The Week in Space and Physics #22
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The Week in Space and Physics #22
On the James Webb Space Telescope
As the James Webb Space Telescope soared skyward last Christmas morning, success looked far from certain. Controllers had weeks of operations ahead of them, a voyage of more than a million miles and the delicate unfolding of the largest mirror ever put in space. Failure could happen at any one of over three hundred steps. So far from Earth, any flaw in the design would have been fatal.
And yet, after half a year of effort, the James Webb has proven a tremendous success. The first images, unveiled last week by President Biden and NASA, are remarkable in their clarity; offering the sharpest and deepest view of the cosmos yet seen. Even better, the telescope is likely to keep working for a decade longer than planned. Thanks to a pitch perfect launch, the James Webb has enough fuel to keep running well into the 2040s.
That will give astronomers plenty of time to probe the mysteries of the universe. The telescope will soon be directed to peer across billions of light years; to search for light coming from ancient galaxies. It will scan the atmospheres of exoplanets, hunt for moons around distant planets and survey the frozen outer worlds of our own solar system.
And yet, despite this promised bonanza of discovery, it is possible – and even worth – asking if it justifies the ten billion dollar price tag it comes with. In an era of rising costs, food and energy shortages and looming recession, the funds spent on science will surely be questioned. And, unlike many other fields of inquiry, astronomy offers little in the way of tangible benefits.
There will, of course, be some technological innovations coming from the telescope. It was one of the most complicated pieces of engineering ever attempted. The effort has inspired breakthroughs in optics, integrated circuits and laser technology. Those discoveries, and others, will surely lead to new technologies on Earth.
Yet the real benefit of the telescope is felt more subtly. Astronomy is not something we do for commercial gain, or to make ourselves materially richer. It has a deeper meaning: one intimately connected to the way we view ourselves as a civilization. It, like art or religion, is something we do to feel connected to the rest of the universe; to help us understand our place within it.
Just as centuries ago people poured vast resources into building pyramids and cathedrals, today we build observatories and put telescopes a million miles from Earth. The value of that is not measurable in the cold weight of dollars and gold; any more than the wonder and awe inspired by the telescope’s first images can be.
A Magnificent Showpiece
Over the winter holiday of 1995, controllers directed the Hubble Space Telescope towards an apparently empty area of sky. For ten days the telescope watched, carefully recording the photons it saw. The result was astonishing: the spot, a tiny fragment of sky, was full of galaxies: more than three thousand were later counted in the image, most of them extraordinarily old.
The image became known as the Hubble Deep Field, the deepest view of the universe humanity had ever created. It showed objects up to twelve billion light years away; almost to the edge of the visible universe itself. In the years since it has been celebrated as one of the most significant pictures ever created by Hubble.
It was fitting, then, that the first image released from the James Webb Space Telescope was a similar deep field. Controllers pointed the telescope, for a mere twelve hours, towards a distant galaxy cluster. Thanks to its huge mass, the cluster warps the surrounding space, magnifying and stretching whatever happens to lie behind it. The new image thus spans vast distances, showing galaxies over thirteen billion light years away.
Impressively, scientists were able to study one in detail: revealing the atoms present in a galaxy of enormous distance and age. Then, as if to prove the versatility of the telescope, they switched focus. Its power was concentrated on an exoplanet sitting a thousand light years away: WASP-96b. Again it revealed astonishing details: unexpected signs of water and clouds drifting through the planet’s atmosphere.
Three other images showed a set of cosmic objects in unprecedented clarity. Operators snapped the Carina Nebula, capturing glittering new born stars amongst clouds of gas. They observed Stephan’s Quintet, a set of five galaxies merging irresistibly into one. And they saw the Southern Ring Nebula: a star fading slowly, but beautifully, into death.
Amid the countless stars, planets and galaxies in these images, it is easy to feel somewhat lost. The Earth is an insignificant speck; one easily ignored in the vastness of creation. Yet the images also reveal the Earth to be something special. Amongst all those galaxies, stars and planets, nothing has yet been seen like our world. Ours is the only living planet known. The only place where life, civilization and technology flourish. That, surely, makes it all the more unique, and all the more important to protect.
A Perfect Deployment – But One Worry Lingers
The James Webb, scientists write in the final commissioning report, is performing far better than expected. In almost every area the telescope beat expectations. Its mirrors are cleaner, its optics better aligned, its instruments more sensitive than planned. The result is an observatory that will peer deeper than thought and work for twice as long as designed.
Only one slight hitch has been identified: the presence of unexpectedly big micrometeorites. Astronomers had known the telescope would get struck by the odd high speed grain of dust and rock, and designed it accordingly. Yet in late May the telescope was hit by a rock bigger than models had predicted and, thus, bigger than designed for.
The result was a slight disturbance to the telescope and a slight worsening of its ability to see. The effect is small – but astronomers are worried it will be an omen of things to come. The rock could have been a rare outlier; an unlucky early strike from an abnormally big grain. That would be good news: it would mean the telescope can survive for decades with little loss of performance.
But it could also be a sign that bigger micrometeorites exist than thought. If so, they would likely become a serious problem for the telescope: damaging its mirrors and degrading its view. In the worst case they may one day render the telescope useless, years earlier than its fuel reserves would allow.
The Science Begins
Beautiful as the first images from the James Webb are, they don’t yet represent a real start to scientific work. They are intended to show off the power of the telescope, to mark the end of commissioning, and to pave the way for the hard scientific work to begin.
Astronomers have spent years preparing for this moment. Many submitted proposals to use the telescope; to swing its powerful eye towards their favourite target. Hundreds of these have been accepted: setting up a busy first year for the new telescope.
Among the first targets are the remains of a nearby supernova, SN1987a. As the closest recent supernova, astronomers are keen to image the debris around it. That, they hope, could reveal clues about the dying moments of a giant star.
A second highly sought target is the TRAPPIST-1 solar system, a set of seven planets around a small red dwarf star. Several of those planets should be at the right temperature to be habitable. The James Webb has already started observing the system, searching for signs of atmospheres, water and, perhaps, life.
The Week in Space and Physics #22
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