Webb is an international collaboration between US space agency NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA), involving more than 10,000 people. Initially set for 2007, it finally took place on December 25, 2021, aboard an Ariane 5 rocket, from French Guiana. Then Webb's launch date was repeatedly postponed. The project was first conceived in the 1990s, but construction did not begin until 2004. This lets it peer further back in time than any previous telescope, to within a few hundred million years after the Big Bang, 13.8 billion years ago. Webb's infrared capabilities are what make it uniquely powerful-allowing it to detect light from the earliest stars, which has been stretched into infrared wavelengths as the Universe expanded. In astronomy, the farther out you see, the deeper back in time you're looking. Here, the gravity from the sun and Earth balance the centrifugal motion of a satellite, meaning it needs minimal fuel for course correction. It took the spacecraft almost a month to reach this region, called Lagrange Point two, where it remains in a fixed position behind the Earth and Sun to give it a clear view of the cosmos. Unlike the Hubble telescope which revolves around the Earth, Webb orbits around the Sun, nearly a million miles (1.6 million kilometers) from us, or four times the distance from our planet to the Moon. The mirror and the instruments are protected from the light of our Sun by a tennis-court sized thermal shield, made up of five superimposed layers.Įach layer is hair thin, and together they ensure the telescope operates in the darkness needed to capture faint glimmers from the far reaches of the Universe. The observatory also has four scientific instruments: cameras to take pictures of the cosmos, and spectrographs, which break down light to study which elements and molecules make up objects. The centerpiece of the observatory is its huge main mirror, measuring more than 21 feet (6.5 meters) in diameter and made up of 18 smaller, hexagonal-shaped mirrors. Here is an overview of this feat of human ingenuity, in five key figures.
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