Artist concept of NASA's James Webb Space Telescope shortly after launch on its European Ariane 5 launch rocket. (ESA/D. Ducros)
NASA is performing the final physical exam on its James Webb Space Telescope, the long-awaited successor of the venerable Hubble Space Telescope.
The agency will launch the telescope on a European Ariane 5 rocket from French Guiana, sending it into space on a historic mission to probe currently unobservable reaches of our universe.
Originally scheduled to launch on Dec. 18, NASA experienced a hiccup during its launch preparations — what the agency is describing as an “incident” — and delayed liftoff until no earlier than Dec. 22 to give engineers time to ensure flight readiness.
The telescope’s destination is a million miles from Earth, a long voyage to a lofty vantage point from where it will peer farther into the universe than we have ever seen.
The observatory is named after James E. Webb, who led NASA from 1961 to 1968.
A high bar for discovery
The Hubble Space Telescope has operated for over three decades, orbiting close to home at roughly 300 miles from Earth’s surface and setting a high bar for future space discovery.
The telescope made thousands of observations with its 2.4-meter telescope, delivering jaw-dropping revelations about the size, age, expansion, and evolution of the universe. As well as the birth and death of stars, the formation of planets, and many hidden wonders spread across our own solar system. It’s fair to say that no other observatory, ground- or space-based, has revealed more about the cosmos than Hubble.
The James Webb telescope mirror is much larger than Hubble’s at 6.5-meters and can collect over five times the amount of light, enabling it to probe distances and scales of the universe where Hubble sees only darkness.
Telescopes let us look back in time, since it takes the light emitted by distant objects time to reach us. Hubble captured images of distant galaxies as they appeared about 13.5 billion years ago, when the universe — which Hubble itself determined to be 13.8 billion years old — was still in the early stages of forming galaxies.
The James Webb telescope will look further and deeper into the past, observing infant galaxies as they were only 200 million years after the universe was born in the Big Bang.
Within our galaxy, it will probe giant molecular clouds to see as never before how primordial star systems and planets formed, providing insight to how our own solar system and planet came to be.
And even closer to home, NASA’s new flagship space telescope will follow up on new discoveries of extrasolar planets by measuring their atmospheres, looking for signs of water and the chemical telltales of possible extraterrestrial life.
NASA developed the James Webb telescope in partnership with the European Space Agency and the Canadian Space Agency.
Not just a larger Hubble
NASA’s new telescope is different from Hubble in several ways.
While Hubble focused on the visible light emitted by stars, nebulas, galaxies and more, the Webb telescope will specialize in infrared astronomy, collecting and analyzing lower energy electromagnetic radiation. Not only will this allow the study of cooler objects and materials, like atmospheres of distant planets and clouds of gas and dust that give birth to new star systems, it will open a window on an infrared universe. Here, observations from Earth’s surface cannot access since the atmosphere blocks most wavelengths of infrared light.
Webb will not orbit Earth as Hubble does. Instead, it will circle the sun at Earth’s “L2” Lagrangian point, where the gravitational pull of Earth and sun cancel each other, forming a stable pocket of space where a spacecraft can loiter indefinitely. The location offers a double advantage, holding the observatory within easy communication range while keeping it away from Earth’s intense electromagnetic interference.
Engineers designed Webb’s primary mirror, which is almost three times the diameter of Hubble’s, to fit compactly within its launch rocket. The telescope’s light-collecting apparatus comprises 18 individual hexagonal mirrors that will be unfolded after launch during the monthslong journey to its destination.
Operators expect the observatory will be ready for scientific observations about six months after launch.
What will we see?
Back in 1995, researchers using the Hubble Space Telescope made an observation that expanded our vision of the universe.
They focused Hubble’s powerful eye on a patch of space where other observatories could perceive only darkness. The telescope zoomed in on a spot of sky no larger than Franklin Roosevelt’s eyeball on a dime’s surface and captured an image now known as the “Hubble Deep Field.”
This famous picture revealed over 3,000 distant, never-before-seen galaxies. From this image and others like it, astronomers were able to estimate that there are about 2 trillion galaxies within the observable universe.
Imagine what the far more discerning eye of the James Webb Space Telescope will reveal of the cosmos.
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