The James Webb Space Telescope

Since the human race emerged on Earth several hundreds of thousands of years ago, men have been looking up at the sky in wonder, asking some very big questions. Why are we here? What are stars? What is the Universe made of? Are we alone out there?

In the past centuries we made sensational discoveries, pushing the boundaries of our knowledge to unimaginable levels and thanks to some brilliant, visionary minds today we’ve got a fundamental understanding of the Universe. For instance, we know what stars are, how they form, evolve and die; we built tools that helped us mapping the Universe, with its billions of galaxies, quasars, black holes and so on. We sent probes and humans into space…even a dog once, poor little thing!

So do we have all the answers now? No, we most certainly do not but we are still driven by our curious nature and thanks to a joint effort among NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA), we are now ready to send into space the most advanced telescope ever built, which will help unravel some of the unresolved mysteries of the cosmos.

This is the James Webb Space Telescope (JWST), a 6.5-tonne telescope with a cost tag of nearly 10 billion dollars (8.9 billion euro), which is set to be launched aboard the European Ariane 5 rocket on December 25, 2021 and begin its science observations 6 months after.

Having a telescope in space helps with the two main problems that ground-based astronomers have to face: the weather (clouds are astronomers’ worse nightmare) and the Earth’s atmosphere, which acts like a protective blanket letting only some light through while blocking or distorting some wavelengths. Besides, a space telescope doesn’t have to wait for the Earth to spin to be able to point toward the desired target.

Currently there are several telescopes in space, the most famous being Hubble, which has been orbiting Earth since more than 30 years, delivering iconic images and contributing to more than 15 000 scientific papers. As the JWST is widely considered the successor of Hubble, regardless of some major differences, it is understandable why the excitement around the new observatory grows by the hour within the scientific community.

Credit: NASA ®

The JWST is a powerful observatory, brimming with innovation and complexity. It boasts an impressive primary mirror with a diameter of 6.5 meters, composed of 18 adjustable, gold-plated beryllium segments, which has six times the light-collecting capability of Hubble, and a roughly 15 times wider field of view. It will be equipped with four main scientific instruments, collectively known as the Integrated Science Instrument Module (ISIM):

  • A near-infrared spectrograph (NIRSpec) that can observe 100 objects simultaneously
  • A near-infrared camera (NIRCam)
  • A combined mid-infrared camera and spectrograph (MIRI) with a cryocooler to keep its temperature at –266˚C
  • A fine guidance system and wide-field imager (FGS/NIRISS) that includes a mode for exoplanet spectroscopy

The JWST’s main goal is to look back to 100–250 million years after the Big Bang, when the first stars and galaxies formed, to shed some light on the so-called “end of the dark ages”. According to the Big Bang theory, this is when the Universe began to fill with “first light” from newly ignited stars. By comparison, Hubble was “only” capable of looking back 500 million years after the Big Bang.

Moreover, the mid- and near-infrared cameras will allow the new observatory to peer into the birth of new stars and solar systems and will be sensitive enough to detect oxygen and other so-called biomarkers in the atmosphere of exoplanets (planets orbiting stars outside the Solar System). The JWST will also study the effects of black holes and the origins of life; it will provide a better calculation of the Universe’s size and geometry, getting some insights on dark matter and dark energy, and helping us understand the ultimate fate of the cosmos.

The capabilities of the James Webb Space Telescope are huge but so are its risks. The JWST, in fact, will be folded down to fit inside the Ariane 5 rocket and, once deployed, it will unfold itself, cool down and calibrate in a process that will likely make all those involved in the project lose their sleep.

The JWST folded into the Arian 5 rocket – Credit NASA ®

On top of that, the JWST will position itself beyond the reach of manned repair missions as it will be orbiting the Sun at the Lagrange point 2 (L2), approximately 1.5 million km from us where it will have unobstructed views of the Universe.

Keeping the JWST in orbit around L2, however, requires an astonishing amount of energy and the on-board fuel will guarantee a limited lifetime (5 to 10 years), which should still be enough for some sensational discoveries. So brace yourself and be ready for the main scientific event of the 21st century!