Why Leave the Observatory? ... The Reason a 12-Trillion-Won 'Gold Mirror' Went to Space [Reading Science]

[Asia Economy Reporter Kim Bong-su] The James Webb Space Telescope (Web Telescope), the greatest celestial observation instrument ever developed by humanity, finally reached its target orbit at the Lagrange Point 2 (L2) at 2 p.m. on the 25th (Eastern Time, USA). NASA, the Canadian Space Agency (CSA), and the European Space Agency (ESA) invested an astronomical budget of 12 trillion won, 15 years of production time, and over 10,000 personnel. Equipped with cutting-edge technology, it boasts more than 100 times the performance of the existing Hubble Space Telescope and is expected to "rewrite the space textbook" by unveiling the secrets of the universe's birth, searching for exoplanets and extraterrestrial life. Let's take a closer look at what exactly the James Webb Space Telescope is for.

◆ 'An Observatory Launched into Space'

Launching a space telescope requires cutting-edge technology and enormous costs for production, launch, and operation. Initially, the Web Telescope was planned with a budget of about 1 billion dollars, but due to delays in technology development and other twists and turns, the production and launch costs surged to 10 billion dollars (approximately 12 trillion won). The launch cost of the Ariane 5 rocket used as the launch vehicle alone exceeds 10,000 dollars per kilogram. Considering its weight of 6.21 tons, this cost amounted to 70 to 80 billion won. Moreover, there are countless observatories on Earth equipped with high-performance cameras. So why bother launching a space telescope?

There are two main reasons. First, celestial bodies that cannot be observed from the ground can be seen from space. The light emitted by stars is classified by wavelength from short to long as gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, and radio waves. The shorter the wavelength, the higher the energy; the longer the wavelength, the lower the energy. Among these, only visible light and radio waves reach the Earth's surface, while ultraviolet rays, infrared rays, gamma rays, and X-rays are blocked by clouds (water molecules), water vapor, or carbon dioxide in the Earth's atmosphere. Therefore, ground telescopes are limited to optical telescopes for visible light and radio telescopes. Even visible light images are blurred by atmospheric turbulence, which is why stars appear to twinkle. In space, without an atmosphere, clear observations are possible without such interference. Additionally, unlike on Earth, observations can be made 24 hours a day regardless of weather conditions.

◆ Specifications, Performance, and Mission

The Web Telescope is the most recently completed space telescope using the latest technology. It consists of a primary mirror, secondary mirror, and a sunshield. The primary mirror is hexagonal with a diameter of 6.5 meters and an area of 25 square meters, composed of 18 hexagonal mirror segments each 1.3 meters in diameter, forming a honeycomb-shaped ultra-lightweight structure. While the Hubble Space Telescope (hereafter Hubble) used metal-coated glass, which was heavy, the Web Telescope uses beryllium for its mirror plates, which is six times stronger than steel but lightweight and very stable. The surface of the beryllium is coated with a 100 nm thin layer of gold, which reflects 99% of infrared rays. To observe the infrared rays from stars smoothly, sunlight and heat must be blocked. For this purpose, a five-layer sunshield, which unfolds like a parasol to the size of a tennis court, is also installed.

As a cutting-edge space telescope, it is equipped with ultra-low power computers, 128 fine-tuning shutters, cryogenic coolers, and four types of advanced optical instruments. First, the Near-Infrared Camera (NIRCam) performs imaging and spectroscopic observations in the near-infrared wavelength range of 0.6 to 5.0 μm. It is equipped with a coronagraph capable of observing faint celestial bodies such as exoplanets and dust disks. It also has the Near-Infrared Spectrograph (NIRSpec) for multipurpose spectroscopic research, the Mid-Infrared Instrument (MIRI) with a coronagraph, and the Near-Infrared Imager and Slitless Spectrograph (NIRISS) for low-resolution, wide-field spectroscopic research. Thanks to these advanced instruments, the Web Telescope boasts 100 times the resolution and sensitivity of the existing Hubble Space Telescope.

After its launch on the 25th of last month, the Web Telescope attracted attention by transforming like the robots in the movie 'Transformers' during its approximately 150 km journey over a month. NASA designed the major components to fold like origami to fit the Web Telescope into the payload bay of the Ariane 5 rocket, which is only 5 meters in diameter, so about 10 days after launch, the telescope was unfolded and secured.

The Web Telescope will begin its full-scale mission of observation and data transmission from the end of June. Over the next five months, the tilt of the 18 mirrors must be finely adjusted and integrated. Additionally, the internal temperature must be lowered to minus 233 degrees Celsius to optimize the operating conditions of the internal equipment.

◆ Differences Between Hubble and the Web Telescope

Launched into space in 1990, Hubble has a 2.4-meter diameter primary mirror, which is much smaller than the 6.5-meter primary mirror of the Web Telescope, resulting in significantly inferior performance in resolution and sensitivity. Hubble can observe star light up to about 12.5 billion light-years away in visible light only. This means that stars or galaxies shrouded in distant dust clouds cannot be observed by Hubble because visible light cannot penetrate the dust. However, the Web Telescope can observe these because infrared rays, which have longer wavelengths than red light, can penetrate dust layers. Another major difference is that while Hubble orbits Earth at an altitude of 600 km, the Web Telescope orbits the Sun at the L2 point, 1.5 million km away. Hubble is affected by Earth, limiting its clarity and observation distance, but the Web Telescope is free from such constraints. Also, the Lagrange Point 2 is where the gravitational and centrifugal forces of the Sun and Earth balance, requiring no additional propulsion, which enhances sustainability. However, the Web Telescope is too far away for direct repairs if it malfunctions. NASA plans to send repair missions only when super-heavy launch vehicles like SpaceX's Starship or its own SLS are completed. Therefore, the system is designed for remote operation and repair via the Deep Space Network from Earth, and it was built with countless repeated tests and durable materials, systems, and components.

◆ Why Is It Called a 'Time Machine'?

The main mission of the Web Telescope is to observe galaxies in the early universe and explore exoplanets surrounded by distant dust clouds. It also aims to observe relatively distant planets in the solar system such as Jupiter and Saturn in greater detail and search for the possibility of extraterrestrial life. It is called a 'time machine' because of its connection to the 'secrets' of the universe's birth. The Web Telescope's maximum observation capability allows it to capture infrared rays from stars about 13.5 billion light-years away, meaning it observes light from galaxies and stars that started traveling 13.5 billion years ago. Since the age of the universe is estimated to be about 13.8 billion years, these stars and galaxies from 13.5 billion years ago represent the 'early universe.' In other words, the Web Telescope enables the study of the formation and evolution of stars and galaxies from the early universe, hence the nickname 'time machine.'

It will also accelerate the confirmation of exoplanets by observing brightness variations of distant stars. Currently, about 3,000 exoplanets have been discovered. The Web Telescope is expected to analyze the composition of planets by detecting infrared wavelengths emitted from stars, playing a role in finding planets that may harbor extraterrestrial life. NASA stated, "(The launch of the Web Telescope) is a scientific Apollo moment (a giant leap) that will fundamentally change our understanding of the universe. It can observe everything from planets, star nebulae, galaxies, and beyond. It will reveal the secrets of the universe and exoplanets, search for life in the solar system, and detect faint signals from the earliest galaxies. It will uncover everything we do not know, from star formation to black holes, and beyond."

Dr. Kim Young-soo of the Korea Astronomy and Space Science Institute explained, "The reason major countries are investing 12 trillion won to launch the Web Telescope and engage in space observation is not only scientific curiosity about the mysteries of the universe and the search for life. It is also to prepare for future space exploration, to respond to potential threats from space, and to utilize spin-off technologies derived from new materials and new technology development in industries such as medicine, defense, and more."