The James Webb Space Telescope: Science on the Edge By NASA’s Amazing Space reporters December 2015

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IMAGE: NASA, ESA, CXC, the University of Potsdam, JPL-Caltech, and STScI

THE JAMES WEBB SPACE Telescope promises to

open up new horizons as

we gaze to the edges of the visible

universe. Webb is an infrared

telescope, seeing in a wavelength

of light difficult to observe from

Earth. It will be larger than any

space telescope ever placed in

orbit. The telescope will function

at temperatures just tens of

degrees above absolute zero — the

temperature at which even atoms

are so cold they cannot move.

Its launch in 2018 will help

astronomers answer some of

the most pressing questions in

astronomy, such as, How did the

first galaxies form? How do stars,

galaxies, and planets come into

existence? Are we alone

in the universe?

Envisioning the Webb telescope in operation: This illustration shows the James Webb Space Telescope observing a vibrant star-forming region, called N90, in the Small Magellanic Cloud, one of our Milky Way galaxy’s closest galactic neighbors. The Hubble image of the star-forming region is a blend of observations taken in X-rays and visible and near-infrared light. Infrared light sees through the dust that blankets star-forming regions to uncover the glow of young stars that cannot be seen in visible light. The Webb telescope will peer deeper into this dusty stellar nursery, revealing information about the material that comes together to form new stars and planetary systems.

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A P U B L I C A T I O N O F N A S A ’ S “A M A Z I N G S P A C E ” E D U C A T I O N P R O G R A M

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Infrared light is invisible to our

eyes, but not to Webb’s powerful

instruments. Orbiting 1 million miles

from Earth, the Webb telescope

will peer back to the time when

new stars and developing galaxies

first began to light up the universe

billions of years ago. Webb will see

light from the early universe that has

been stretched as it travels across

the expanding fabric of space. It

will see through clouds of dust to

the warm, infrared-emitting objects

hidden within. Our view of the

universe will expand as Webb gazes

on previously unexplored territory.

Why an infrared telescope?

Infrared is light beyond the red

end of the visible-light spectrum.

It is invisible to the human eye.

However, if we can detect it using

special instruments that observe

infrared light, we gain valuable

information about the workings of

the universe.

Astronomers prize infrared light for

several reasons.

First, the expansion of the universe

causes all galaxies to move away

from one another. Visible light

from the most distant objects gets

stretched as it travels through space,

turning into infrared light. To see

the farthest and earliest galaxies in

the universe, astronomers have to

look at the stretched, once visible

light that reaches Earth in the form

of infrared light.

Second, infrared light penetrates the

dark clouds of dust present in the

universe. Everything gives off some

infrared light, but warm objects —

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These Hubble Space Telescope images show striking differences between the visible-light and near-infrared-light views of a star-making pillar of gas and dust, called the Horsehead Nebula. The nebula appears as a solid dark structure in the visible-light image above. The bright area at the top left edge is a young star still buried in its nursery of gas and dust. The entire top of the nebula is being sculpted by radiation from a grouping of massive stars located out of Hubble’s view.

In the near-infrared image below, the Horsehead appears more transparent because infrared light penetrates gas and dust to reveal details not seen in the visible-light view. The star that was buried in gas and dust in Hubble’s visible-light image glows brightly in the near-infrared view. A rich tapestry of Milky Way stars and distant galaxies also appear in the infrared image.

IMAGE: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

IMAGE: NASA, NOAO, ESA, and the Hubble Heritage Team (STScI/AURA)

Two views of the Horsehead NebulaVISIBLEVISIBLE

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IMAGE: NASA/JPL-Caltech/R. Kennicutt (Univ. of Arizona)/Digitized Sky Survey

IMAGE: NASA, ESA, S. Beckwith (STScI), and the Hubble Heritage Team (STScI/AURA)

Above is an image of the Whirlpool galaxy (M51) taken in visible light by the Hubble Space Telescope. The image is an excellent example of a spiral galaxy, a rotating windmill-like structure of arms. The outer parts of the arms spin more slowly than the central parts, giving the arms a curved shape. One arm at the top of the image is particularly stretched because it is feeling the gravitational tug from the second galaxy passing behind the Whirlpool.

Below is the infrared view of this same galaxy, taken by the Spitzer Space Telescope. The infrared image reveals the galaxy’s dustier, star-forming regions, which are obscured from Hubble’s view. The James Webb Space Telescope will see into these regions with seven times the resolution and hundreds of times the sensitivity of Spitzer, revealing individual stellar nurseries and star clusters that are normally detectable only in our own Milky Way.

Two views of the Whirlpool galaxy

VISIBLEVISIBLE

NEAR-INFRAREDNEAR-INFRARED

Hubble Ultra Deep Field in near-infrared light: The Hubble Space Telescope image above reveals thousands of galaxies in one of the deepest views ever taken in near-infrared light. The image shows galaxies in a variety of shapes, sizes, and colors. The faintest and reddest objects are galaxies that existed about 12.9 billion to 13.1 billion years ago, when the universe was young. Many of these galaxies cannot be seen in visible light because the light is stretched to infrared wavelengths by the expansion of space.

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IMAGE: NASA, ESA, G. Illingworth and R. Bouwens (University of California, Santa Cruz), and the HUDF09 Team

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those at room temperature — emit

large amounts. We see this effect

on Earth. Night-vision goggles

rely on infrared vision to form an

image of warm bodies. Certain

snakes also detect their prey with

infrared-sensing organs. Dust clouds

block visible light, but not infrared

light. By detecting infrared light,

astronomers can see through the

clouds to the warm objects within.

Third, some things mostly emit

infrared light. Not all objects glow in

visible light, but even the dimmest

objects give off some infrared light.

Older planets, dust around stars, the

early stages of star formation, and

clouds of dust drifting in space are

all visible in infrared light. In many

cases, they are easier to spot in the

infrared than in visible light.

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IMAGE: NASA, ESA, and A. Feild (STScI)

This illustration shows a ring of debris surrounding the star Fomalhaut, located 25 light-years from Earth. A planet, called Fomalhaut b, may be orbiting just inside the ring. Hubble Space Telescope images of Fomalhaut b are among the first visible-light views of a planet outside our solar system. Astronomers estimate that the possible planet is no more than three times the mass of Jupiter.

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By studying the universe with

Webb’s infrared vision, our

understanding of space and

our place in the universe will

be reshaped by the telescope’s

discoveries.

Massive stars in the early universe

The universe’s first stars are believed

to be 30 to 300 times as massive

as our sun and millions of times

as bright. They would have burned

for only a few million years before

dying in tremendous explosions,

or “supernovae.” These explosions

ejected the chemical elements of

the massive stars outward into the

universe, enriching later generations

of stars. The dying stars then

collapsed into black holes or

were destroyed.

Scientists suspect the newborn

black holes gobbled up gas and

stars around them, becoming the

extremely bright objects called

“mini-quasars.” The mini-quasars

may have grown and combined

with other mini-quasars to become

the huge black holes found in the

centers of galaxies. Webb will try to

find these supernovae and mini-

quasars to help astronomers put

theories of early universe formation

to the test.

Hunting for the first galaxies

Galaxies are where the action is.

They’re where most star birth,

life, and death takes place. The

production of heavy elements, the

formation of planets, and, eventually,

the beginning of life also take place

in galaxies.

The Webb telescope is designed to

study the small groups of stars that

make up the early building blocks

of today’s galaxies. Webb will reveal

when galaxies first appeared and

will provide information about their

environment. Webb will analyze

the heavy elements produced by

supernovae. It will examine the

exchange of material between

galaxies and the gas, dust, and

space between galaxies, called the

intergalactic medium. The telescope

will help scientists test the theory

that small galaxies cluster together

and merge to form larger galaxies.

It will investigate the relationship

between the evolution of galaxies

and the development of the huge

black holes at their centers.

The birth of stars and planets

Stars and planets form together

from clouds of gas and dust within

galaxies like our Milky Way. Portions

of these clouds collapse under

Planet orbiting the star Fomalhaut

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origins of planets, including the

mysteries of the earliest objects in

our own solar system.

Seeking living planets

Planets exist outside of our solar

system, orbiting distant stars.

If other planets exist, could life

have taken hold elsewhere in

the universe? Learning about the

formation and evolution of planets

— including our own — will help

us understand whether other stars

could develop life-bearing planets.

Webb will investigate the nature

of Jupiter-like planets in other

solar systems to help astronomers

determine how their formation

might affect the creation of rocky

planets like Earth.

their own gravity into denser and

denser clumps to create the cores of

just-forming stars. A small amount

of dust and gas remains free of

the stars and combines, forming

flattened, pancake-shaped disks

around the young stars. Within a

few million years, this disk material

collects into large bodies and

clumps of debris, forming giant and

rocky planets — perhaps like those

in our own solar system.

Webb will probe deeply into the

dusty disk that surrounds and hides

young stars. The telescope can

explore the structure of this material

to determine the conditions in the

disk at the time of planet formation.

These observations will help unravel

the questions that surround the birth

and early evolution of stars and the

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Extrasolar planet and parent starThis artist’s impression shows a dramatic close-up view of the extrasolar planet XO-1b passing in front of a sun-like star, located 600 light-years from Earth. The Jupiter-sized planet is orbiting dangerously close to its star, completing an orbit every four days.

IMAGE: NASA, ESA, and G. Bacon (STScI)

Scientists believe that the disks

of dust and debris found circling

certain stars may be the beginnings

of new solar systems. Webb will

study these disks around young

stars to look for similarities

and differences between their

composition and the materials in

our own solar system.

Today’s telescopes can find planets

by watching the changes in the

light of a star that occur as a planet

passes in front of it. Webb will

be able to determine the sizes of

the planets and even the chemical

makeup of their atmospheres,

providing a rich survey of extrasolar

planetary systems.

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Jupiter in near-infrared light

Our solar system beginnings

Webb will study the atmospheres of

solar system planets such as Mars.

The telescope also will observe

moons, including Titan, to analyze

their chemical makeup. Webb’s

observations of the giant planets,

such as Jupiter and Saturn, will

give astronomers a better picture of

the planets’ seasonal weather. The

telescope’s infrared vision also will

be useful for studying the surfaces

of planets and moons in the outer

solar system, and those obscured by

cloud layers.

The New Horizons Pluto flyby

provided astronomers with new

information about the dwarf planet

Pluto, located in the outer solar

system. Astronomers plan to use

the Webb telescope for follow-up

observations of Pluto. Webb also

will be able to measure the surface

chemistry of Pluto, its moons, and

many other icy objects that reside in

the Kuiper belt. The Kuiper belt is

a large region of ancient, icy rocks

that are the building blocks of our

solar system’s makeup 4.5 billion

years ago.

The Webb telescope also will closely

examine comets, which are made of

material left over from the formation

of the planets. Scientists can

compare the makeup of comets with

planet- and star-forming dust and

debris to learn how solar system

objects form and evolve. Comets are

also one possible supplier of the

Earth’s water, seeding the planet

with water vapor through millions

of impacts over billions of years.

Webb will help confirm or dismiss

this theory by examining comets’

composition.

Future, unknown science

When scientists sent Hubble into

space, they never expected to find

that the expansion of the universe

was speeding up. Theory said

it should be slowing down. Nor

did they realize they would have

obtained front-seat tickets to watch

a comet crash into Jupiter or see a

Mars global dust storm.

Webb’s true value will be known

only after it reaches its place among

the stars. The greatest science

it reveals may be the questions

no one has thought to ask yet,

the discoveries so unknown, so

unexpected, that they open new

realms of thought, new floods of

questions. Webb’s greatest science

may very well lie in areas that have

yet even to be imagined.

IMAGE: Gemini Observatory/AURA, Chris Go

This image, taken in near-infrared light by the Gemini Observatory, shows two giant red spots brushing past one another in Jupiter’s Southern Hemisphere. In near-infrared light, the red spots appear white rather than the reddish hue seen at visible wavelengths. Both red spots are massive storm systems. The Great Red Spot is the largest hurricane known in the solar system. The smaller storm, known as Red Spot Junior, is another hurricane-like system. Red Spot Junior is roughly half the size of its famous cousin, but its winds blow just as strong.

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