If all goes well, this December 22, the James Webb Space Telescope (JWST) will be launched on top of a French Ariane 5 rocket from French Guiana. Originally called the Next Generation Space Telescope, it was renamed by NASA in 2002 to Director of NASA from 1961 to 1968. JWST is a joint effort of NASA, the European Space Agency and the Canadian Space Agency , and the chief construction officer is the Goddard Space Flight Center in Green Belt, Maryland. But before I describe the JWST and its mission, here’s a bit of background.
Light is an incredible gift of creation. In the light rays are spectral lines that reveal which chemical elements emitted this light and which gaseous elements the light has passed through. In 1868, rays in the sunlight revealed a new element, helium, discovered only later on Earth. The frequency of spectral lines in the elements also tells us how fast the object is moving away or approaching us. The frequency shift of the spectral lines of distant galaxies reveals that distant galaxies, in all directions, are flying away from us at fantastic speed. Imagine dots painted on a balloon. As the balloon expands, the points move away from each other. No matter which point you choose, its neighbors move away. The universe is expanding. The light reveals even more. As Einstein predicted, light passing through massive objects is bent. The geometry of this effect provides an estimate of the mass of this object. In other words, the gift of light reveals the secrets of the universe.
Galileo was the first to turn a telescope to the sky. The quest for a better understanding of the universe has led to the construction of ever larger telescopes. However, the atmosphere distorts the light passing through it. The Hubble Space Telescope solved this problem by observing the sky above our atmosphere. Hubble was small compared to many terrestrial telescopes, but its undistorted view led to many important discoveries. Hubble peered deep into space, but that deep sight led to a new problem.
Expansion means more distant galaxies are moving away from us faster. Visible light is only a particular frequency range of the electromagnetic spectrum. The higher frequency waves are x-rays and gamma rays, the lower is ultraviolet, the lower frequency is the visible spectrum, then infrared and heat. The lowest frequencies are radio waves. As light reaches us from more and more distant galaxies, its frequency is shifted more and more downwards. Light from the most distant galaxies is shifted below the visible domain towards the infrared, which is heat.
Hubble would have been able to see to the edge of the universe, except that light from the edge of the universe is shifted towards heat and Hubble’s sensors are heat blind.
So, in 1996, planning began for the JWST to replace Hubble. The goals were sensitivity to infrared waves and a larger mirror to see more detail. To improve infrared sensitivity, the telescope will be kept very cold at -370 degrees Fahrenheit. JWST must be protected from the Sun, and even from the heat of the Earth and the Moon. A large shield with five layers of reflective film as thin as human hair will protect the JWST mirror and instruments from the rays of the Sun, Earth and Moon. To keep these bodies on the correct side of the shield, JWST will park in a special orbit 930,000 miles from Earth, more than three times the Moon’s distance from Earth. Because the mirror has a larger diameter than any launch rocket available, once in space, the mirrors and shield must deploy with unimaginable precision.
The complexity has resulted in significant time and cost overruns. NASA initially estimated the cost at $ 500 million with a launch in 2007. During development, the schedule continued to slide and costs continued to rise. Because JWST was consuming considerable funds that might have been available for other programs, Nature magazine called JWST “the telescope that ate astronomy.” In 2011, Congress nearly canceled the program. However, construction and testing are now finally complete. As of this writing, the final construction cost of JWST is nearly $ 10 billion, with a launch slated for December 22.
The risks are high. JWST is a very complex machine. Unlike Hubble, its orbit is too far away for any service mission. Astronauts have serviced Hubble five times. JWST is a giant bet. However, the potential rewards are – well, shall we say – astronomical. The light is fast, very fast. But since light travels from deep space, it takes time. JWST is a kind of magical time machine. The light that reaches us from the edge of the universe began its journey at the beginning of time, creation. Only time will tell if JWST ate astronomy or had a feast. The award answers the most pressing questions in astronomy. Watch the launch! The mission is for all balls.
Would you like to learn more about telescopes and deep space, or do you need a gift for the curious? My book Astronomy is Heavenly is available at the Thomasville Library and on Amazon.