The James Webb Space Telescope is our next great observatory in space.
Forged from the fires of curiosity and fueled by 25 years of discovery from the Hubble Space Telescope,
new questions have emerged that require a new set of eyes on the cosmos.
Astronomers and cosmologists around the world have chosen JWST as the flagship to begin
a new chapter of discovery.
With Hubble's discoveries as a starting point, JWST was designed peer farther and
capture objects fainter than Hubble could ever hope to, and it will address four main
scientific realms of interest for astronomers and cosmologists.
JWST will peer deep into the history of our cosmos into a time known as the end of the Dark Ages
This is a period in our universe when the first stars and galaxies were formed.
According to theory as well as observations from the Wilkinson Microwave Anisotropy Probe
(WMAP), the universe has expanded by a factor of 20 since the Big Bang during this period,
the mean density was 8000 times greater than it is now, and the age of the cosmos was only
about 180 million years.
The first stars to emerge from this time were 30 to 1000 times as massive as the Sun and
millions of times as bright and burned for only a few million years before meeting a
violent end.
Each one would produce either a super luminous pair-instability supernova or collapse directly
to a black hole.
These supernovae would come to enrich the surrounding gas with the chemical elements
produced in their interiors, and future generations of stars would all contain these heavier elements,
referred to by astronomers as 'metals'.
The black holes produced from these violent deaths would start to consume gas and other
stars to become mini-quasars, growing and merging to become the supermassive black holes
now found at the centers of nearly all galaxies.
Galaxies are the visible building blocks of the universe.
Theories developed through observation give us a preferred picture of the assembly of
galaxies.
It seems that small objects formed first, and then were drawn together by gravity to
form larger ones.
This process is still occurring today, as our Milky Way merges with some of its dwarf
companions, and as the enormous Great Andromeda Galaxy heads toward the Milky Way for a future
collision billions of years hence.
With Hubble, galaxies have been observed back to times about 400 million years after the
Big Bang.
While most of these early galaxies are smaller and more irregular than those of today, some
early galaxies are very similar to those seen nearby and astronomers want to learn why.
Astronomers do not really know how galaxies are formed, what controls their shapes, what
makes them form stars, or how the chemical elements are generated and redistributed through
the galaxies, nor whether the central black holes exert great influence over the galaxies.
JWST will be able to observe galaxies back to their earliest precursors so that we can
understand their growth and their morphological and metallicity evolution.
The James Webb Space Telescope will provide imaging and spectroscopy over bright range
of infrared wavelengths to uncover many of these mysteries of the very first galaxies
ever to form in the universe.
The study of stars is as old as the field of astronomy but, only in recent times have
we begun to understand them from detailed observations and computer simulations.
A hundred years ago we didn't know that they are powered by nuclear fusion, and 50 years
ago we didn't know that stars are continually being formed.
We still do not know the details of how stars are formed from clouds of gas and dust, or
why most stars form in groups, or how planets form with them.
We also do not know the details of how they evolve and liberate the so-called "metals"
back into space for recycling into new generations of stars and planets.
In many cases these old stars have major effects on the formation of new ones.
Astronomers have learned that most stars are formed in multiple star systems and that many
have planets.
However, there is little agreement about how this occurs, and the discovery of large numbers
of massive planets in very close orbits around their stars was very surprising.
We also know that planets are common around late-type stars - these are stars cooler and
less massive than the Sun - and that debris disks might signal their presence.
Understanding the origin of the Earth and its ability to support life has been a burning
question that impacts all of humanity and is central to the JWST science program.
Astronomers will use JWST to understand the formation of small objects and how they combine
to form large ones, learning how they reach their present orbits, how the large planets
affect the others in systems like ours, and about the chemical and physical history of
the small and large objects that formed the Earth and delivered the necessary chemical
precursors for life.
One of the main uses of the James Webb Space Telescope will be to study the characteristics
of exoplanets, to search for the building blocks of life elsewhere in the universe.
To do this, it will study the atmospheres of planets around distant stars as the host
star's light travels through any atmosphere the exoplanet might have.
Using spectra to determine the composition, astronomers using JWST will be able to determine
if there is any water as well as any telltale signs of life, like increased methane concentrations.
In addition to studying planets outside our solar system, scientists want to learn more
about our own home.
JWST complements NASA's other solar system missions, including those observatories on
the ground, orbiting Earth, and in deep space.
Data in different wavelengths and from different sources can help us build a broader, fuller
picture of the objects in our solar system especially with the help of JWST's unprecedented
improvements in sensitivity and resolution.
JWST will observe Mars and the giant planets, minor planets like Pluto and Eris - and even
the small bodies in our solar system: asteroids, comets, and Kuiper Belt Objects.
The infrared capabilities of JWST will help us understand cool objects and dust in the
outer Solar System.
These outer regions still provide a glimpse of conditions in the early Solar System, and
are directly comparable to cool objects and dust observed around other stars.
From its inception, the James Webb Space Telescope has been designed to answer some of the most
burning questions astronomers have had for centuries: what were the first stars and galaxies
like?
How did they form?
How exactly do stars and planets come about?; what is our solar system really like?; and
what about the billions of planets orbiting other stars: are they habitable for us?; What
are the possibilities for life elsewhere?; Where do we fit in?
When JWST launches from the titanic Ariane V on the French Guyana coast in October 2018,
capabilities become available in our quest for understanding the cosmos that we've
never before had: a set of eyes will be open for the first time, heralding in a bright,
new era in humanity's attempt to understand itself.
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