The James Webb Space Telescope will be 100 times as powerful as the Hubble.

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https://www.vox.com/science-and-health/22664709/james-webb-space-telescope-launch-date-december-science-hubble


The largest space telescope in history is about to blow our minds

The James Webb Space Telescope will be 100 times as powerful as the 
Hubble. It will change how we see the universe.

By Brian Resnick@[email protected]  Sep 22, 2021, 9:30am EDT

Exploring strange new worlds. Understanding the origins of the universe. 
Searching for life in the galaxy. These are not the plot of a new 
science fiction movie, but the mission objectives of the James Webb 
Space Telescope, the long-awaited successor to the Hubble Space 
Telescope. NASA is building and launching the Webb in partnership with 
the European Space Agency and Canada.

The launch, which will propel the Webb to nearly a million miles away, 
is now scheduled for December 18, 2021. When it fully deploys in space, 
the Webb will usher in a new age of astronomy, scientists say, and show 
humanity things it has never seen before.

“The Webb represents the culmination of decades, if not centuries, of 
astronomy,” says Sara Seager, a planetary scientist and astrophysicist 
at MIT. “We’ve been waiting for this a very long time.”

Scientists started thinking about a follow-up even before the Hubble 
Space Telescope launched in 1990. After more than three decades in 
space, it’s unclear how much longer this boundary-breaking satellite 
will be able to scan and photograph the universe.


The Webb was originally supposed to launch in 2010 and cost around $1 
billion. Its price tag has since ballooned to $10 billion, and it’s way 
overdue. But the wait will be worth it, at least according to the 
scientists who expect new and revealing glimpses of our universe.

“We’re going right up to the edge of the observable universe with Webb,” 
says Caitlin Casey, an assistant professor of astronomy at the 
University of Texas at Austin. “And yeah, we’re excited to see what’s 
there.”

The Webb will surpass the Hubble in several ways. It will allow 
astronomers to look not only farther out in space but also further back 
in time: It will search for the first stars and galaxies of the 
universe. It will allow scientists to make careful studies of numerous 
exoplanets — planets that orbit stars other than our sun — and even 
embark on a search for signs of life there.

The Webb is a machine for answering unanswered questions about the 
universe, for exploring what has been unexplorable until now. Here’s a 
guide to what the Webb is capable of.

The Webb’s golden mirror is a giant leap for telescopes of its kind

These are two Hubble images of the Pillars of Creation. The right shows 
what it looks like in infrared, which is closer to what the Webb 
telescope will see. NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. 
Nota (ESA/STScI), and the Westerlund 2 Science Team

The launch of the Hubble Space Telescope, named after famed astronomer 
Edwin Hubble, was itself a huge leap forward for astronomy. Here on 
Earth, astronomers seek out remote mountaintops and deserts to build 
major telescopes for the best chance of viewing a dark sky away from 
pollution and bright lights. But their view is still marred by the 
slight haze and luminescence of the Earth’s atmosphere. Space is “the 
ultimate mountaintop,” as NASA explains. There’s no better view of space 
than the one from, well, space.

Hubble has meant so much during its 30-year run. For one thing, it’s 
sent us unforgettable, jaw-droppingly beautiful images like those of the 
Lagoon Nebula and the Pillars of Creation.

The Hubble Space telescope captures the Lagoon Nebula in 2018. NASA, 
ESA, and STScI

It’s also taught us about the age of the universe, about what happens 
when stars explode, about black holes. It helped establish many of the 
boundaries that the Webb hopes to push. Most powerfully, its 
observations have led scientists to believe the universe is expanding at 
an accelerating rate, propelled by something so mysterious that 
scientists simply call it “dark energy.”

The Webb, named for the man who led NASA in the decade leading up to the 
moon landing, is set to take all this a step further. “What we’re going 
to get is a telescope that’s about 100 times more powerful than Hubble,” 
says Amber Straughn, an astrophysicist at NASA who works on the Webb.

Webb Telescope and Hubble Telescope primary mirror comparison with 
person as reference. Michael McClare/Aaron E. Lepsch/Krystofer Kim via 
NASA’s Goddard Space Flight Center
How?

The Webb improves on Hubble in two key ways. The first is just its size: 
Hubble was about the size of a school bus, whereas Webb is more like the 
size of a tennis court. “This thing is enormous,” Straughn says. “Webb 
is by far the biggest telescope NASA’s ever attempted to send into space.”

But it’s not just the total size of the contraption that matters. When 
it comes to reflecting telescopes, the key component is the size of its 
curved mirror. “You could sort of think of a telescope mirror like a 
light bucket,” Straughn says. The more light you can collect in this 
bucket, the fainter and farther-away things you can see in the universe.


Hubble’s mirror was an impressive 7.8 feet in diameter. Webb’s 
beautiful, gold-hued mirrors combine for a diameter of 21.3 feet. 
Overall, that amounts to more than six times the light-collecting area.

A drawing of the Hubble mirror beside the Webb mirror, with a person for 
reference. The Hubble mirror is smaller.
NASA
What does that mean in practice? Well, consider one of Hubble’s most 
famous images, the Deep Field. In 1995, scientists set the Hubble to 
stare off into a teeny-tiny patch of sky (about the size of the head of 
a pinhead, held at arm's length from the viewer) and capture as much 
light as it could from that one spot.

The image that came back was astounding. Hubble uncovered thousands of 
galaxies in this teensy patch of sky, helping us refine the number of 
galaxies thought to exist in the universe.


The Hubble Deep Field image shows that even in a tiny patch of sky, 
there are thousands of galaxies. NASA, ESA, R. Bouwens, and G. Illingworth
This photograph also revealed Hubble’s larger power — as a time machine. 
In astronomy, the farther away things are, the older they are (because 
light from faraway places takes a very long time to travel to Earth). 
That means this Hubble Deep Field is not only a snapshot of space: It 
also contains the history of our universe. Galaxies in this image appear 
to us as they were billions of years ago.

“What Webb will do is take that field and go even further,” UT Austin’s 
Casey explains. “So the tiny specks of light in the background of the 
Hubble Deep Field will brighten and become more detailed, we’ll be able 
to see spiral arms, we’ll be able to see structure, and then we’ll get 
more specks of light even further in the past. We’re seeing farther back 
in time with Webb.”


With Webb, astronomers like Casey will be able to see so far back that 
they’ll potentially spot the very first stars and galaxies. Hubble has 
seen light dating to about 400 million years after the Big Bang, which 
took about 13.3 billion years to reach us.

“That’s far! But Webb has the capability to take us to 250 million years 
after the Big Bang,” explains Casey, who has been approved to work with 
the Webb Space Telescope. “It might not sound like a big difference. 
What’s a few hundred million years between friends? Actually, it’s the 
difference between seeing the first stars that ever turned on [and] 
arriving a bit too late after the funeral.”

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Beyond that are barriers through which even the Webb cannot see. Prior 
to the first starlight, the universe was shrouded by a “dense, obscuring 
fog of primordial gas,” as the National Science Foundation explains. 
There’s no light that reaches our telescopes from this time, which is 
called the cosmic dark ages.

(There is some background radiation from the Big Bang called the cosmic 
microwave background, a faint glow that shines to us from before the 
dark ages. But for the most part, the dark ages is a blank spot in our 
timeline of the universe.)

Casey and other astronomers hope the Webb will help them understand the 
end of the dark ages and figure out what caused this fog to lift. 
Scientists suspect the starlight from the earliest galaxies did it.

“If you have a cloud of gas and it encounters energetic light, that 
energetic light will ionize that gas and disassociate that cloud,” Casey 
says. “And so if that light just has turned on, it then hits that gas 
and really transforms the entire universe from a dark place to a light 
place.”

The Webb telescope sees infrared light — which can be very, very old

The James Webb Space Telescope under construction in 2016. NASA/Chris Gunn
The Webb’s other advantage is the type of light it collects.

Light comes in a lot of different varieties. The human eye can see only 
a narrow band known as visible light, but the universe contains lots and 
lots of light outside this range, including the higher-frequency, 
higher-energy forms: ultraviolet, gamma rays. Then there’s the 
lower-energy light with longer wavelengths: infrared, microwaves, radio.


Hubble could observe a little bit of infrared light, but Webb takes it 
much further. NASA and J. Olmstead (STScI)
The Hubble Space Telescope collects visible light, ultraviolet, and a 
little bit of infrared. The Webb is primarily an infrared telescope, so 
it sees light that’s in a longer wavelength than what our eyes can see. 
This seems nerdy and technical, but it’s actually what allows Webb to 
look further back in time than the Hubble.

Infrared light is often very old light, due to a phenomenon call 
redshifting. When a light source is moving away from a viewer, it gets 
stretched out, morphing into a longer and longer wavelength, growing 
redder. (The opposite is true as well: As a light source grows closer, 
the wavelengths shorten, growing bluer.) It’s similar to what happens 
when a siren goes by: The pitch increases as the siren approaches, then 
decreases as it trails away.


Because space is constantly expanding, the farthest things away from us 
in the universe are moving away from us. “And as light travels through 
space from those distant galaxies, the light is literally stretched by 
the expansion of space,” Straughn says.


As the universe expands, it stretches the wavelengths of light along 
with it, a process called redshift. The farther away an object is, the 
more the light from it has stretched by the time it reaches us. 
NASA/JPL-Caltech/R. Hurt (Caltech-IPAC)
Imagine a star that’s really far away. The light from that star may 
start off in the visible spectrum, but it gets stretched on its journey 
to us. It grows redder and redder. “So when we see distant galaxies with 
Hubble, they’re sort of these little, tiny red nuggets,” Straughn says. 
Eventually, these very distant, old galaxies grow so red that they drop 
into the infrared spectrum. Webb can see this ancient light that has 
become invisible to the human eye.

Conveniently, infrared light has other uses as well. It’s a really good 
type of light to use to look at exoplanets. For instance, if you were on 
a planet that orbits another star and wanted to see Earth, visible light 
wouldn’t be your best bet.

“The Earth peaks in the infrared,” says Johns Hopkins Applied Physics 
Laboratory astronomer Kevin Stevenson, who plans to use the Webb in his 
research. So if we want to be able to study an Earth-like planet in 
another solar system, “What we really want to do is observe at infrared 
wavelengths, because that’s where the light from the Earth is being 
emitted.”


Exoplanet scientists like Stevenson are going to use the Webb to analyze 
the atmospheres of these worlds: The Webb is capable of determining some 
of the chemicals in their atmospheres. “We can detect water, CO, CO2, 
methane,” Stevenson says. While those aren’t definitive signs of life on 
their own, they could begin to ask fascinating questions: What created 
that methane and carbon dioxide? Could it have been life?

“We all want to find another Earth, don’t we?” Stevenson says. “The 
prospect of answering the question ‘are we alone?’ has been something 
that we’ve been asking ourselves for centuries. And I think with James 
Webb, this will provide us the first opportunity to really answer that 
question.”

This $10 billion gadget better not break
Scientists are clearly raring to go, but the Webb revolution has taken a 
while. One reason for all the launch delays to the launch has to do with 
contractor snafus. But a big source of all of them, NASA’s Straughn 
says, is the complexity of the Webb itself.

“Because it’s so big, there aren’t any rockets that are big enough to 
launch it fully deployed,” Straughn says. The telescope has to be folded 
up to fit inside a rocket, and has to deploy itself in space. “So that 
whole process of building a deployable telescope in space is the source 
of a lot of the engineering challenges.”

Upping the stakes is the fact that while Hubble was launched to around 
340 miles above the Earth, Webb will be almost a million miles away — 
four times the distance from the Earth to the moon.

That means once the Webb is launched, it will be unserviceable by human 
hands if it breaks. That’s scary, considering the history of the Hubble. 
Shortly after the Hubble launched in 1990, engineers realized there was 
a problem with its mirror; the telescope’s initial images came back 
fuzzy, and astronauts had to launch a space shuttle to fix it. That 
won’t be possible with the Webb. It just has to work.

It will be far away for good reason. Because Webb is an infrared 
telescope, it needs to be kept cold. The Earth itself is warm and glows 
in infrared. “Anything warm glows in infrared light,” Straughn says. “If 
the telescope was warm, it would just glow and see itself.”


James Webb Space Telescope orbit as seen from above the Sun’s north pole 
and as seen from Earth’s perspective. Michael McClare/Aaron E. 
Lepsch/Josh Masters via NASA’s Goddard Space Flight Center
Remarkably, any scientist around the world can apply to use the Webb 
Space Telescope, provided they write up a project proposal that passes 
peer review. It’s pretty competitive. Last year the Space Telescope 
Science Institute, which operates space telescopes from John Hopkins 
University in Maryland, put out a call for proposals for Webb’s first 
observing run. About a quarter of the proposals were accepted.

“It feels like part of me is still stunned,” says Lisa Dang, a physics 
PhD student at McGill University who was one of the lucky few to get 
approved to use the Webb. “And the other part is having this imposter 
syndrome — like, these data better be really amazing.”

Dang is set to study one of the most extreme planets ever discovered: 
K2-141 b, a planet 202 light-years from Earth and so close to its host 
star that its surface is believed to be covered by an ocean of lava. If 
it has clouds, they are likely made out of vaporized rock, which could 
then precipitate out “rock rain.” Not much is confirmed about this lava 
planet, but Dang will use the Webb to study its atmosphere and see 
what’s possible on this extreme world.

Winning the project proposal “made me feel like an astronomer for the 
first time,” Dang says. “But it also makes K2-141 b very real suddenly.”

This is the power of an unprecedented telescope such as the Webb. It 
will help astronomers like Dang fill in the blank spaces of the cosmos.

“It’s wild, when you think about it, that we’re able to piece together 
the history of what happened before the Earth or the sun even existed,” 
Casey says.

If all goes according to plan, these kinds of breakthroughs could come 
in a matter of months. Astronomers around the world are waiting for the 
countdown to begin.


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