Quite the view

NASA’s new James Webb telescope will let us observe the past, present and future
By Robert Mead | Current affairs | 14 September 2020

Image courtesy of NASA.

The James Webb Space Telescope will be the largest ever built by NASA and successor to the current Hubble telescope. It will look further into space than ever before, allowing us to gaze through the history of the universe. Once completed and launched into orbit, astronomers will use it to study how planets and solar systems are born, bringing us closer to revealing the origins of the universe and humanity.

In his role as Senior Project Scientist, Nobel Laureate and scientist Dr John Mather is a leading figure behind the project. Having won the 2006 Nobel Prize for Physics (shared with George F. Smoot of the University of California) for his work using the COBE satellite to measure heat radiation from the Big Bang, this latest venture sees Mather zoom in on the universe’s most intriguing mysteries.

Robert Mead: The James Webb telescope will allow us to look further into space than ever before. What are key differences between the James Webb and the Hubble telescope that allow this?
Dr John Mather: The obvious one is it is a lot bigger, which allows it to see fainter things that are further away. The less obvious one is that it is cold, so it can observe infrared light. The expansion of the universe stretches out light that we receive from the most distant objects so that it is infrared instead of visible or ultraviolet. The wavelength is longer, so we need an infrared telescope to see what started out as visible or UV. This allows us to see further back in time.

RM: What will the James Webb be able to show us that the Hubble cannot?
JM: We’re looking for everything, from the first objects after the Big Bang until now. So we will be looking further back in time to see what grew first, whether they were stars, galaxies or black holes. It’s hard to tell at the moment, so we want to just look. We know more or less how we would recognise them if they are there, so that is one of the hardest problems for us to work on, but also one of the most important.

RM: What can we learn from seeing this far into space?
JM: Part of it is the general subject of how did we get here? What’s the history of humanity? We can start putting together all the pieces: we know there was the Big Bang, we know something happened to produce stars and galaxies, and we know it is pretty likely that galaxies grow from collisions of little bits. When we look back in time, we can see if galaxies were really very different and, so far, the evidence is that yes, they were, which is very interesting. Another thing is that our Milky Way has a black hole in the middle and so do most galaxies. Does that happen because the galaxy produces a black hole or does the black hole come first and produce the galaxy? That’s a very interesting question.

RM: Will we be able to learn about the lifecycle of stars and galaxies and the order in which things occurred?
JM: That’s certainly the hope and we will definitely be looking for this. Closer to home we are going to be looking at stars being born today. Infrared light goes through dust clouds better than visible light, so that means we can see inside those dusty clouds – like the Orion Nebular, the Pillars of Creation and all those beautiful pictures you see – and examine what is really happening inside, so that’s pretty cool. It has been very frustrating because since I was a kid we have been learning that stars were being born but we still can’t see it happen.

RM: But with the James Webb you think there is a good probability of seeing this?
JM: Yes, and closer to home we will be looking at things in our solar system – nearby planets and other stars that Hubble can’t clearly see because of the infrared. Robert: Could you give an explanation of how the telescope allows us to see back through time? John: Because light travels at a speed, if you look at something that is far away then you know that the light has been travelling for an amount of time. We know the speed of light so then you have to measure, if you can, how far away something is and then you know how far back you are looking in time. It’s really simple but hard for people to appreciate sometimes.

RM: In terms of seeing our past, what do you think it means for humans to understand the history of the universe? Do you think it raises questions of what is to be alive and why we are here?
JM: For some people, it is a deeply emotional thing to know that story. It’s certainly something humans have been thinking and writing about for thousands of years. So to think that we can maybe gather some evidence that can tell you what really did happen, and that it’s not just a story about the turtles and so forth, is very exciting for me and many people. I used to sit on the subway train in New York City, carrying my astronomy books and everybody would ask me what we are doing, because the general public cares a lot about what we do.

RM: How do you think the new information received will contribute to previous theories, such as the theory of relativity?
JM: It would be surprising if anybody could find any mistake in Einstein’s work because we’ve had centuries to do so and nobody has. The theory of general relativity has passed every test, you never know what you are going to see, but that would be very unlikely.

RM: With subjects of the universe that are less known, such as questions around dark matter, can the telescope offer more answers?
JM: Yes it could, and that one is a really open question, because dark matter is mysterious. We know it is really important, if you look at the microwave background maps and the hot and cold spots in the Big Bang, most of them come from dark matter. We are here because of dark matter, it made the first objects and then galaxies grew around that, that’s the way it looks to us. It’s everywhere. Of course, by definition, you can’t see it, but you can observe its effects. We should see an effect of the dark matter on the formation of all galaxies, from our own galaxy, all the way to the most distance ones. So we will certainly be working on that question.

RM: Will the telescope also be able to examine atmospheres and identify habitable planets?
JM: We will certainly look, although calculations say that we probably cannot find them ourselves because the telescope was not originally designed for that. We will look for signs of water, we might be able to see this on planets the size of Earth, which would be very exciting. We’ll look for signs of oxygen, however we don’t think we will be able to see this.

RM: Will infrared play a part in studying these atmospheres?
JM: There are different molecules and wavelengths, a lot of molecules have much stronger absorption features and infrared wavelengths than they do short visible wavelengths. That’s why we have a climate issue here on Earth, the carbon dioxide holds in the infrared and so does the water. So, water and carbon dioxide and all the other molecules have vibrations inside them that can absorb this light and those wavelengths. There is a reason infrared is superior for looking for these molecules, but it doesn’t mean we will be able to do it successfully.

RM: How will the telescope be launched?
JM: On a European rocket, The Ariane 5, because the Webb telescope is an international partnership project. Europe, Canada and the US are all contributing to it. Europe actually built one instrument and part of another one and they are buying the rocket. We are going down to Kourou for the launch, a little island off the coast of French Guiana in South America.

RM: Is there a particular place in orbit that the telescope will be positioned?
JM: We’re sending it to a place called Lagrange Point 2, which was discovered in 1750 by a man called Euler. This is a place where the combined gravity of the sun and the Earth will tug the telescope around the sun once a year. It is a curious spot, simultaneously orbiting the sun and Earth. Robert: Whereabouts in relation to the Hubble will it be? John: It will be much further away. The Hubble is in orbit just a few hundred miles above the surface of the Earth, the Webb telescope will be, to use metric units, 1.5 million km away. Robert: This project has been ongoing for a long time, have you personally been working on it from the start? John: Yes I have, since October 1995. It’s a hard project and it’s a long project but it is definitely the most exciting thing I can imagine working on.

RM: What is your personal ambition for the telescope?
JM: My ambition is that it works beautifully for all who choose to use it. I am actually not a user of telescopes, more a builder of them, but we expect every astronomer in the world is going to be using the data. In a couple of weeks we will have a call for proposals. Every astronomer can write a proposal, to say, “I have an idea, please think about it.” If we agree, we will take the picture you ask for, and give it to you. Eventually all the data will become public, so everyone around the world will be able to see it for free.

RM: So the general public will be able to see the imagery that is coming from the telescope? Will this be part of a wider programme to both educate and exchange knowledge?
JM: Yes. For me the information we get here is only part of the story because it is part of the great scientific enterprise, where we are trying to learn how to do everything and understand everything. In particular, this is our little bit of the story of humanity. As you know, our pictures of space are beautiful and they are one of the ways that we attract young people to be scientists, but then they will go on and become geologists, biologist, chemists, mathematics and everything else we need in order to propel science forward.

Top image: Support structures wrapped in gold thermal blankets that resemble a golden cage. The structure is housed within the vacuum chamber called the
Space Environment Simulator, or SES. The SES is located at NASA’s Goddard Space Flight Center in Greenbelt, Md., where components of the James Webb

Space Telescope are tested to withstand the extreme temperatures of space. Image courtesy of NASA.

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