It’s almost as if, right from the start, we felt as though the stars were important and that we
were somehow connected to them. For thousands of years, we have looked to the night sky as a source
of wonderment and inspiration. By watching the daily motions of the Sun, the changing
phases of the moon, and the stately, predictable, nightly procession of the stars across the sky,
we learned how to tell time and how to create calendars in order to regulate our lives. We
used the stars as familiar guideposts to help us navigate both land and sea. We created patterns
among them to represent the gods and heroes of our various mythologies and we also gazed into the
ink-black darkness and asked some of the oldest and most fundamental questions of all: “where did
we come from?”, “is the universe eternal, or did it have a beginning?” and “are we alone?”
Hello everyone, I’m Darrell Heath, the NASA Outreach Coordinator for the Arkansas
Space Grant Consortium located on the campus of UA Little Rock, welcome to The Night Sky.
Due to the finite speed of light, whenever we look out into space we are also looking back
in time. This means that whenever we look at celestial objects, we do not see them as they
are right this minute, we always see them as they were at some point in the past. Looking
at the moon? You are seeing it not as it is right that very moment, you are instead seeing it as it
was 1 and 1/3 seconds ago. The Sun? Well, let’s just say that if it stopped shining
(and it won’t, for now anyways) you wouldn’t know about it for 8 minutes and 20 seconds.
The further a telescope can see, the further back in time we can peer. With our best telescopes, we
can see billions of years into the past and from these observations, combined with the knowledge
that the universe is expanding, it becomes obvious that the universe was not created “as is”,
instead, it must have evolved over time, from the simple, to the complex to become the universe
we see today. The so-called Big Bang Theory is the best working model that astronomers now have
for providing a scientific explanation for the origin and evolution of the universe. According to
current evidence, the universe had its beginning some 13.77 billion years ago from a very dense,
very hot, and very tiny state. For reasons we do not yet understand, this very compact and very hot
singularity suddenly expanded in size and, in doing so gave it rise to all of space,
time, matter, and energy. But the early universe was far too hot for atoms to exist. Initially,
there was just a hot, dense soup of sub-atomic particles. With time, the universe would cool down
to a point where the first atoms could appear and the first elements, primarily hydrogen and helium,
came into being. Sometime after that, the first stars and galaxies would appear.
One of the holy grails in astronomy is to be able to see these first stars and galaxies and
we now have the means to accomplish this with the NASA and European Space Agency’s
James Webb Space Telescope. The telescope is named for James E. Webb,
NASA’s second administrator. He spearheaded the Apollo program and initiated numerous
space science programs, leading to more than 75 launches during his tenure.
Development on the James Webb Space Telescope (or the JWST; or simply “Webb”) began in the
late 1990’s with a projected launch date in 2007. But, due to a variety of reasons, ranging from
budgetary issues to technological issues, and to the pandemic, things got delayed. Then again, we
have never sent a telescope like Webb into space before. It’s huge for one thing. The Hubble Space
Telescope is about the size of a school bus with a primary mirror that’s nearly 8ft in diameter. The
JWST is about 70 ft long (half the size of a 737 aircraft) and its primary mirror is a whopping 21
ft in diameter. In fact, the mirror is so big that it is made to be foldable, origami style,
so that it will fit within the 5.5-meter-wide rocket that will carry it into space. The mirror
is actually 18 individual segments, made from the rare metal beryllium and coated with a layer of
ultra-thin gold about 1000 atoms thick in order to enhance the mirror’s reflectivity to infrared.
But why does the Webb’s mirror need to be this big? And what’s so important about infrared light?
The most important job of any telescope, whether it uses glass lenses or highly polished mirrors,
is to collect light from very distant and, often times, very faint objects. How much
detail a given telescope can provide depends on how much individual photons of light it can
gather. A good analogy would be like how a bucket can gather individual drops of rainwater. So,
Webb’s huge mirror means that it is a light bucket of enormous proportions and enormous potential.
The Webb’s larger primary mirror allows it to collect much more light than Hubble can,
effectively allowing it to see further back in time than any telescope now available. The
James Webb Space Telescope will be a giant leap forward in our quest to understand the universe
and our origins. The telescope will examine every phase of cosmic history: from the first luminous
glows after the Big Bang to the formation of galaxies, stars, and planets to the evolution
of our own solar system. Viewed this way, Webb is not so much a replacement for the Hubble
as it is an extension to the many discoveries made by everyone’s favorite space telescope.
As I mentioned earlier, Webb’s emphasis will be primarily in detecting light in the longer,
infrared wavelengths. What’s so important about infrared? Well, the light emitted by those first
stars and galaxies all those billions of years ago, would almost certainly have been within
the visible portion of the electromagnetic spectrum, but that’s not how we would see them
today. Remember, the universe has been expanding ever since the Big Bang. And when I say that
the universe is expanding, what I mean is that space-time itself is stretching and all of the
stars and galaxies are riding along with it. Think of a lump of raisin bread dough (mmm,
raisin bread). Anyways, those raisins are the stars and galaxies.
At first, embedded within the dough, those raisins are fairly close together but,
pop it in the oven and the dough rises and the raisins move apart from one another.
It’s important with this analogy to realize that it’s not the raisins that are being
stretched apart, it’s the space-time dough matrix in which they are embedded that is.
All of this is perfectly compatible with Albert Einstein’s General Theory of Relativity.
As those ancient stars and galaxies recede away from us, the light that they emit gets
stretched into longer, low energy, redder wavelengths. Given the vast amounts of cosmic time
since those first stars and galaxies came into being, that light is now only detectable to us
within the infrared region of the electromagnetic spectrum. Exactly what the universe's first light
from the first stars looked like, and exactly when these stars formed is not yet known.
These are some of the questions Webb was designed to help us answer.
So, is that all Webb can do? Oh no, its capabilities include much more.
With its infrared eyes, Webb will be able to see right through and into
massive clouds of dust that are opaque to visible-light observatories like Hubble,
where stars and planetary systems are being born.
Take a look at the Pillars of Creation, one of Hubble’s most famous images. What you are
looking at is just a small part of a much larger cloud of gas and dust known at the Eagle Nebula,
located some 7,000 light years away in the constellation of Serpens.
This cloud of gas and dust is what’s known as a stellar nursery, a place where new stars are being born.
In this image, Hubble is showing the Pillars in visible light, but what we want is to be able
to peer inside those clouds and see what’s going on. Unfortunately, the gas and dust is
impervious to visible light. The good news is that Hubble has limited infrared vision
and infrared light is able to penetrate through the surrounding dense clouds of cold gas and dust.
Now, take a look at the Pillars in infrared. Look at all of the stars that we were unable to see
before! In this image, Hubble was able to see the heat, or infrared light, those newborn stars are
emitting but was kept hidden to our eyes from the cooler dust clouds. Now just imagine what
Webb will be able to see with its much sharper infrared eyes. We will be able see inside these
dusty cocoons in order to learn the secrets of the creation of new suns and their planetary families.
And if that doesn’t float your boat, then check your pulse. But I’ve saved my favorite
Webb capability for last. With the James Webb Space Telescope, we may finally learn
whether or not we are alone in the universe.
Right now, we know of the existence of more than 4,000 exoplanets, alien worlds orbiting stars
other than our own Sun. Thousands more are awaiting confirmation. Webb will be equipped
with spectrometer, a standard part of the astronomer’s toolkit. A spectrometer allows
us to analyze the light from objects and part of the information we can glean from such analysis
is the chemical makeup of whatever it is we are looking at.
In the case of exoplanets,
Webb can watch whenever one passes in front of its parent star. As the exoplanet does so,
Webb can capture the light being filtered through its atmosphere and this can tell
us what gases are present. It might just well be that we can pick up chemical biosignatures
that would indicate the possible presence of life. Confirmation of life beyond Earth would be one of
the most important scientific discoveries of all time and I hope to see the day when it happens.
The James Webb Telescope will be launched in October of 2021. However, the Webb will have many
hurdles to overcome.
NASA is crosschecking every component before launch to make sure all is well.
If the mirror or protective sunshield does not deploy correctly, or if any other bit
of tech goes awry, there will be no way to fix it. In order to escape
the infrared heat from the Earth, the telescope will be put into orbit some one million miles
away. But if it all goes to plan, you can expect Webb to make discoveries that will change
our most fundamental understandings of the universe and our place within it.
Before I go, I just want to let you know that if you are a formal or informal educator,
and you want to incorporate some of the science of the James Webb Space Telescope
into your lessons or programs, please visit the JWST’s web site at the link you see here:
https://www.jwst.nasa.gov/index.html
Not only do you get a great overview of the scope and its mission,
there are also a wide assortment of lesson plans and activities
for every age group. It’s great content and it’s all free so please make use of it.
Until meet again, take just a little bit of time to step outside and look up,
in both awe and wonder.