Webb Telescope to make a splash in search for interstellar water

Blue light from a newborn star lights up the reflection
nebula IC 2631. This nebula is part of the Chamaeleon
star-forming region, which Webb will study to learn more
about the formation of water and other cosmic ices. Credit:
European Southern Observatory (ESO)

Water is crucial for life, but how do you make water? Cooking
up some H2O takes more than mixing hydrogen and oxygen. It
requires the special conditions found deep within frigid
molecular clouds, where dust shields against destructive
ultraviolet light and aids chemical reactions. NASA’s James
Webb Space Telescope will peer into these cosmic reservoirs
to gain new insights into the origin and evolution of water
and other key building blocks for habitable planets.

A molecular cloud is an interstellar cloud of dust, gas, and a
variety of molecules ranging from molecular hydrogen (H2) to
complex, carbon-containing organics. Molecular clouds hold most
of the water in the universe, and serve as nurseries for
newborn and their planets.

Within these clouds, on the surfaces of tiny dust grains,
hydrogen atoms link with oxygen to form water. Carbon joins
with hydrogen to make methane. Nitrogen bonds with hydrogen to
create ammonia. All of these molecules stick to the surface of
dust specks, accumulating icy layers over millions of years.
The result is a vast collection of “snowflakes” that are swept
up by infant planets, delivering materials needed for life as
we know it. “If we can understand the chemical complexity of
these ices in the molecular cloud, and how they evolve during
the formation of a star and its planets, then we can assess
whether the of life should
exist in every star system,” said Melissa McClure of the
Universiteit van Amsterdam, the principal investigator on a
research project to investigate cosmic ices.

In order to understand these processes, one of Webb’s
Director’s Discretionary Early Release Science projects will
examine a nearby star-forming region to determine which ices
are present where. “We plan to use a variety of Webb’s
instrument modes and capabilities, not only to investigate this
one region, but also to learn how best to study cosmic ices
with Webb,” said Klaus Pontoppidan of the Space Telescope
Science Institute (STScI), an investigator on McClure’s
project. This project will take advantage of Webb’s
high-resolution spectrographs to get the most sensitive and
precise observations at wavelengths that specifically measure
ices. Webb’s spectrographs, NIRSpec and MIRI, will provide up
to five times better precision that any previous space
telescope at near- and mid-infrared wavelengths.

NASA's Webb Telescope to make a splash in search for interstellar water
In this animation we fly into a protoplanetary disk
surrounding a young star. Within the disk, tiny dust grains
accumulate layers of ice over thousands of years. These
cosmic snowflakes are swept up by forming planets, delivering
key ingredients for life. Credit: NASA/JPL-Caltech/R. Hurt

Infant stars and comet cradles

The team, led by McClure and co-principal investigators Adwin
Boogert (University of Hawaii) and Harold Linnartz
(Universiteit Leiden), plans to target the Chamaeleon Complex,
a star-forming region visible in the southern sky. It’s located
about 500 light-years from Earth and contains several hundred
protostars, the oldest of which are about 1 million years old.
“This region has a bit of everything we’re looking for,” said

The team will use Webb’s sensitive infrared detectors to
observe stars behind the . As light from those faint,
background stars passes through the cloud, ices in the cloud
will absorb some of the light. By observing many background
stars spread across the sky, astronomers can map ices within
the cloud’s entire expanse and locate where different ices
form. They will also target individual protostars within the
cloud itself to learn how ultraviolet light from these nascent
stars promotes the creation of more complex molecules.

Astronomers also will examine the birthplaces of planets,
rotating disks of gas and dust known as protoplanetary disks
that surround newly formed stars. They will be able to measure
the amounts and relative abundances of ices as close as 5
billion miles from the infant star, which is about the orbital
distance of Pluto in our solar system.

“Comets have been described as dusty snowballs. At least some
of the water in Earth’s oceans likely was delivered by the
impacts of comets early in our solar system’s history. We’ll be
looking at the places where comets form around other stars,”
explained Pontoppidan.

This simulated spectrum from the Webb telescope illustrates
the kinds of molecules that may be detected in star-forming
regions like the Eagle Nebula (background). Credit: NASA,
ESA, the Hubble Heritage Team, and M. McClure (Universiteit
van Amsterdam) and A. Boogert (University of Hawaii)

Laboratory experiments

In order to understand Webb’s observations, scientists will
need to conduct experiments on Earth. Webb’s spectrographs will
spread incoming infrared light into a rainbow spectrum.
Different molecules absorb light at certain wavelengths, or
colors, resulting in dark spectral lines. Laboratories can
measure a variety of substances to create a database of
molecular “fingerprints.” When astronomers see those
fingerprints in a spectrum from Webb, they can then identify
the molecule or family of molecules that created the absorption

“Laboratory studies will help address two key questions. The
first is what molecules are present. But just as important,
we’ll look at how the ices got there. How did they form? What
we find with Webb will help inform our models and allow us to
understand the mechanisms for ice formation at very low
temperatures,” explained Karin Öberg of the Harvard-Smithsonian
Center for Astrophysics, an investigator on the project.

“It will take years to fully mine the data that comes out of
Webb,” Öberg added.

The James Webb Space Telescope will be the world’s premier
infrared space observatory of the next decade. Webb will help
humanity solve the mysteries of our solar system, look beyond
to distant worlds around other stars, and probe the mysterious
structures and origins of our universe and our place in it.
Webb is an international project led by NASA with its partners,
ESA (European Space Agency) and CSA (Canadian Space Agency).

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