form of light invisible to the human eye.
Thanks to the $10bn James Webb Space Telescope, we are beginning to “see” the radiant heat of the early universe like never before. On Monday night, to the excitement of professional astronomers and amateurs the world over, President Joe Biden unveiled the telescope’s first full-colour image of deep space. The striking snapshot, taken at minimally explored wavelengths and at unprecedented resolution, reveals a cornucopia of cosmic objects including stars and spiral-armed galaxies.
The image is yet to be fully analysed but some objects are cosmic relics dating to within 0.7bn years of the Big Bang, the cataclysmic event that spawned our universe 13.8bn years ago. A new era of astronomy, in which we can finally glimpse the oldest objects in the universe and gain a fuller understanding of its origins, has officially begun.
Tuesday saw four more important results emerge from the Webb’s first week of observations. The gas giant exoplanet, WASP-96b, which orbits a distant star 1,150 light years away, was revealed to have an atmosphere containing water vapour, clouds and haze. Another image shows the death throes of a star, its expelled matter diffusing into a beautiful planetary nebula. Two of the five galaxies in Stephan’s Quintet, lying 300mn light years away, are captured in the process of merging. The last of the “reveals” is a showstopping, Hubble-style close-up landscape of the Carina Nebula, uncovering sparkling new infants in this stellar nursery.
Chris Lintott, professor of astrophysics at Oxford university and a researcher on galaxy formation, said he was blown away by the quality and beauty of the images. “It knocked my socks off,” Lintott said on Tuesday. “I was sitting in a roomful of galaxy experts when the Stephan’s Quintet image was shown, and jaws hit the floor. The Webb is going to produce some of the most iconic pictures of the space age.”
Webb’s “first deep field”, as the image of deep space released on Monday is known, is a composite picture taken over 12.5 hours, observing at different wavelengths. It shows the cotton-wool-like galaxy cluster SMACS 0723 centrally in the foreground, plus bright white stars, with their characteristic spikes. The features that have most captivated astronomers, however, are the orange, pink and red smears that seem to sketch faint arcs around the central galaxy cluster. These smears and streaks — tinted into visibility using a palette that spans the range of emitted radiation — may represent some of the oldest galaxies seen in such detail, lying farther back in space (and time) behind the cluster.
The fact that we can see them, even though they are out of direct view, is due to a phenomenon known as gravitational lensing. This can both reveal and magnify distant objects. SMAC 0723’s massive gravity bends space, causing the distant light from the galaxies behind to curve around it. The resulting smudgy blobs are likely to be magnified images of the earliest galaxies, their existence finally unmasked by a telescope capable of registering their faint light, which has stretched out on its journey across the universe from visible wavelengths to longer ones in the infrared range.
As Lintott points out, bigger light-collecting mirrors result in sharper images, of the type that Webb is now delivering. The audacious gamble on the telescope’s giant foldable mirror has paid off. It is hard to believe that the Earth-orbiting telescope, regarded as one of the most complex engineering feats ever attempted and nearly cancelled a decade ago, has begun operating without a hitch.
Most sobering, perhaps, is that the crowded maiden image of deep space shows a vanishingly small piece of the night sky, equivalent to the size of a grain of sand held at arm’s length. Each dot or disc represents a galaxy that itself is made up of millions, even billions, of stars. Each grain of sky contains more worlds than it is humanly possible to contemplate.
It feels somehow fitting that this revelatory telescope is an international collaboration between Nasa, the European Space Agency and the Canadian Space Agency, comprising the efforts of an estimated 20,000 people across multiple institutions, companies and universities. It has taken the collective best of humanity to demonstrate our own colossal insignificance.