It's a moment that has been decades in the making. The launch of the James
Webb Space Telescope, NASA's premier observatory of the next decade, is
scheduled for December 18 from French Guiana.
The telescope has endured years of delays, including a combination of
factors brought on by the pandemic and technical challenges. But the world's
most powerful complex space observatory will answer questions about our
solar system, study exoplanets in new ways and look deeper into the universe
than we've ever been able to.
Webb will peer into the very atmospheres of exoplanets, some of which are
potentially habitable, and could uncover clues in the ongoing search for
life outside of Earth.
The telescope comes equipped with a mirror that can extend 21 feet and 4
inches (6.5 meters) -- a massive length that will allow the mirror to
collect more light from the objects it observes once the telescope is in
space. The more light the mirror can collect, the more details the telescope
can observe.
The mirror includes 18 hexagonal gold-coated segments, each 4.3 feet (1.32
meters) in diameter.
It's the largest mirror NASA has ever built, the agency said, but its size
created a unique problem. The mirror was so large that it couldn't fit
inside a rocket. So they designed the telescope as a series of moving parts
that can fold origami-style and fit inside a 16-foot (5-meter) space for
launch.
Each space telescope builds on the knowledge gained from the previous one.
In the case of Webb, its mirror is nearly 60 times larger than previous
space telescopes, like the retired Spitzer Space Telescope. The observatory
also improves on the sensitivity and resolution of the Hubble Space
Telescope.
Webb will act as an infrared detective, detecting light that is invisible to
use and revealing otherwise hidden regions of space, according to NASA.
The concept for the telescope was first imagined as a successor to Hubble at
a workshop in 1989 and construction on Webb first began in 2004. Since then,
thousands of scientists, technicians and engineers from 14 countries have
spent 40 million hours building the telescope.
Now, Webb is ready to help us understand the origins of the universe and
begin to answer key questions about our existence, such as where we came
from and if we're alone in the cosmos.
What Webb will see
The Webb telescope will look at every phase of cosmic history, including the
first glows after the big bang that created our universe and the formation
of the galaxies, stars and planets that fill it today. Its capabilities will
enable the observatory to answer questions about our own solar system and
investigate faint signals from the first galaxies formed 13.5 billion years
ago.
The science goals for Webb are ambitious, and scientists around the world
will use their allotted time using the telescope to observe and analyze a
broad spectrum of planets, black holes, galaxies, stars and the structure of
the universe itself.
A key focus is planet formation and evolution, both in our solar system as
well as the large population of planets outside of it. Of particular
interest are planets located within the habitable zone of stars, an orbital
region where a planet is the right temperature to support liquid water on
its surface -- which suggests it could potentially support life as we know
it.
Spitzer, as well as NASA's ongoing planet-hunting Transiting Exoplanet
Survey Satellite (TESS) mission, have helped scientists establish targets
for follow-up by Webb, including some of Spitzer's "greatest hits." Webb
will be able to characterize exoplanets, going beyond Spitzer's capabilities
of measuring how big a planet is and seeing the intricate details of how
they look.
For example, in February 2017 astronomers announced their discovery of seven
Earth-size planets orbiting a star 40 light-years from Earth. With Spitzer's
help, the seven exoplanets were all found in tight formation around an
ultracool dwarf star called TRAPPIST-1. The planets all bear the TRAPPIST
name -- which the researchers borrowed from their favorite beer.
One of the planned targets for Webb is TRAPPIST-1e, which could support
liquid water on its surface. Finding water could suggest the potential for
life as well. Another target for early in the mission is WASP-18b, a blazing
"hot Jupiter" with an atmosphere, according to NASA.
Webb is also well equipped to shed light on the mysteries of planet
formation. Building off Spitzer's work studying brown dwarfs -- objects that
are too large to be planets but too small to be stars -- Webb can take a
closer look at their cloud properties.
The telescope will take a closer look at a selection of exoplanets to peer
inside their atmospheres, if they have them, and help answer questions about
how the planets formed and evolved. Its spectroscopic data can tell
scientists if methane, carbon dioxide or carbon monoxide is in the
atmosphere. The gases within these alien atmospheres could reveal the very
building blocks of life.
Other objects of interest for the intiial science campaign include observing
the supermassive black hole at the center of the Milky Way, actively forming
planetary systems, bright quasars at the center of galaxies and leftovers
from the formation of our solar system known as Kuiper Belt Objects
including Pluto and its moon Charon.
What it can do
With all of its superlatives, engineering Webb was an extraordinary
challenge.
The observatory is comprised of three main elements.
One is the Integrated Science Instrument Module, which holds Webb's suite of
four instruments. These instruments will mainly be used for capturing images
or spectroscopy -- breaking down light into different wavelengths to
determine physical and chemical components.
The Optical Telescope Element, the main eye of the observatory, includes the
mirrors and backplane, or spine, that supports the mirrors. And then there's
the Spacecraft Element, which includes the spacecraft bus and sunshield.
The bus includes the six main subsystems needed to operate the spacecraft,
including propulsion, electrical power, communication, data and thermal
controls.
The five-layer sunshield unfurls to reach the size of a tennis court and it
will protect Webb's giant mirror and instruments from the sun's heat because
they need to be kept at a very frigid negative 370 degrees Fahrenheit
(negative 188 degrees Celsius) to operate.
The advances used to design and build the telescope even have benefits for
those of us on Earth. A technique developed to quickly and accurately
measure the mirrors so they could be polished has been adapted for surgeons
performing LASIK eye surgery because it creates high-definition maps of
patients' eyes.
When to expect the first images
If you've heard of the "seven minutes of terror" when the Perseverance rover
landed on Mars, the Webb team has a much longer and more grueling waiting
period. The agency has referred to it as "29 days on the edge."
After launching from French Guiana, the observatory will travel for about a
month until it reaches an orbit about 1 million miles (1.6 million
kilometers) away from Earth. During those 29 days, Webb will unfold its
mirrors and unfurl the sunshield. This process involves thousands of parts
that must work perfectly in the right sequence.
Fortunately, each step can be controlled from the ground in case there are
issues.
And then it will go through a period of commissioning in space that lasts
for six months, which involves cooling down the instruments, alignment and
calibration. All of the instruments will go through a checkout process to
see how they're functioning.
Then, it will begin to collect data and its first images later in 2022.
Thousands of scientists have been waiting for years to see what Webb can
show us.
"The initial year of Webb's observations will provide the first opportunity
for a diverse range of scientists around the world to observe particular
targets with NASA's next great space observatory," said Thomas Zurbuchen,
associate administrator for the Science Mission Directorate at NASA, in a
statement. "The amazing science that will be shared with the global
community will be audacious and profound."