"It will take amazing images they will be better than what Hubble did," Klaus Pontoppidan, Webb project scientist at the Space Telescope Science Institute in Baltimore, said during a news conference in May. Hubble is pretty close to us in low Earth orbit, but Webb will travel out much farther, to a gravitationally stable spot 930,000 miles (1.5 million kilometers) from Earth known as the Sun-Earth Lagrange point 2 (L2).Īdditionally, while both Hubble and Webb are large space telescopes (though Webb is considerably bigger), the two actually "see" the universe very differently. But despite a handful of glitches over the years, Hubble's science instruments are still going strong, and the two big scopes are set to observe together (albeit far apart from one another) in space. Webb will constantly face the nightside of Earth as the spacecraft and planet swoop around the sun in unison.Webb is often described as Hubble's replacement or successor. This is where the gravitational forces of the Earth and sun balance, requiring minimal fuel for a spacecraft to stay put. Webb is bound for more a more distant spot - 1 million miles (1.6 million kilometres) away at what’s called the second Lagrange point. The altitude was dictated by the capabilities of Nasa’s space shuttles, which delivered Hubble to orbit and then made five service calls. Hubble circles 330 miles (530 kilometres) overhead. Each of the 18 hexagonal segments are the size of a coffee table and coated with ultra-thin gold, an ideal reflector of infrared light. It’s also segmented, allowing it to fold like a drop-leaf table for launch. That’s because Webb’s mirror is made of beryllium, a strong but lightweight metal. The mirror spans more than 21 feet (6.5 meters), yet is lighter than Hubble’s, which is 8 feet (2.4 meters) across. To discern the universe’s first, faint stars, Webb requires the largest mirror ever launched for astronomy. Multiple layers also better protect against micrometeorite hits. Between each of the sunshield’s five layers is a gap so heat can escape out the sides. To stay chilled, Webb carries a parasol the size of a tennis court. That’s why Webb’s detectors need to run at minus 400 degrees Fahrenheit (minus 240 degrees Celsius). The shorter visible and ultraviolet wavelengths emitted by the first stars and galaxies have been stretched as the universe expands, so Webb will see them in their elongated, heat-emitting infrared form. Webb has infrared vision, allowing it to pierce cosmic clouds of dust. Hubble sees what we see - visible light - with a little ultraviolet and infrared thrown in. “It’s like looking at the picture book of my kids and missing the first two years, right? Trying to figure out where they come from,” said Nasa science chief Thomas Zurbuchen. Astronomers are eager to close the 300 million year gap with Webb and draw ever closer in time to the Big Bang, the moment the universe formed 13.8 billion years ago. Hubble has stared as far back as 13.4 billion years, disclosing a clumpy runt of a galaxy that is currently the oldest and farthest object ever observed. This light will reveal how the original stars looked 13.7 billion years ago. Webb is expected to behold light from the universe’s first stars and galaxies, beyond Hubble’s range.
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