"Light brings us news of the universe."
-William Bragg
The study of light is one of the most exciting fields of science. Light is something whose behavior, even after decades of research, we've only just begun to understand. Our perception of its nature has changed from believing it consisted of particles to waves to both in a matter of years. But the one thing that has remained constant is its speed.
The speed of light is a universal constant. No object with a finite mass can achieve the speed of light. It is so fast, in fact, that our human brains aren't even capable of seeing it in action. To us, every action we observe happens instantaneously without delay. But just as observing the splitting of a cell requires a microscope, we only come to realize the limitations of light when we look at it through a telescope.
Even light can not cover interstellar distances in an instance. The light from the Sun takes about 8 minutes to reach the Earth. So hypothetically, if the sun were to switch off suddenly, we'd only realize it 8 minutes later. The Sun we look at during the day is actually the sun from 8 minutes ago!
And this delay in light reaching the Earth increases as we look farther in space. The deeper we peer into the depths of space, the further into the past we glimpse because light takes longer to reach us from far away.
This phenomenon has some interesting consequences.
The universe is estimated to be 13.7 billion years old. If we were to build a telescope that could collect light from up to 13.7 billion light-years away, we could potentially observe the inception of the universe!
Building towards this exact goal is the next step in space telescopes, which is the James Webb Space Telescope or JWST.
The Hubble Telescope
Before talking about JWST, let's first talk about the boss of all telescopes, the Hubble telescope. An instrument that revolutionized astronomy as we know it, led to many scientific discoveries and aided numerous scientific papers. The Hubble telescope, orbiting far above the distortions created by the Earth's atmosphere, captures the most stunning pictures of the galaxy and beyond in infrared, visible, and ultraviolet spectra.
It is a type of reflector telescope whose broad mirrors collect electromagnetic waves from all around space and the sophisticated instruments inside the telescope analyze those waves to give us mesmerizing pictures of nebulae, galaxies, stars, and so forth.
Credits:NASA
It was launched by NASA in 1990 and continues to serve its purpose to this day, after 30 years. After such a long period of service, the time has come for a successor. While the Hubble telescope has captured images from as far as an impressive 13.2 billion light-years, its successor aims to capture images from a whopping 100 million years after the big bang.
Credits: NASA and Ann Feild
That successor, of course, is the James Webb Space Telescope.
The James Webb Space Telescope
The James Webb Space Telescope, named after NASA administrator James Webb who worked from 1961 to 1968, has been in development by NASA since 1996. It is the next step in space telescopes, set to be launched in 2021. It is not to be a replacement to the Hubble telescope but instead a successor. While the Hubble telescope gathers data from infrared, visible, and ultraviolet regions of the spectrum, James Webb will primarily collect data from infrared wavelengths. The reason behind this is something called the doppler effect.
The universe is expanding, which means the farther an object is from us in space, the faster it is moving away. This causes light from such objects to redshift. In simple terms, light emitted by these objects in the ultraviolet or visible regions gets stretched into redder wavelengths. Thus, to study the early formation of stars and galaxies, we need instruments that can study these red wavelengths.
Another reason to focus on infrared wavelengths is that star and planet formation takes place at the center of dust clouds. Visible and ultraviolet light cannot penetrate these dust clouds but infrared radiation, with its longer wavelengths, can easily pass through the dust particles.
Credits: NASA/JPL-Caltech/University of Colorado
So, while Hubble will continue its operations as it is, the JWST, with its greater sensitivity and higher resolution, will work to add to the discoveries made by the Hubble telescope and make its own contributions to the study of the cosmos. JWST aims to fill the gaps in knowledge we have in terms of the formation of galaxies, the placement of black holes at the center of galaxies, the possibility of life on other planets, and much more.
Credits: NASA
We wholeheartedly look forward to the launch of the JWST and the exciting discoveries just waiting to happen. Work on JWST has currently been halted due to the ongoing pandemic, but we hope to see a successful launch sometime next year.
Until then, we can always still look towards the Hubble telescope for some terrific pictures of the cosmos or our own backyard telescope to study the craters of the moon again. But even if you don't own a telescope, we still have our eyes to admire the beauty of nature. They may not have as high a resolution, and they may not be able to peer deep into space, but they have been just as instrumental in making some great discoveries right here, on our very own planet.