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JWST vs. Hubble: How are they different?

The wait is over. NASA finally released the first color science images from the James Webb Space Telescope on July 12. The initial release introduced the capabilities of the Observatory.

JWST builds on three decades of discoveries by the iconic Hubble Space Telescope. While JWST is sometimes called the replacement for Hubble, NASA considers it a successor.

What does that mean? As we celebrate the release of JWST’s stunning first images, let’s compare the two telescopes and explore what to expect from JWST’s images of the cosmos.

Is JWST a successor or a replacement for Hubble?

JWST was designed to pick up where Hubble left off in the study of the early universe. To understand how the two telescopes relate to each other, we need to go back to Hubble’s famous deep-field images.

These images are filled with countless shimmering galaxies and distant objects captured by Hubble after looking at the same piece of sky for several days. The oldest galaxies in deep-field images formed just 400 million years after the Big Bang.

But there are even older galaxies that have escaped Hubble’s detection. These galaxies are very distant, and due to the expansion of the universe, they are moving away from us so fast that the wavelengths of their light have shifted into the infrared, far beyond the capabilities of Hubble detection.

Scientists want to see these runaway galaxies, and that’s where JWST comes in. The telescope can see mid-infrared wavelengths that will allow it to spot galaxies born just 200 million years after the Big Bang. The first stars in these early galaxies produced the chemical building blocks of life as we know it – the very star stuff we are made of. By studying them, scientists will learn what the conditions were like shortly after the birth of the universe.

Hubble won’t last forever. In 2021, the observatory experienced a series of technical problems. When Hubble’s mission ends, JWST can step in – to some extent. Like Hubble, JWST is a versatile observatory that anyone can use.

Hubble sees ultraviolet light, visible light and a small slice of infrared. Although JWST is optimized for infrared, it overlaps Hubble quite a bit and can see red, orange and gold visible light.

JWST and Hubble also complement each other. Scientists will have the unprecedented opportunity to simultaneously observe objects with JWST and Hubble, bringing the cosmos to life in a wide range of light.

When was Hubble launched? When was JWST launched?

Hubble flew into low Earth orbit aboard the space shuttle Discovery on April 24, 1990, while JWST launched to a special place in deep space called L2 on December 25, 2021.

L2, officially known as the second Sun-Earth Lagrange point, is located 1.5 million kilometers (932,000 miles) from Earth, where the gravity of the Earth and the Sun balance each other. A spacecraft can orbit L2 using very little fuel and keep the Sun, Earth, and Moon behind indefinitely. This is what JWST will do.