NASAs James Webb Space Telescope. Credit: NASA Goddard Space Flight Center and Northrup Grumman
Are you curious to know how a telescope works? Join ESA astronomer Giovanna Giardino as she offers an insight into the inner functions of the worlds largest telescope in space, the remarkable James Webb Space Telescope.
Video Transcript:
In very simple words, a telescope is a bit of a pail of light, bucket of photons. The primary elements of a telescope are really the mirrors or the lens that you utilize to gather the light and focus it. The tube, that we see in lots of telescopes that we utilize on the Earth, has generally two functions.
Exactly, and thats the factor of the sunshield, to keep the telescope and the instruments, the clinical instruments always in the shade of the Sun and the Earth. Space is really cold, its minus 270 degrees (celsius), so by keeping the telescope constantly in the shade of the sun we can cool it down to extremely low temperatures.
Most of us can picture a telescope.
Usually a long tube mounted on a tripod. Telescopes come in all sizes and shapes, and theyre some of the most effective devices in the world, and in space.But how do they work?
Im Laylan from ESA Education and today were asking an ESA expert dealing with the James Webb Space Telescope.
Welcome to our little studio. Thank you quite.
Dr. Giovanna Giardino, thank you for being with us today.
Thank you, thank you for the opportunity. Im very delighted.
What do you do at ESA?
So Im an astronomer and I work for ESA on the Webb Space Telescope.
I believe a lot of people visualize a telescope like my childhood telescope, so its sort of this tube, and even the Hubble Space Telescope is what everyone images as a telescope, this type of giant tube in area.
How does a telescope work?
In really basic words, a telescope is a bit of a container of light, pail of photons. Using a lens or a mirror that is inside this tube, you gather the photons, the light, from an item and concentrate it. Focus it in a specific point so that you have much more signal, much more light, for that item than you would have with your naked eyes. And that way you can see far away things, weak, weak signals.
However then you have the James Webb Space Telescope that looks entirely different, and yet its still a telescope.
Why does it have such a special style?
The main aspects of a telescope are really the mirrors or the lens that you use to gather the light and focus it. Those are what you have to have. The tube, that we see in lots of telescopes that we utilize on the Earth, has generally two functions.
One is the holding of the lenses, the lenses that you need or the mirrors. So you need to have a structure that keeps them in the location and with the right distance from each other, thats extremely crucial for focusing.
Choosing television enables you to obstruct off additional light from the surroundings that you dont wish to enter the lenses and disrupt the clear vision that you have on the sky. It likewise keeps it clean. In the environment every day there is dust and things, so the tube keeps it tidy.
So the reality that James Webb Space Telescope doesnt have this huge tube.
Yeah.
How is its structure being held together? How is it staying tidy?
So the structure is held together. The main mirror is mounted on the spacecraft and after that there is, if you notice, a tripod going off from the main mirror to what we call the secondary mirror.
And the light sort of enters the main mirror, the big container that I call. Gets focused on the secondary mirror, and then focused once again into the main focus of the telescope where the instruments are, and we actually collect the light and take a look at it in a spectrograph or a camera.
The camera, its actually an electronic camera, so like the name says we record images. The telescope collects the light, focuses and this electronic camera gathers it and records, so we see images, we can see the stars, nebulas.
And the spectrograph. The light entering a spectrograph is distributed with a prism. Or we also utilize gratings, however the principle is the very same. The concept is to look and distribute the light at the components of the light. So when you have noticeable light and you shine into a prism you see the colors coming through. Thats the spectra of the light.
These are the parts of the white light. The red, blue, yellow, thats the elements. And the exact same we can do in the near infrared and in the infrared, and we look at the elements.
And why do we do that?
Great concern.
Since in such a way, the light that an object gives off, its a little bit of the signature of the things. It tells us a lot of what the object is made of, which aspects are present, what temperature, whats the pressure, whats the physical condition.
And after that what about the well known honeycomb mirrors? Why is it a honeycomb, whats the structure?
So as you understand, the Webb Space Telescope is one of the largest telescopes ever released.
It is 6.5 meters in size, the main mirror. Even the main mirror would not fit in any of the fairings of the existing launchers.
The size is about 3 meters so the style has to be such that it might be folded for the launch to be fit into the rocket.
And I expect the honeycomb structure is what really permits you to be able to meet that?
Right the honeycomb, so that you desire a constant surface, right?
You dont want spaces, so the hexagonal, as the bees have actually discovered, its an extremely efficient method to tile a surface area, and also give it a rounded shape. You might do that with squares but then you wind up with a square telescope. Which is not perfect to focus the light.
The honeycomb mirrors are not just in a honeycomb shape, however theyre also this gorgeous yellow, gold color. What material are they constructed out of?
Each of them is covered by a really thin layer of gold.
And why gold?
Why gold?
Because gold, its a perfect reflector in the infrared. For normal visible light we frequently use silver or aluminum?
It shows extremely well in your mirror. In the infrared light, gold carries out better.
Whichs the surface layer?
Thats the surface area.
The innovation behind each of these hexagonal segments was developed specifically for the Webb Space Telescope, to make a large mirror that is light.
So the product of beryllium was picked to make the structure that you see under the gold covering.
And beryllium is extremely strong, really stiff. Its got good residential or commercial properties, when you cool it down, its stable, but at the very same time its a light material so we might make a big telescope that is not too heavy and can be released in area.
So you pointed out earlier a sunshield.
Yes.
Can we discuss the structure of the sunshield as well and its function?
Yeah, the sunshield is very crucial on this mission. It was extremely difficult to create such a big sunshield.
Five layers of special product as big as a tennis court.
Undoubtedly will not fit in any of the existing rockets, so it was developed to be in a compact configuration, folded around the main mirror at launch. That it could fit in the fairing of the Ariane 5 rocket.
And the reason its there, its because the Webb Space Telescope is optimized for observation in the near infrared, in the near and the mid-infrared part of the electromagnetic spectrum.
Thats the light that we cant see with our eyes?
Precisely, whichs the reason of the sunshield, to keep the telescope and the instruments, the scientific instruments always in the shade of the Sun and the Earth. Space is really cold, its minus 270 degrees (celsius), so by keeping the telescope constantly in the shade of the sun we can cool it down to extremely low temperature levels. Minus 220, 230 degrees celsius.
Truly cold. Which is fantastic to observe infrared light, since then we have an extremely sensitive instrument.
And how numerous detectors are on James Webb Space Telescope?
So there are four clinical instruments with different functions for different kinds of science that you can do.
NIRSpec the Near Infrared Spectrograph.
MIRI the Mid-InfraRed Instrument.
NIRCam the Near Infrared Camera.
And NIRISS the imager and spectrograph.
Okay. And what are you hoping that info will inform us about far-off galaxies, the early stars?
We see objects that are 13 billion light-years far from us. We expect to discover these.
So that indicates that were visiting items as they were 13 billion years earlier. These are very young galaxies, so we desire to understand what was going on there, what was the temperature level, what was the pressure, how numerous stars?
And we can do that with a spectograph. Precisely examining the light and after that find out how the galaxy formed by looking at these very young galaxies.
, if we come closer to house we can likewise look for circumstances at the atmospheres of planets.
.
Worlds in our planetary system, Jupiter, Saturn. Again with the spectrograph, we discover whats going on these planets.
And Webb will be looking at planets also?
Yes, worlds in our planetary system and likewise worlds that we call exoplanets which are worlds that orbit stars in other galaxies.
Do you think James Webb Space Telescope will help us find life on other planets?
That is a difficult concern.
Life per se? I think it would be difficult.
I think its not truly something really likely. But since of this capability of looking at the atmosphere of exoplanets. And also for instance the moons of Jupiter. I think we could discover a lot about whether the aspects are present that might sustain life.
So if we look at the planet thats in what we call the habitable zone, so at the best distance from its own star to have temperatures that are not insane cold or insane hot. Thats a temperature range that we think life could exist.
And after that we take a look at the environments and for circumstances we see that there is oxygen, there is water vapor, theres methane. That might offer us a tip that life is present or its possible on that world.
So thats extremely interesting.
Wow, Giovanna, thank you. That was a great deal of details but I believe it might be useful if we saw the design and went of the James Webb Space Telescope?
Yeah, sure, obviously.
Lets do that.
Lets go have a look at this model. Yes.
Wow. That is amazing.
Wow. Its rather excellent even at this size.
It is, its a really striking shape?
Giovanna thank you a lot for speaking with us today.
Its been a satisfaction.
Its actually motivating that a little girl who searched for at the stars in her hometown wound up working on the worlds most effective area telescope.
Its extremely amazing and I was very fortunate.
Thank you a lot.
Thank you, thank you for the chance to talk to you.
If youre trying to find more astronomy instructional resources, take a look at ESA Educations Teach with Astronomy web page. And keep an eye out for more videos originating from ESA Education.
