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The James Webb Space Telescope.
Named after the NASA administrator who oversaw the Apollo moon landings,
this space behemoth is the largest, most powerful and most complex space telescope ever built.
It has been hailed as the successor of Hubble, which itself was instrumental in expanding our
understanding of the universe over the last few decades. It has undergone major redesigns, cost
$9.7billion to build, and has taken 25 years to fully develop, construct and test. There
were moments in its decades-long construction where it was very nearly cancelled completely.
And yet with the aid of scientists from several nations around the world, it has overcome hurdle
after hurdle. But for all this, it will only last in space for a maximum of 10 years.
Why have scientists undertaken the construction of this telescope? Why put all of this time,
money and effort into building something that will be, relatively speaking, so short lived?
The answer is because this telescope, in a way unlike any before it,
will allow us to peer through time to the beginnings of the universe itself.
I’m Alex McColgan, and you’re watching Astrum. Join with me today as we explore
how this incredible spacecraft will allow scientists to pull back the curtain on the
first galaxies to come into existence after the Big Bang. Together we will discover the science
and engineering that went into it, as well as the challenges it faced. Because this truly
will be a spacecraft that will help us access clues to the universe’s origins like no other.
The James Webb Space Telescope first began in 1996. NASA at that time had for years
been considering a Next Generation Space Telescope to help them find the data they desired, and the
original plan was to make an 8m aperture telescope that would cost approximately $500 million.
However, as time went on, decision makers realised that far more resources would be needed to achieve
their aims. But what exactly were their aims? Well, the NGST was to be an infrared telescope.
Hubble had been functioning since 1990, but its primary range was the visible and ultra-violet
light spectrums. Although it had some infrared detection capability, this was somewhat limited.
And why do scientists want a powerful infrared telescope?
Well, this comes down to some fundamental facts about the universe itself.
Scientists believe the universe as we know it has existed for roughly 13.8 billion years. How it all
began is a fascinating question, and one that many have theorized over. Current mainstream theories
revolve around the idea of a “Big Bang,” where all matter existed in a space that was so small,
it was effectively zero. Atoms did not even exist at that stage - they would have been too large!
Suddenly, everything expanded outwards at once. Matter began to coalesce into atoms, then dust,
then stars and planets, and the universe has expanded and cooled ever since.
But wouldn’t it be helpful to be able to look back and see for ourselves those
first moments of creation, or the formation of those first galaxies?
That might give us insights into exactly how all of it happened. The JWST will either provide
evidence for the big bang, or completely change our theories thanks to the way light travels.
To a point, at least. While light is blindingly fast, it is not instantaneous. There is a tiny
time delay between when light is emitted, and when we see it. Photons, or particles of light, travel
at a constant rate. 299,792,458 m/s exactly. Our sun sits at a point 147.87 million km from us.
This means that it takes approximately 500 seconds for light to travel from it to us.
So, what you see in the sky right now is not the sun as it is, but the sun as it was 8 minutes and
20 seconds ago. This time delay becomes severe even when you consider things that are relatively
close to us. The next nearest star, Proxima Centauri, is so distant from Earth that it takes
4 years for its light to reach us. All of this means that for objects that are further and
further away from us, we would see it as it was further and further back in time. If there was
an object sufficiently far away, we would see it as it was 13.8 billion years ago, at the origin of
the universe. And fortunately, as some speculate, we exist in an infinite universe, so such far away
objects should in fact exist. With the James Webb Space Telescope, we hope to be able to see them.
But why does the JWST view in the infrared? Well, one reason is that infrared light tends to punch
through clouds of cosmic matter better, allowing us to see past otherwise opaque gas clouds to see
what lies on the other side. But the main reason, and the one that is relevant to seeing those early
galaxies, is because of a second quirk of the universe – the fact that space is expanding.
For reasons that we don’t fully understand, but which scientists currently theorise are the result
of dark energy, everything in the universe is moving away from everything else constantly.
As a star moves away from us, the light from it is stretched in a process known as the Doppler
effect. And because the wavelength of light is the part that defines what colour we see,
as light stretches, it shifts further and further towards the red half of the spectrum.
But this expansion isn’t constant. Scientists have observed that the further something is
away from us, the faster it is expanding away from us too. This means that light
from the furthest away galaxies has shifted so far into red that it has gone beyond it – into
infrared frequencies. Hubble was not fully designed to detect these frequencies. The JWST is.
JW’s receptors can detect light at frequencies from 0.6 micrometres to 28.5 micrometres long.
Interestingly, this means that it actually can’t see all visible light frequencies. It can see red,
and a large amount of orange frequencies, but nothing beyond yellow. Its focus lies in the
infrared frequencies. In this way, to say that the JWST is a replacement for Hubble is factually
incorrect. At NASA they prefer to say that the JWST supports and compliments Hubble. Each will
focus on frequencies of light that the other does not see so clearly. Besides which, as Hubble could
potentially last until 2040, it’s likely that it will outlast the JWST too, which would make
the JWST an odd replacement. Still, to see these infrared rays from such distant sources is a huge
challenge. If you and a friend each held a candle on a clear night and walked away from each other,
it wouldn’t be too long before your candles started to look dimmer to the other person. This
is because of the inverse square law, where light photons spread out with distance. Plus, light
tends to scatter when it passes through matter, and although space is extremely empty, there’s
enough particles of dust floating around that over the vast distances of space, objects that are far
away get more difficult to see. To combat this, the JWST houses a gold-plated Beryllium mirror
that is 6.5 m in diameter. This makes its surface area 6 times larger than that of Hubble’s mirror.
This larger mirror is designed to catch more light from distant sources before focusing it
back into the telescope’s instruments, allowing them to pick up fainter traces of radiation.
Furthermore, as the name suggests, the JWST is a space mirror. Being in space
means that the telescope does not have to contend with the Earth’s atmosphere, which can diffract
and distort light waves that pass through it. The vacuum of space provides a much clearer view,
allowing the JWST to find those tiny diffuse infrared waves much more easily.
The JWST will be orbiting the earth in a position known as the L2 Lagrange point. This position in
space is technically not a true orbit, but exists 1.5 million km from the Earth at the
point furthest away from the sun. For point of reference, the moon is 384,400 km from the Earth,
so this is much further out. Due to the way the Earth’s gravity interacts with the Sun’s,
this point of space is gravitationally stable, making it easier for an object to “hover” there
with minimal effort. This makes it an ideal viewing station for an orbital telescope.
One spacecraft was sent there already – the Planck space observatory. The distance from
earth is far enough away that the JWST does not have to contend with any radiation bouncing off
the Earth or the Moon, but is also close enough that it can send signals back to Earth telling
us what it sees. Naturally, at this position, it will be very difficult for us to visit the JWST.
So, although the JWST was designed with a docking ring, it is currently planned that there will be
no missions to the JWST to service or replace its parts once it is up there. Although it needs
minimal effort to maintain its position, minimal is not zero. The JWST has enough fuel to maintain
its position for at least 5 years, and at most 10. After that, it will decay from its orbit and will
no longer function. It has a guaranteed expiration date. One final benefit of this position, however,
is the temperature. Because heat travels in infrared waves, the heat generated by the
telescope’s own parts could potentially “blind” its own sensors if left unchecked. However,
thanks to its position in space the JWST will be able to cool itself to temperatures of -223 °C.
This is also aided by its solar shield. You have no doubt noticed the large silver canvas
at the bottom of the satellite. This 5-layered shield is the size of a tennis court, and is
designed to point in the direction of the sun, Earth and Moon to block heat coming from them.
With that last fact, you may have begun to realise the scale of this satellite.
It is vast, roughly 20 m x 14 m, and weighing almost 6,500 kg. This raises a question:
How are they going to get this telescope into orbit? Well, that is explained by one of the most
frankly astounding engineering aspects of this telescope – its capacity to fold up and unfold.
The Ariane V rocket that will carry the JWST into orbit has a 5 m diameter, but this is
not sufficient to fit the JWST. As such, the JWST has been designed so that its mirror can fold in,
as can its solar shield, reducing its total dimensions while it is in the rocket.
Once it has been launched and while it is traversing space to its Lagrange position,
the JWST will begin gradually unfurling in a delicate ballet. Arms will unfurl, shields will
unspool. The hexagons of the mirror will rotate into position, and then align themselves with
the aid of tiny motors until they are perfectly flush with each other, all to allow it to go about
its incredibly delicate business of gathering radiation from the dimmest lights in the sky.
Mastering this process of getting such a sensitive device into orbit without something breaking
is the reason the JWST has taken so long to build. Remember, once launched,
there is no chance of going up there and fixing it. If something broke during deployment,
it could spell the end of the entire mission, wasting over 2 decades of work and $9.7 billion.
In 2005, just a few years before the initial intended launch date, the entire project underwent
a fundamental redesign. Everything was checked and double-checked by review boards. In 2018,
the project was further delayed when a test of deploying the solar shield ended with it ripping.
A review of what went wrong found an additional 344 potential single-point failures, any one of
which breaking would mean that the entire thing would no longer work. When costs started rising in
2011, the American Congress moved to reduce NASA’s budget as a way of cancelling the JWST. However,
the public backlash in support of the project ultimately led them to reverse their decision.
The JWST was built by NASA in cooperation with the European Space Agency and the Canadian Space
Agency. It has been delayed over 13 times. Its project costs have increased from $500 million to
$9.7 billion. But finally, very soon, it will be here. Its mission to peer into the heart of space,
and uncover the mysteries of the formations of the first galaxies, stars and planets, will finally
begin. You can bet that when it finally launches from the European Space port in French Guiana,
there will be plenty of people waiting for news of a successful launch with bated breath.
And you can also bet that once it’s in the sky, scientists will be fighting
tooth and nail to get a chance to look through it, and to discover what wonders it sees.
So, good luck for the launch and the deployment to all the teams involved with this. If it works,
with instrument will be the biggest thing for space science for potentially decades to come.
Now, James Webb should launch this year, but you might want to keep checking the
news for the latest updates. One way I stay up to date with the goings on in the world,
is this pretty handy resource called Morning Brew, which is a completely free email newsletter that’s
sent to your inbox 7 days a week. It covers all things business, finance and tech, and
also covers space if anything exciting is going on. With today’s Morning Brew, I found out that
the Japanese billionaire has now made it to the ISS on the first tourist trip there for a decade.
It’s great to browse, as the newsletter is concise yet still has an element of charm to it,
it’s not super dry like typical news summaries. If there is something you want to know more
about in depth, there’s links throughout that take you to full articles on news websites.
It takes less than 15 seconds to subscribe, so why not give it a go?
If this is something you would like to check out further, find the link in the description below.
Thanks for watching! If you enjoyed this video,
check out my other telescope video I made on ESO’s upcoming ELT,
which is a really exciting project. Thanks to my patrons and members for their support,
if you want to support too, check the links in the description. All the best, and see you next time.