Since its launch in 1990, the world-famous Hubble Space Telescope has revolutionized our comprehension of the universe with its more than 1.4 million observations and 18,000 published articles. And now, with the successful 2021 launch and March 2022 deployment of the James Webb Space Telescope (JWST), the revolution that Hubble unleashed will accelerate.
The JWST delivers a significant increase in observation data (NASA image)
The Hubble helped pin down the age of the universe, determine the rate at which the universe is expanding, and observe that nearly every major galaxy is anchored by a black hole at its core. Besides contributing to scientific advancements, Hubble is also responsible for the popularization of astronomy. Many of the most famous images of space, those that have caught the public’s eye and imagination, are mostly from Hubble’s observations. In the last three decades, Hubble changed the way we approach astronomy. Yet, Hubble’s characteristics limit how deeply scientists can dive into the secrets of our universe.
Hubble’s image of Star-forming region S106 (NASA image)
Designed to be the successor to the Hubble Telescope, the James Webb Space Telescope (JWST) is a much more complex instrument with even more ambitious goals. First conceived in 1996, the JWST required the creation of new technologies and processes and cost nearly $10 billion to develop.
The JWST does not study the visible and ultraviolet parts of the electromagnetic spectrum of the universe’s energy, as the Hubble does. Instead, it gathers only infrared radiation. According to Dr. Gillian Wright, director of the UK Astronomy Technology Centre in Edinburgh, there are many reasons to focus on infrared: “For a start, infrared is the perfect part of the spectrum for looking through dust, and that is important because stars and planets form in regions full of dust”. In addition, infrared solves another problem: the universe is in constant expansion, and that means that the space and time are being stretched so that the more distant an object is, the faster it moves away from us. Due to a phenomenon called redshift, this expansion means that we are constantly receiving infrared light with information from extremely distant parts of the universe. But this information was being lost because we did not have a telescope capable of catching it, until the JWST began operation this year.
Redshift: “The term can be understood literally – the wavelength of the light is stretched, so the light is seen as ‘shifted’ towards the red part of the spectrum. Something similar happens to sound waves when a source of sound moves relative to an observer”. [The European Space Agency.]
Webb’s images will appear just as sharp as Hubble’s, but with greater detail since it is optimized to see deeper into the infrared than Hubble and has a much larger mirror, as well as state-of-the-art detectors. The JWST collects light in an area 6.25 times larger than the Hubble’s, using 18 hexagonally shaped mirrors. These rearrange automatically to combine in a 6.5-meter (21 feet) surface.
The mirrors also received a thin layer of gold, a better material to reflect the infrared. The telescope’s sensitivity to infrared is so extreme that it must be maintained at extremely low temperature, near the absolute zero (around 7 Kelvin, or -266.15º Celsius), so it doesn’t capture infrared radiation generated by the heat of its own operation. Furthermore, the telescope is protected by a shield that is five layers thick and will block radiation from the sun and Earth. The light-collecting surface in JWST is about seven times larger than Hubble’s. A telescope this large has never been launched into space.
The JWST will allow a giant leap in almost all areas of astronomy.
It was created to capture the light that arrives at every moment on Earth and make it possible for us to understand what happened as far as around 13.5 billion light-years from Earth. In other words, we will be observing objects and regions of the universe exactly as they were up to 13.5 billion years ago. As our universe itself is believed to be about 13.8 billion years old, this means we will be able to observe the universe when it was extremely young, when it was only a few hundred million years old. Already, the JWST has produced an image of Earendel, the earliest and most distant star in the known universe that was first detected by Hubble.
The JWST will bring us closer to understanding the origins of galaxies and supermassive black holes, the formation of the first stars, the atmospheres of planets outside our solar system, and many other aspects of the physics of the universe. It could shed light on the eternal questions: where did we come from, and why did we become? Astronomers hope to understand how stars are born and evolve, and investigate the potential for life in planetary systems. The JWST will be able to detect the presence of planetary systems around nearby stars and to observe directly the reflected light of large planets orbiting around nearby stars, as well as very young planets in formation, while they are still hot. Additionally, while astronomers cannot directly detect dark matter, which is thought to constitute about 27% of the universe, the JWST will be able to measure its effects with greater precision.
James Webb Space Telescope folded for rocket launch
Unlike the Hubble, which orbits Earth at a distance of 570 km, the JWST sits at 1.5 million km away from the planet. Far beyond the orbit of the moon, in a region called L2 where the gravity of Earth and the gravity of the sun cancel each other, it is possible for the telescope to remain stationary in roughly the same position requiring minimal energy. Delivered to L2 by the Ariane 5 rocket launched from French Guiana, it can operate continuously with only a few corrections required.
After it reached L2, JWST deployed key components that were folded up to fit inside its rocket. This process involved approximately 180 release mechanisms, each of which operated flawlessly for the telescope to self-assemble and complete its many major deployments. The first images from the JWST were released by NASA on July 12.
Select astronomers have been training with the telescope on a wide range of targets, from distant galaxies to planets in our solar system, to gain experience with the nuances of this new instrument and share that knowledge with the rest of the astronomical community.
The power of the James Webb Space Telescope marks the beginning of a new scientific era.
Who knows, perhaps the universe will finally unveil some of its long-held secrets. “It’s going to help us unlock some of the mysteries of our universe. I want to say it’s going to rewrite the physics books” says Dr. Greg Robinson, Webb’s program director at NASA.
