JWST or Webb is NASA, ESA, and the Canadian Space Agency (CSA) telescope, initially known as Next Generation Space Telescope (NGST), was later remade to James Webb Space Telescope (JWST) in honor of NASA's second administrator. James Webb led NASA during the Apollo program.

The agencies have been collaborating since 1996 to design and build a successor for Hubble that will cause a more significant impact on astrophysics. Webb's launch is planned for this year (2021), and it is required to operate a minimum of five years; however, it was planned for ten years. JWST will help us understand the Universe and our origins by observing infrared light from the youngest galaxies and possibly the first stars.    

A Bit of Astrophysics

After the Big Bang, "Our whole Universe was in a hot, dense state. Then nearly fourteen billion years ago expansion started, wait."* The Universe, after the Big Bang, was a hot soup of particles. When it started cooling, protons and neutrons combed into ionized atoms of hydrogen and some helium. These ionized atoms attracted electrons, converting them into neutral atoms, which allowed light to travel freely for the first time. However, it would still take a few hundred million years, the exact moment is unknown, for the early sources of light start to form, ending the cosmic dark ages. What these first light looked like is also unknown, and Webb will help understand. "It's math, science, history, unraveling the mysteries. That all started with the big bang!"*   

Galaxies were more active in the early Universe, colliding and forming stars more often. They glowed very brightly in the ultraviolet and visible parts of the light. However, the light from the first stars and galaxies traveled through space for nearly 13.6 billion years until they reach our telescopes. In other words, we see these stars and galaxies as they were 13.6 billion years ago. Although, their color or wavelength has shifted toward red due to the redshift phenomenon. With the expansion of the Universe, the space among objects also stretches, and bodies move away from each other. It is like baking a fruitcake; when the dough rises, it is like the fruits moved apart from each other. Any light in the space among objects will also stretch, and the wavelength will shift towards longer wavelengths (red). That can make distant objects less or not visible at all because the light reaches us as infrared light part of the electromagnetic spectrum, which is not visible by human eyes. Webb's powerful near- and mid-infrared instruments will allow us to study these early galaxies and their evolution, addressing many of the outstanding issues in astronomy.

Stars, including the Sun, change during their lives, which can last billions of years. They can shroud in dense clouds of dust and gas that visible light cannot penetrate. Webb's infrared instruments will penetrate cosmic dust clouds and gas, allowing the study of colder or very distant bodies, unseen stages of stars' life cycles, and the elements and processes that fueled galaxies' formation and activity. Learning about the stars' life cycle can help us understand everything around us, including the elements that make our bodies.

Webb will allow scientists to investigate the central supermassive black holes and dark matter and study planets' properties around other stars, including traces of water in their atmosphere. A spectrum shows how bright an object is at different wavelengths (or colors), giving detailed information about the object. It will allow scientists to determine if distant planets could be habitable if their spectra show lines associated with specific molecules like water, carbon dioxide, methane, and oxygen in their atmospheres. The telescope may even detect signs of alien life, known as biosignatures.  

Webb’s Scientific goals

JWST will be a general-purpose observatory with astronomical instruments to address many prominent galactic and extragalactic astronomy questions. The science goals guiding the design of JWST can be grouped into four themes:

• End of the Dark Ages - First Light and Reionization: It will identify and analyze the first luminous objects after the Big Bang (proto-galaxies, supernovae, and black holes) and study when and how reionization occurred.    

• Assembly of Galaxies: It will examine how the first galaxies formed and evolved until now, the formation and redistribution of heavy elements, and the merging of proto-galaxies. It will help understand what gives galaxies shapes and what happens when galaxies collide or join. It will look at the role of black holes in galaxy evolution and the history of star formation.   

• The Birth of Stars and Protoplanetary Systems (young and dusty solar systems): It will examine the birth and early development of stars, the formation of planets and planetary systems, studying how stars form in dust clouds and how chemical elements are produced and recirculated. With Webb's ability to see in the infrared, astronomers can study "protoplanetary disks" as they are forming. It wasn't possible before because the dust blocks visible light.   

• Planetary Systems and Origins of Life: It will study planetary systems' (including our own) physical and chemical properties and investigate the potential for life elsewhere in the Universe.   

JWST Technical Aspects

The JWST observatory includes three main elements, the Integrated Science Instrument Module (ISIM), the Optical Telescope Element (OTE), and the Spacecraft Element, which consists of the spacecraft bus and the sun-shield. Therefore, the JWST observatory consists of a passively cooled, 6.5-m aperture telescope, optimized for diffraction-limited performance in the near-infrared (2 - 5 μm) region, with extensions to either side into the visible (0.6 - 2 μm) and mid-infrared (5 - 28 μm). JWST's wavelength range covered by the scientific instruments will be from about 0.6 μm to 28 μm (visible to the mid-infrared light), compared to Hubble's 0.1 μm - 2.5 μm (ultraviolet to the near-infrared). The total observatory mass will be 6500 kilograms.   

JWST is enormous, and its primary mirror has an area seven times larger than that of Hubble, making it much more sensitive. It combines excellent image quality, a large field of view, and a low background light level with a highly stable environment. The telescope and its instruments have a cryocooler for cooling to avoid infrared radiation's emission and make precise infrared observations without interfering with signals from observed astronomical objects.   

The heating issue also plays a role in the orbit decision. The sunlight reflected from the Earth's clouds and oceans creates enough heat to disturb observations. JWST will be placed in the Sun-Earth L2 halo orbit, and contrary to Hubble, it won't be serviceable after launch. It also makes operation and pointing/stability requirements more straightforward.  

In our next post, we are going to talk more about Webb's innovative instruments.

Follow us on Linkedin, Twitter, or Facebook to get our updates, including the second part of this post.

This article was written by Juliane Verissímo - Marketing Department of VisionSpace.

*Music theme of The Big Bang Theory Tv show by Barenaked Ladies