This is the golden eye of the James Webb Space Telescope. Unparalleled in scope and scale,
Webb is the largest telescope to ever launch into space. It's a little bit like our generation's
Apollo in that it was very challenging to build but the payoff is also very large. This
is about as powerful as it gets. This is an extremely ambitious project. We developed
all these new technologies that didn't even exist, but we needed it to carry out the science.
An international project like this that has countless firsts takes time, but the
painstaking effort to design, construct and test Webb’s optical system will be worth
the wait. Overnight, the eye of the telescope will revolutionize our understanding of the
cosmos and be set loose on the biggest questions in astronomy.
I've been working on the James Webb Space Telescope for 20 years.
When I first started, we really didn't even know
exactly what the design would look like, what materials we would make the mirrors out of,
how many segments the telescope would be. We actually had to invent multiple technologies.
That's because the astronomical community was after something that hadn’t been observed before…
the early universe. The first stars and galaxies started to form 100 to 250 million years after
the Big Bang, around 13.6 billion years ago. Because the universe is expanding,
the visible light from the early universe gets stretched into the infrared and that's called a cosmological
redshift. It's this cosmological redshift that Webb's optics will be hunting for, to
uncover the story of the early universe. Infrared light can pass through dust in the universe.
And so it allows us to peer through dust clouds and see, for example, stellar nurseries
No other telescope today has the collecting power and sensitivity that NASA’s JWST has to
lift the veil on the universe’s secrets. The James Webb Space telescope is sensitive
enough that if there were a bumblebee at the distance of the moon, we would be able to
detect it. The telescope’s core superpowers come from its advanced optical system. James
Webb’s eye, otherwise known as the Optical Telescope Element, consists of four ultra
reflective golden mirrors and dozens of subsystems to support the massive optics. The first thing
you recognize is the gold mirrors. There's a reason why we chose gold is because
it has a very high reflectivity in the infrared. Out of the four mirrors, it’s the primary
one that really stands out. That's the first mirror that light hits. And in this case we
have 18 segments that are hexagonal shaped. Which means each mirror actually acts as a
separate telescope until they’re aligned in space to work as one. All of the 18 hexagonal
segments and additional mirrors are made of beryllium, a strong and lightweight metal
that holds its shape at cryogenic temperatures. Remember, space is a balmy -270° C. The other
subtlety of it all is because it's infrared, the mirrors have to be cooled to very cold
temperatures so that they don't produce heat in the form of infrared light that would contaminate
the images. And lastly, a large telescope gives you resolution. The resolution goes
with the diameter of the primary mirror. Webb’s primary mirror is 6.5 meters in diameter,
which gives the telescope more than 6 times the collecting area of the Hubble Space Telescope!
It's a lot like collecting raindrops and the bigger the bucket, the more raindrops you
collect. And when you're trying to see the very early universe, which is very dim, you
need to collect a lot of photons. For the engineering team, it’s easier to look back
at what was achieved when you’re at the finish line. So many aspects of the telescope
needed to be invented before manufacturing began years ago, from the segmented beryllium
mirrors to the large sunshield for keeping the system cold, to algorithms— lots and
lots of brand new algorithms for keeping the mirrors aligned 1.5 million kilometers away.
In terms of a science mission like this, this is the largest, most ambitious one that NASA
has ever taken on. And it's arguably one of the most complicated, but also powerful ones.
That’s because to see the universe like never before, it requires a new type of observatory.
For the JWST team, building that observatory meant constructing a complex cascade of mirrors
that can focus light down like no other telescope before it. The first mirror is the primary mirror.
That's what initially collects the light from the distant universe,
the light then converges down to a secondary mirror
and the secondary mirror continues to focus the light and then that reflects light to
what we call the tertiary mirror. And then finally, the light is sent to a fourth mirror,
which is the fine steering mirror. And the purpose of that mirror really is to correct
slow drifts between the telescope and the spacecraft. After all that, an image is created
as the light enters the four science instruments. We call them science instruments, but you can
think of them as cameras. They each have their own detector which actually collects the light,
like the detector on your camera. The light photons get converted into electrons.
They get recorded onto a data recorder on the telescope. And then the data actually
gets sent back down to the earth using the deep space network. And once we have the first
completed images, the long wait... will have ended. So space telescopes are like time machines
in a sense. They can take us back and collect these photons that were created at the very
beginning of the universe. That light is always there. It's always coming down, we just haven't
had the capability. Until now. In the first year of operations, Webb’s mirrors will
collect light from early galaxies and stars, the environment around black holes, supernovae,
and other space phenomena with greater sensitivity than ever before. And of all the highly anticipated
observations one is a personal favorite for Michael. I'm really excited about the exoplanet
discoveries. We know of over 4,000 exoplanets orbiting other stars. But we don't really
have an understanding of what their compositions are. And that's one of the key aspects of
the Webb mission. For the first time, we'll really get a good understanding of their properties,
and those are very fundamental features for understanding how they formed, how
they evolved and also will give us some insight as to the habitability of these exoplanets,
whether there might be liquid water where life could exist. By searching for the building
blocks of life elsewhere, it can give us insight into how life began on our own pale blue dot.
Webb’s science mission touches on so many fundamental questions in cosmology that it
holds the promise of rewriting and expanding our textbooks for years to come. Every time
we have a transformative increase in observing capability like Webb, there's just tremendous
scientific discovery. We used to use the phrase early when we were developing Hubble, expect
the unexpected. And I think here, you can almost say, expect the unexpected squared.
The James Webb Space Telescope is a new kind of telescope, it's never been done before.
This is really new terrain for NASA and for the world. And setting a stage for future
telescopes that are scalable to larger sizes. Which means if we ever want to see
a pale blue dot around another star, the foundation has been set.