Square Kilometer Array against the James Webb Space Telescope

The late-December headline-grabbing launch of the James Webb Space Telescope is humanity’s latest attempt to learn more about the origins of our universe. Like the Square Kilometer Array (SKA), the James Webb had been in the engineering pipeline for decades.

The SKA is a much larger project, coming online in stages with “precursor instruments”. The last of them, MeerKAT, has been in business since early 2018 and has been producing award-winning science ever since.

James Webb, meanwhile, made his first (and only) public appearance at the end of December before being propelled into space and forward until its possible orbital resting place.

So why do we still need the SKA? This article aims to clear the cosmic air and explain why newer isn’t necessarily better – just different.

One way to think about the difference between the James Webb and the SKA is to compare a new pair of reading glasses and the latest pair of headphones. Both reinforce a particular meaning to bring clarity.

Reading glasses improve your eyesight and don’t really affect your hearing (if you wear them correctly). A pair of headphones acts exclusively on your hearing.

The electromagnetic spectrum. Source: NASA Science

The SKA and the James Webb pick up waves on the electromagnetic spectrum. The spectrum extends from radio waves and microwaves to infrared, visible light, ultraviolet and X-rays, to gamma rays.

Both telescopes operate outside the visible light range of the spectrum, SKA in the radio range and James Webb in the infrared range.

The SKA “tunes” to the radio frequencies of cosmic objects that are emitted within its range of interest.

Just as your car tunes into a local radio station using the antenna on its roof, the telescope picks up radio waves from space through several receivers (or dishes) located in the Karoo.

The SKA’s bands of interest are much higher than the frequencies radios broadcast on, so it can’t listen to your morning news any more than your car radio can pick up the sound of an exploding star. .

The James Webb, on the other hand, looks at waves near the infrared part of the spectrum. So while both are designed to capture as much incoming energy as possible, they study entirely different types of waves: the James Webb in (near) infrared and the SKA in radio.

Of course, the two telescopes differ in a few other aspects.

Image of the galactic center of the Milky Way taken by MeerKAT, shown during its inauguration. Image: SARAO

The James Webb is deployed in space, and far beyond. The SKA is based on Earth, in our own backyard.

The James Webb is complete in construction, built as a single unit, and will never be as powerful as it is now – until a quantum leap in space travel facilitates ongoing repairs. The SKA is a much longer term project, stretching across Southern Africa and Australia.

In its current form, the precursor to the SKA, MeerKAT, could be the most powerful radio telescope ever built, and the SKA can only get more powerful as the number of receiving units reaches its full potential.

The goals of the James Webb and the SKA may overlap in some cases, but overall they are quite different.

The main scientific objective of James Webb, one of many, is to seek out the first light in our universe, where the first stars and galaxies formed.

Since it only takes so many hours of the day, the telescope will also examine exoplanets in nearby galaxies, with the aim of deciphering their chemical makeup – ultimately their similarity to Earth.

The SKA is significantly larger and more capable than similar instruments that have come before it, and the telescope’s size and reach allow it to meet a range of scientific purposes.

Investigations of our own Milky Way have provided groundbreaking results, and collaborations with the SETI group aim to achieve equally astonishing results far beyond that.

The SKA aims to provide many scientific abilities from imagery to pulsar synchronization. It is, by design, the most suitable for Hydrogen intensity mapping.

This maps the intensity of hydrogen gas in space. Since hydrogen has been shown to be a cornerstone of cosmic evolution, this ability is invaluable to those exploring beyond our solar system.

NASA’s Spitzer Telescope’s Helix Nebula which captures images in the same frequency band as James Webb. The images shared here are representative of cosmic observations in the respective frequency bands. It should be noted that while these are in color, observatories simply use a color palette to represent the energy intensity at different points. The higher the value, the brighter it is visually. In addition, the nature of the elements that these telescopes study varies. Source: Nasa

Then, of course, there are the particular benefits that SKA brings to South Africa. The scientific discoveries already made by the precursor instrument MeerKAT have brought interested parties from all over our shores.

Absolutely 16 partner countries are involved in the SKA.

South Africa and Australia were chosen as hosts for the physical instrument, and there was significant membership from institutions around the world.

Partner institutions provided hours of development engineering, and unofficial collaborators recognized the value of collaboration in this radio astronomy space.

Moreover, the vast majority of engineering work and scientific discoveries have been made by people here in South Africa.

The mere existence of this instrument has inspired a generation and a half of new engineers and scientists (including me) to pursue scientific careers.

Differences between the two telescopes

S.K.A. James Webb
Largest array of telescopes ever built, located in South Africa and Australia but hampered by Earth’s atmosphere and light pollution A single telescope 6.5 m in diameter located 1.5 million km from Earth in tip L2, with a much clearer view of celestial objects than the SKA
Will be used for decades Expected life of five to ten years
Useful for studying objects billions of light-years away (the early universe) to nearby stars The main purpose is to study the very first universe
Ability to support the work of many astronomy research groups around the world Able to support the work of far fewer astronomy research groups than SKA
Easily maintained and expandable Unless there is a major development in space travel, its current capacity is its maximum capacity
Operates in the frequency range of 580 MHz to 12 GHz (MeerKAT currently operates at ~1.7 GHz) Operates in the frequency range of ~10-500 THz (0.6 to 28.5 micrometers)

  • Video explaining SKA
  • Video explaining James Webb

By Amish Patel, digital signal processing engineer at the South African Radio Astronomy Observatory (SARAO).

This article was originally published on GroundUp. It is republished as CC BY-ND 4.0.

Read now: Funding the construction of a massive R8.8 billion telescope – how South Africa will benefit

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