Don’t ask astronomers to choose between the Hubble Space Telescope and the new kid on the cosmic block, the James Webb Space Telescope. “Comparing Hubble and Webb is like asking whether you’ll love your second child more than your first,” said Susan Mullally, Webb’s deputy project scientist at the Space Telescope Science Institute in Baltimore.
“Hubble will always be loved for its awe-inspiring images of our universe and will continue to collect important data for astronomers. Webb gives us new and unique eyes of places we have never been able to reach.”
With NASA and the European Space Agency’s Hubble advancing 32 years in orbit, the larger, 100-times more powerful Webb is widely seen as its successor, even though the two are very different. Its lift-off is scheduled for Saturday morning off the coast of South America.
Hubble caught a lift to orbit inside the NASA spacecraft Discovery in 1990. It quickly ran into trouble: One of the telescope’s solar wings got jammed due to flapping. The astronauts were fit for an emergency spacewalk, but Earth orders freed the panel. Within weeks, Hubble’s blurred vision was detected. Spacewalking astronauts fixed it three years later. Soaring from South America on a European Ariane rocket, Webb would be inaccessible by astronauts at its destination 1 million miles (1.6 million kilometers) away. Bigger and more complex than Hubble, Webb would be a goner if its foldout mirror and sunshield snarled.
Webb is expected to see light from the universe’s first stars and galaxies beyond the limits of Hubble. This light would explain how the original stars looked 13.7 billion years ago. Hubble has observed 13.4 billion years ago, revealing a clustered part of a galaxy that is currently the oldest and most distant object ever observed. Astronomers are eager to close the 300 million-year gap with Webb and approach the time of the Big Bang, the moment the universe formed 13.8 billion years ago. “It’s like looking at my kids’ picture book and remembering the first two years, right? Trying to figure out where they come from,” said Thomas Zurbuchen, NASA’s chief of science.
Hubble captures what we see – visible light – with a little ultraviolet and infrared. Webb has infrared vision, which allows it to penetrate cosmic clouds of dust. The shorter visible and ultraviolet wavelengths previously emitted by stars and galaxies have been amplified as the universe expands, so Webb will see them in their expanded, heat-emitting infrared form. So Webb’s detectors need to run at minus 400 degrees Fahrenheit (minus 240 degrees Celsius). To stay cool, Webb maintains a parasol the size of a tennis court. There is a gap between each of the sunshield’s five layers to allow heat to escape from the sides. Multiple layers also better protect against micrometeorite hits.
To understand the universe’s first, faint stars, Webb needs the largest mirror ever launched for astronomy. The mirror spans over 21 feet (6.5 m), yet is lighter than Hubble, which is 8 feet (2.4 m) across. This is because Webb’s mirror is made of beryllium, which is a strong but lightweight metal. It’s also segmented, allowing it to fold like a drop-leaf table for launch. Each of the 18 hexagonal sections is the size of a coffee table and coated with ultra-thin gold, a perfect reflector of infrared light.
Hubble circles 330 miles (530 kilometers) overhead. The altitude was determined by the capabilities of NASA’s Space Shuttle, which carried Hubble into orbit and then made five service calls. Webb is bound for a more distant location – 1 million miles (1.6 million kilometers) away called the second Lagrange point. This is where the gravitational forces of Earth and the Sun balance, allowing the spacecraft to require minimal fuel to stay afloat. Webb will continually face the night side of Earth as the spacecraft and the planet simultaneously swoop around the Sun.
By the time Hubble entered orbit in 1990, Hubble was years late and had a budget of millions. The web has also come years late with great costs. NASA’s tab for Hubble since 1970s development: $16 billion, adjusted for inflation. This does not include all shuttle flights for launch and repair. The web’s price tag is estimated at $10 billion; Including the first five years of operation. The European Space Agency is bearing launch costs from French Guiana with a French-built Ariane rocket providing Webb’s lift.
Astronomer Edwin Hubble confirmed a century ago that countless galaxies exist beyond our Milky Way and that the universe is constantly expanding. James Webb led NASA from 1961 to 1968, presiding over projects Mercury and Gemini, and in the early stages of Apollo’s moon-landing program. In 2002, a decade after Webb’s death, NASA chose his name for the new telescope. But now some scientists and others want a new name, given Webb’s leadership of the State Department and NASA during the Truman administration, when government employees were fired for being gay. Administrator Bill Nelson said a NASA historian conducted an archival search of Webb this year, but found no evidence of the name change.
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