The James Webb Telescope

The James Webb Space Telescope is finally here!

Well, it’s actually 1.5 million km away from us

NASA engineer Ernie Wright looks on as the James Webb Space Telescope's primary mirror segments are prepped to begin final cryogenic testing at NASA's Marshall Space Flight Centre.

Astronomy was given the best Christmas present this year: the successful launch of the James Webb Space Telescope (JWST). From the birth of such a concept in 1996, the project suffered multiple technical problems and delays, with its budget soaring from $500 million to a whopping $10 billion. Criticisms aside, there is no doubt its highly-anticipated launch on 25th December came as a relief to those at NASA, ESA and the Canadian Space Agency who collaborated on the project. In 1996, the Hubble Space Telescope, predecessor of JWST, viewed a seemingly empty region of the sky. Upon closer inspection, the Hubble Deep Field image showed the opposite. Turns out, that region housed 3000 galaxies, some of which were the oldest ever observed. The astronomers subsequently worked on building the Next Generation Space Telescope to probe this further, which later evolved into the JWST. The idea was revolutionary, but was met with several obstacles. Technical problems with the sun shield and thrusters meant its planned launch in 2018 was pushed back. When COVID-19 hit, pandemic protocols delayed the launch date even further, from March 2021 to December 25th, the day JWST finally took its leap into the cosmos. Launched on the ESA’s Ariane 5 rocket from French Guiana, JWST reached the moon’s orbit in 3 days. On 4th January, JWST unfolded and tensioned its sunshield, a meticulous manoeuvre comprising a total of over 140 release mechanisms. Once this was deployed successfully between the telescope and the Sun, Earth and moon, its secondary and primary mirrors were unfolded. 27 days after its launch, JWST then reached the second Lagrange point (L2), 1.5 million km from Earth (in the direction opposite to the Sun). L2 is one of the five Lagrange points established in the 18th century. It is the point where the gravitational forces of the Earth and the Sun are equal, meaning JWST would orbit steadily around the Sun along with the Earth, only needing rocket thrust every three weeks to keep it in orbit. At L2, it would not be precisely stationary; instead, it would orbit around L2 in a “halo orbit” . The instruments were then turned on and astronomers began calibrating them, a key step to ensure images captured by the observatory were perfectly aligned. JWST took its first picture of its mirrors (a “ mirror selfie” , some may even call it), and astronomers have proceeded to align the 18 hexagonal mirrors. After all of this, JWST will be ready to capture images of everything from exoplanets and stars, to the most distant galaxies. (Update: as of April 2022, JWST has sent back an image of a star - our highest resolution yet! The alignment process is nearly completed, and its instruments and mirrors are nearly fullycooled.) The advanced design of the JWST caters to the primary function of the observatory: to look at infrared radiation. As our universe continues to expand, light travelling from distant galaxies to us stretches in wavelength towards the infrared side of the electromagnetic spectrum, resulting in a phenomenon termed “ red shift” .

Josef Aschbacher and Thomas Zurbuchen celebrate after hearing confirmation that the James Webb Space Telescope successfully separated from the Ariane 5 rocket.

About 13.6 billion years ago, the first stars and galaxies were born, and light emitted from them has now redshifted. Hope therefore remains high that the JWST will be our modern way of looking back in time, that peering into the infrared spectrum will yield interesting findings about the young universe. Because infrared radiation is given out by warm objects, heat must be reflected from the observatory to ensure clear images are captured. A sunshield made of five layers of Kapton, a lightweight thermal material, is designed to cater to this need. Spanning the width of a tennis court, it keeps the side facing away from the Sun at -233°C, while the other side is exposed to 85°C. At L2, the large distance from the Sun further ensures scientific instruments aboard are kept sufficiently cool. Furthermore, the JWST also has 18 hexagonal mirrors arranged in a honeycomb pattern that are gold-plated to reflect and focus infrared light onto the ISIM (Integrated Science Instrument module), which subsequently produces images. All of this means the JWST, when compared to the Hubble Space Telescope, is capable of viewing objects that are 10-100 times fainter, 10 times more precisely! With 300 observing programmes planned, the mission of the JWST falls under 4 main pillars. They aim to elucidate how the first stars and galaxies were formed 100-250 million years after the Big Bang, which occurred 13.6 billion years ago. Another long-standing mystery in astronomy is dark matter content. Our universe is made up of five times as much dark matter as “ normal” (baryonic) matter, but scientists cannot measure this directly as dark matter does not interact with baryonic matter. Equipped with gravitational lensing techniques, astronomers at JWST will indirectly investigate dark matter content through studying faraway galaxies, and also gain insight into the formation and evolution of

Lagrange Points 1-5 of the Sun-Earth system

18th century mathematician Joseph-Louis Lagrange found 5 solutions to the “three-body problem” , which asked if there were any stable configurations where three bodies could orbit each other while staying in the same position relative to each other. These 5 solutions then became the 5 Lagrange points (see diagram), locations where the gravitational forces of two large masses and the centripetal force needed for a small mass to move between them are equal.

galaxies over time. JWST will also investigate the formation of stars and planetary systems whilst studying exoplanets in search of signs of alien life. TRAPPIST-1 is a star of particular interest as 3 of the 7 planets orbiting it are in the habitable zone, and one of them may even contain liquid water! The long-awaited launch of the JWST was undoubtedly a significant event in space exploration. As we follow the news of JWST making its ambitious way through the cosmos, who knows what kind of new information about our universe will be discovered! Vanessa Yip

This image is JWST's first image of a star which is called 2MASS J17554042+6551277, and uses a red filter to optimize visual contrast. The background shows other stars and galaxies. It is the highest resolution infrared image ever taken from space. Credit: (NASA/STScI)