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Next space telescope comes into focus

Friday, November 25, 2016 2:02
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Thought Experiments

NASA administrator Charles Bolden (centre) and senior project scientist John Mather (right) answer questions about the James Webb Space Telescope (rear) at NASA's Goddard Space Flight Center in Greenbelt, Md. (Postmedia wire service)

Unless you have been living in a cave, you probably have seen pictures from space originating from the Hubble Space Telescope.

Launched in 1990 at a cost of $2.5 billion US, the Hubble has been orbiting about 550 kilometres above the Earth, taking spectacular pictures of the universe. A defective mirror that made the Hubble slightly out of focus threatened the mission, which was saved by a heroic spacewalk that fixed the vision of the myopic telescope.

It is from Hubble that most people have their picture of what the universe is like.

Hubble brought us images of distant nebulae and galaxies, and detailed views of our solar system. Using the space shuttle, Hubble was upgraded with newer computers and sensors, and kept in tip-top shape.

However, Hubble is showing its age. The instrument’s lifespan now is limited to the amount of fuel on board and the mechanical condition of its systems.

For some time, scientists have been planning for the “next generation” of space telescopes. They have just completed the assembly of the new James Webb Space Telescope, which is on track to be launched in October 2018. Named after the second administrator of NASA, the telescope promises to revolutionize astronomy in a way not seen since the launch of the Hubble.

The Webb differs from Hubble. First, the primary mirror, the device that collects the light, is bigger. Hubble sports a mirror that is 2.4 metres in diameter. The Webb has 18 mirror segments that together give a clear aperture of 25 square metres and a diameter of about 6.5 metres. As well, the Hubble is designed to capture visible light, whereas the Webb is optimized to collect infrared light.

Infrared light is what we can sense as heat and has interesting properties that make it useful for doing science. Infrared light can penetrate dust and gas in our Milky Way galaxy and across the universe to give us a look at structures whose view is blocked by this dust and gas. The JWST will give us a look back to almost the beginning of the universe, helping us understand the structure of the Milky Way.

This new window on the universe will help us understand what happened to the universe over the past 13.5 billion years of galactic evolution. It will give us unprecedented looks at the earliest formation of galaxies.

Another benefit will be understanding how stars are born and die. Stars are formed in giant dust and gas clouds where they form planetary systems. They live and then die, often in huge explosions that spread dust and gas throughout space. This spreads the material for the formation of new stars and newer planetary systems. For the first time, we will get a window into that process.

Now that we have found hundreds of planets surrounding other stars than our own, we can use the Webb to learn more about the formation, orbits and even the atmospheres of these planets. This will help us in finding planets that might contain life.

Closer to home, the telescope will be used to study our solar system. With its unprecedented resolution, the Webb will be able to measure trace elements in planetary atmospheres and give us a better picture of the seasonal variations of weather on planets, such as Mars. It also will be able to get much more detailed views of small asteroids and minor planets to give us a better understanding of how our solar system evolved.

Unlike Hubble, the JWST will not orbit the Earth, but will be one million miles away in a parking orbit between the Earth and sun. This means that it is too far away to be serviced from Earth.

So, the telescope must have a much greater ability to troubleshoot itself and a great deal of redundancy to compensate for hardware failure. Space is an unforgiving environment and it is very hard on anything that must function out there. Temperatures cold enough to freeze most gasses in the shade and scorching heat on the sunward facing side of the telescope play havoc with sensitive components. This telescope must be built tough.

The Webb promises to herald a new era of space-based astronomy. I cannot wait to see the first pictures from this new telescope.

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