In my December 2021 column I said: “Hold your breath” over the forthcoming launch of a rocket carrying the James Webb Space Telescope, JWST.
Flawlessly it carried 18 separate large concave mirrors 1,500,000 km away to a special place in space, directly overhead if you are on the equator at midnight. There it will stay, the Earth blocking the sun, as will a heat shield allowing the telescope to be kept at minus 266 degrees Celsius (minus 450 Fahrenheit). Eighteen hexagonal mirror segments, folded like origami, opened and assembled themselves into one 6.5 m diameter concave mirror. Those mirrors had to be delicately positioned with minute adjustments so that together they made one perfect mirror, a process that took months. Only then did the team of astronomers show us amazing images of the very first stars and galaxies, using infra-red radiation that was emitted 13 billion years ago.
The JWST will be able to test theories about the very early universe. Some galaxies appear as distorted streaks, their images bent by the gravity of closer, but still very distant, clusters of galaxies.
The first stars condensed out of gas that originated in the Big Bang and should have only hydrogen, helium and a little lithium. They should not have any of the elements necessary for life, like carbon and oxygen, which were made when those first stars exploded, and the first planets were formed from the debris.
The JWST will also discover more exoplanets, planets orbiting distant stars, and in some cases even measure the composition of their surfaces and atmospheres. When planets cross in front of their parent star, starlight passing through their atmosphere is absorbed at specific wavelengths corresponding to the different gases present. Since life affects the composition of the atmosphere, this may lead to the discovery of “biosignatures,” signs of life on exoplanets. I mean primitive life as it existed on Earth for about 4 billion years before the industrial revolution started burning fossil fuels and emitting carbon dioxide. Water vapor in the atmosphere of a planet that is neither too cold nor too hot, a “Goldilocks planet,” would suggest that life is possible. Detecting oxygen in a planet’s atmosphere would be a sign that photosynthesis is occurring, as would a seasonal variation in carbon dioxide. In the next 20 years of JWST operation that may be the discovery of the century – but I cannot hold my breath that long!