by Jolene Creighton August 1, 2016 Space
In Brief
The James Webb Space Telescope (JWST) is set to replace the Hubble Space Telescope. The JWST is set to be 100 times more powerful.

The James Webb Space Telescope is designed to be the successor of the Hubble Space Telescope and the Spitzer Space Telescope. The James Webb Space Telescope (sometimes called JWST) will be a large infrared telescope with a 6.5-meter primary mirror (making it about 5 or 6 times larger than Hubble in area).

The significance of this cannot be overstated, as Hubble is arguably one of mankind’s greatest inventions, and the James Webb is set to be 100 times more powerful.

Image Credit: NASA
Image Credit: NASA

Ultimately, this telescope will pick up where Hubble has left off, which is with the Hubble Ultra and extreme deep field images. Besides the Planck and WMAP satellite images (which gave us the Cosmic Microwave Background Radiation photos), these are the oldest images of light we have collected, and we see distant galaxies far back in the picture…galaxies that aren’t quite brought into focus.

Sadly, these galaxies are just about leaving the visible light spectrum, soon to be red-shifted into the infrared, due to the expansion of the universe.

Fortunately, the James Webb’s instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range. The instruments will be sensitive to light from 0.6 to 28 micrometers in wavelength. Its advanced scientific instruments are poised to tackle four crucial themes: The First Light and Era of Reionization, The Assembling of Galaxies, The Birth of Stars and Protoplanetary Systems, and Planetary Systems and the Origins of Life.

This NASA graphic shows how astronomers hope to see even farther with the future James Webb Space Telescope. Image credit: NASA
This NASA graphic shows how astronomers hope to see even farther with the future James Webb Space Telescope. Image credit: NASA

The First Light

Our best understanding predicts that the first stars were 30 to 300 times (maybe even more) massive as our Sun and millions of times brighter, burning for only a few million years before exploding as supernovae.

The high energy ultraviolet light from these first stars was capable of splitting hydrogen atoms back into electrons and protons (or ionizing them). Observations of the spectra of distant quasars tell us that this occurred when the Universe was almost a billion years old.  This is known as the Epoch of Reionization. The process here, in which much of the neutral hydrogen atoms gets destroyed by the increasing radiation, gives us an opportunity to study the first stars indirectly.

We want to know this because we do not know exactly when this period happened, and the first stars greatly influenced the formation of later objects such as galaxies. The first sources of light act as seeds for the later formation of larger objects.

Also, the first stars may have collapsed into black holes. As these black holes fed on matter, they would form mini-quasars. These, in turn, would grow and merge to form what would be the supermassive black holes found at the center of ALL galaxies.

The Assembly of Galaxies

Astronomers know that the first galaxies formed roughly 1 billion years into the universe’s lifetime. Most of these galaxies were small and irregular, but some draw parallels to nearby galaxies seen today.

Credit: Space-Time and Expansion of the Universe
Credit: Space-Time and Expansion of the Universe

Despite the vast wealth of data already collected, many questions still linger and deserve better answers. Scientists do not really know how galaxies are formed and what gives them their shapes. Scientists do not know how the chemical elements are distributed through the galaxies themselves, and the details of how the central black holes in galaxies influence their host galaxies.

Scientists are also still searching for answers on what happens when small and large galaxies collide and join together – answers that hopefully fare better than their current computer models.

By analyzing the earliest galaxies and comparing them to recent ones, the full evolution and growth can now be fully traceable. Observations using spectroscopy of hundreds or thousands of galaxies will help researchers understand how elements heavier than hydrogen were formed and built up as galaxy formation proceeded through the ages.

The Birth of Stars and Protoplanetary Systems

Thanks to the Kepler Space Telescope, we know that a large number of stars have gas giant planets that orbit them. The number of confirmed planets and candidate planets is now in the thousands. With all the unusual planetary systems, many questions now vex the minds of astronomers.

Scientists realize that to get a better understanding of how planets accreted, they need to have more observations of planets around young stars, and more observations of leftover debris around the stars, which can coalesce together and form planets.

The Formation of Stars

This is where infrared comes in. It is the technology that can pierce the dusty, dense veils of cloud cores where star formation begins. At visible light, these are opaque, not being able to see through it. The James Webb Space Telescope’s advanced imaging and spectroscopy capabilities will permit us to observe stars as they are forming in their dusty cocoons. It will also be able to image disks around stars and study organic molecules that are conducive for life to develop and emerge.

To trace the origins of the Earth and life in the Universe, scientists need to study planet formation and evolution, including the material around stars where planets form. A key issue is to understand how the building blocks of planets are assembled. Scientists do not know if all planets in a planetary system form in place, or travel inwards after forming in the outer reaches of the system.

The First Planets and the Origin of Life

The icy and dusty debris in our outer solar system are remnants of when our system was very young. The JWST will obtain infrared images of giant planets and planetary systems and chart their ages and masses by measuring their spectra. Webb will also be able to measure spectra of the disks around other stars to determine the constituents of such disks that give rise to planetary systems. Studying these areas in detail may give clues how life emerged here on Earth.

The project is working towards a 2018 launch date and is set to revolutionize our understanding on the cosmos.