SAVVA POUROULLIS
If you look at the progression of our knowledge of space over the last 20 years, the figures are astounding. When the Hubble Space Telescope was launched in 1990, it heralded a new age in astronomy. Hubble shook up the scientific community with the instruments necessary to peer deeper into the cosmos than ever before. With constant upgrades and repairs, Hubble became the prime hunter of newfound knowledge about the history of the universe.
25 years down the line, Hubble’s replacement, the James Webb Space Telescope, is well under construction in order to bring humanity closer to unlocking more of the secrets of the universe. Named after the man who helped turn Nasa into an organisation focused primarily on science and research, the fittingly named telescope will not be orbiting the earth, as Hubble does. Instead, Webb will be orbiting the sun at the same rate as the Earth, hiding inside our planet’s shadow to protect itself from the sun’s powerful rays while it absorbs light from the furthest reaches of the observable universe – the faintest light ever captured by a telescope.
This $8.7 billion project is shaped somewhat like a star destroyer from Star Wars, but is roughly the size of a tennis court. While it is difficult to comprehend the size of its 6.5 metre mirror, the instrument with which the telescope captures light, its scale has been made comprehendible by a life-sized model on display in the streets of Austin, Texas. Webb boasts a primary mirror with an area 6 times larger than that of Hubble, yet it has half the mass due to recent technological improvements in the space industry.
According to Nasa, the position of Webb over 1.5 million kilometres away from Earth will allow its infrared instruments to see far more clearly than any of its predecessors or any land-based instruments, despite being much smaller than many telescopes on the ground. Everything with heat gives off infrared radiation, turning the earth and even the telescope itself into a source of interference by swamping its sensitive instruments with infrared radiation. As a result, Webb’s four main observation instruments will have to operate at temperatures lower than -223°C to limit how much it radiates. One instrument will have an additional cooling system to create an operating temperature of -266°C. Despite being positioned so far from Earth, this is still not enough to maintain this temperature so it will have a sunshade behind it to block light and infrared radiation coming from the sun, the earth and the moon.
Webb will be the first telescope to achieve such sophisticated observations at infrared wavelengths. As a result, we can expect unique and revolutionary observations from its ability to see light closer to the beginning of the universe than ever before. Light takes a certain amount of time to travel from one place to another. This means that over large distances, the light you see represents what happened at that place a long time ago. However, it gets harder to see light as it travels further because it is very faint. According to Nasa, “Hubble can see the equivalent of ‘toddler’ galaxies and Webb will be able to see ‘baby’ galaxies.” While that may sound like a small increment considering the telescope’s $8 billion budget, this means we will be able to see about 280 million years closer to the creation of the universe. Before Hubble was launched, the scientific community was fairly confident that the universe was somewhere between 10 and 20 billion years old. Thanks to work done with the Hubble telescope, we now know its age to be 13.8 billion years and, as a result, we have totally remodelled our perception of our universe. It takes the wildest imagination to envision what might be achieved with Webb.
Nasa is working with 16 other countries on the project, including collaborations with the Canadian Space Agency and the European Space Agency, both of which are contributing instruments and expertise in exchange for a fraction of Webb’s usage time. The telescope is expected to have a service life of over five years, but carries enough fuel for ten. If Nasa wanted to continue its use of the costly telescope, it would have to be towed back into Earth’s orbit. Thus, managing to book a slot with the unique telescope during its workable time would be a feat in itself.
One major advantage Hubble has over Webb is its close proximity to Earth, meaning that it can be regularly repaired and upgraded. While no more trips to Hubble are planned, the telescope should continue with its impressive lifetime for another five years. Hubble is also far more powerful than it was when it was first launched, thanks to a multitude of upgrades and tweaks to its systems, and would not have worked properly at all before its first service due to a flaw discovered right after its launch. Today, Hubble is at its operating peak.
Nasa has taken unexpected problems into consideration, of course, and over-designed Webb to remain in near-perfect operating condition even if a whole slew of problems, such as a faulty gyroscope, arise. Hopefully the scientific community can look forward to a decade of fruitful discoveries
