After decades of waiting, the James Webb Space Telescope, the most powerful space observatory ever built, is now ready for launch on Christmas Day. An engineering marvel, it will help answer basic questions about the universe, dating back 13 billion years in time. Know here five things.
giant gold mirror
The telescope’s centerpiece is its massive primary mirror, a concave structure 21.5 feet (6.5 m) wide and made up of 18 smaller hexagonal mirrors. They are made of beryllium coated with gold, adapted to reflect infrared light from the far reaches of the universe. The observatory also houses four scientific instruments, which together serve two main purposes: imaging of cosmic objects, and spectroscopy – breaking down light into different wavelengths to study the physical and chemical properties of cosmic matter.
The mirrors and instruments are protected by a five-layer sunshield, shaped like a kite and built to the size of a tennis court. Its membrane is made of kapton, a material known for its high heat resistance and stability under a wide temperature range – both important, as the sun-facing side of the shield can be as high as 230 °F (110 °C). Will heat up, while the other side reaches as low as -394F.
The telescope also has a “spacecraft bus” which includes subsystems for electrical power, propulsion, communication, orientation, heating, and data handling; All told, the web weighs almost as much as a school bus.
a million miles
The telescope will be placed in orbit at a distance of about one million miles from Earth, which is about four times the distance of our planet from the Moon. Unlike Hubble, the current major space telescope that revolves around the planet, Webb will orbit the Sun. It will be directly behind Earth in the view of the Sun, making it the night side of our planet. Webb’s sunshield will always be between the mirror and our star.
It will take about a month in space to reach this region, known as the second Lagrange point, or L2. While astronauts have been sent to repair Hubble, no humans have ever traveled to Webb’s planned orbit.
hi-tech origami
Because the telescope is too large to fit into the nose cone of the rocket in its operational configuration, it has to be carried folded, origami style. Unfurling is a complex and challenging task, one of the most difficult deployments NASA has ever attempted.
About 30 minutes after take-off, the communications antenna and the solar panels that power it will be deployed. This is followed by the hoisting of the Sun’s shield, still bent like an accordion, starting on the sixth day, after crossing the Moon. Its thin membranes will be guided by a complex mechanism consisting of 400 pulleys and 1,312 feet of cable.
During the second week it will finally be the time for the mirror to open. Once in its final configuration, the instruments will need to be cooled and calibrated, and the mirrors adjusted very precisely. After six months the telescope will be ready to go.
Life, the Universe, and Everything
Webb has two primary scientific missions, which together will account for more than 50 percent of its observation time. First, let’s trace the earliest stages of cosmic history, a few hundred million years after the Big Bang. Astronomers want to see how the first stars and galaxies formed and how they evolved over time.
Its second major goal is the search for exoplanets, which means planets outside the Solar System. It will also study the environments of those worlds to investigate the possibility of life on them. Webb’s great promise lies in its infrared capability.
Unlike ultraviolet and visible light Hubble mostly operates on, longer wavelengths of infrared penetrate dust more easily, allowing the early universe enveloped in clouds to be seen more clearly. Infrared lets scientists go further back in time because of a phenomenon called redshifting. Light from distant objects expands as the universe expands, toward the infrared end of the spectrum.
Closer observations of Mars and Europa, Jupiter’s icy moon in our solar system, are also planned.
decades in the making
Astronomers began debating the telescope that succeeded Hubble in the 1990s, beginning with Webb’s construction in 2004. The launch was pushed back several times, initially penciled in for 2007, then 2018 … mainly due to complications associated with development. The observatory is the result of a vast international collaboration, and integrates Canadian and European instruments.
More than 10,000 people worked on the project, with the budget eventually reaching about $10 billion. The mission is set to last at least five years, but hopefully 10 or more.
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