The telescope will orbit the sun, while simultaneously making small circles around the so-called Lagrange point 2 (L2) - a point on the sun-Earth axis constantly hidden from the sun by the planet. That's more than four times farther than the moon. "And to get really cold, you need to get away from Earth."Īnd the James Webb Space Telescope will be far away from Earth indeed, about 1 million miles (1.5 million km) away. "If you want a really sensitive infrared telescope, it needs to be really cold," McCaughrean said. As a result, its infrared detectors are quite dazzled by the telescope's own warmth and it simply cannot see those faint and distant galaxies. On top of being regularly blasted by direct sunlight, Hubble also absorbs Earth's heat. Hubble orbits Earth at the altitude of 340 miles (545 kilometers). But still, infrared astronomy was an obvious afterthought for Hubble, and the telescope clearly wasn't optimized to feel the warmth of the most distant universe. The Hubble Space Telescope, although originally designed to detect only the visible light of the universe (that in wavelengths that the human eye can process), was in 1997 equipped with then cutting-edge infrared detectors during the second servicing mission these sensors were later upgraded when new technology became available. The scientists and engineers behind JWST needed to tackle a range of technical obstacles to make this hoped-for detection possible. Since the stars and galaxies that JWST was designed to study are so far away, the incoming signals are also extremely faint. Infrared radiation is essentially heat, and can be detected with special sensors that are different from those detecting visible light. That's the same effect that distorts the frequency of a siren of a passing ambulance car. This strange effect, known as the red shift in astronomical jargon, is a result of the expansion of the universe and the ensuing Doppler effect. The James Webb Space Telescope, sometimes fondly referred to by astronomers as the 'first light machine,' was built to see the first stars and galaxies that emerged from dust and gas of the early universe, only a few millions of years after the Big Bang.īecause these stars and galaxies are so far away, the visible light they emitted when the universe was only a few hundred millions of years old has shifted into the near infrared and infrared part of the electromagnetic spectrum. (Image credit: ESA/NASA/STSCI) The first light machine The new telescope will peer deeper into the most ancient universe. The science it is meant to deliver, the depths of space it is intended to glimpse, simply cannot be accomplished with a spacecraft that astronauts can visit (at least not with currently available spaceships).Ī comparison of a Hubble Space Telescope image and a simulated James Webb Space Telescope image. The fact is that serviceability was never an option for Webb. Because we've spent two decades building and testing every single piece a million ways to do everything to make sure it doesn't have problems."īut why does Webb have to be so complex? Wouldn't a simpler mission work just as well? And why cannot it be serviced by astronauts? "James Webb Space Telescope is a prototype and with prototypes, you can always have something that goes wrong," Mark McCaughrean, senior advisor for science and exploration at the European Space Agency (ESA) and interdisciplinary scientist at the JWST science working group, told. With the James Webb Space Telescope, rescue missions are impossible and therefore no failures are allowed. Hubble received 'glasses' to correct its short-sightedness and turned into the astronomical powerhouse that has since generated thousands of iconic and scientifically priceless images. A rescue mission involving a team of astronauts was sent to fix the problem. The problem was traced to the telescope's great mirror, which was improperly polished during manufacturing. The images it sent to Earth were disappointing, blurry, nowhere near to what scientists had expected. When the Hubble Space Telescope launched in 1990, it soon became obvious something was amiss. The fault required an emergency crewed rescue mission. The James Webb Space Telescope's predecessor, the Hubble Space Telescope was infamously launched with an improperly polished mirror.
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