Peering at the edge of the universe

NASA is preparing to launch the most powerful space telescope ever. What will it see? Here’s everything you need to know:

Why a new space telescope?

The James Webb Space Telescope will be 100 times more powerful than its predecessor, Hubble, and will be capable of capturing extremely faint infrared light from the very first galaxies at the edge of the universe. It will also be able to study planets around other stars in our own galaxy, examining their atmospheres for telltale signs of life. Originally scheduled to launch in 2010 and cost about $1 billion, Webb — a joint venture among U.S., European, and Canadian space agencies that took 10,000 people to construct — experienced a sequence of maddening delays as costs ballooned to $10 billion. But the colossal telescope finally has been shipped to French Guiana in South America, where it will be fitted onto a rocket and blasted into space on Dec. 18, beginning the most technically ambitious mission in NASA history. Should Webb successfully reach its destination nearly a million miles from Earth, the telescope will earn its nickname “First Light Machine,” as it sends back images of stars formed just 250 million years after the Big Bang. “It’s going to help us unlock some of the mysteries of our universe” and “rewrite the physics books,” says Greg Robinson, Webb’s program director at NASA.

How does it work?

The telescope utilizes several novel technologies. It relies on a 21-foot mirror made of ultra-lightweight beryllium chiseled into 18 hexagonal segments and coated with gold. Unlike most telescopes, which house a mirror or lens within a tube to block out light, Webb’s mirror will be exposed to open space, relying on five parasol-like sheets of aluminum-coated plastic — each as thin as notebook paper and as big as a tennis court — to block out light and heat from the sun, moon, and Earth. Webb includes four solar-powered cameras and sensors to collect data.

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How does Webb differ from Hubble?

Hubble, launched in 1990, sent back dazzling images from deep space, and helped astrophysicists better determine the age of the universe, the nature of black holes, and the number of galaxies. It also led to the discovery that, thanks to “dark energy,” the universe is expanding at an accelerating rate. That’s where Webb comes in. By the time light from a 13 billion–year-old star reaches Earth, the expansion of the universe has stretched the light’s wavelength into the infrared spectrum, similar to how a siren’s pitch drops as an ambulance speeds away. For that reason, only an infrared-focused telescope is capable of peering into the “cosmic dawn.” Webb uses mirrors that capture six times more light than Hubble’s, and cameras with a 15-times-wider view. Hubble orbits the Earth at an altitude of 340 miles. Webb will be positioned out in space, roughly four times farther away from the Earth than the moon, for maximum light-gathering.

How does it get to space?

First, the 14,330-pound telescope must be folded, origami-style, to fit atop an Ariane 5 rocket. After about 30 minutes of flight, the telescope will be ejected from the rocket. “That’s when…