NASA's James Webb Space Telescope has oftentimes been identified as a "Hubble replacement." However, the space agency prefers to call it the "scientific successor" to the latter, from which results from the former drove its goals.
A NASA report said the science of Hubble "pushed us back" to look to longer wavelengths to exceed what Hubble has already accomplished.
Specifically, more distant objects are said to be more highly shifted, and their light is pushed from the ultraviolet ad optical into what's described as the "near-infrared."
Therefore, for instance, these distant objects' observation, like the first galaxies formed in the Universe, requires an infrared telescope.
This is the other reason that Webb is indeed not Hubble replacement-its capacities are not alike. Primarily, Webb is designed to look at the Universe in the infrared. On the other hand, Hubble investigates it mainly at optical and UV wavelengths, even though it has some infrared capabilities, too.
Essentially, Webb has a much larger mirror compared to Hubble. This bigger light-collecting site means that the scientific successor can peer further back into time compared to What Hubble is capable of doing.
The space shuttle Atlantis' mission was to overhaul the Hubble Space Telescope in 2009 to extend its working life.
Different Wavelengths and Sizes
In terms of wavelengths, Webb is designed to observe mainly in the infrared and has four scientific instruments to capture images, not to mention spectra of astronomical objects. Such instruments will offer wavelength coverage from 0.6 to 28 micrometers.
The infrared portion of the electromagnetic spectrum goes from roughly 0.75 to a new hundred microns. Meaning, the instruments of Webb will work mainly in the electromagnetic spectrum's infrared range, along with some capability in the visible spectrum, specifically in the visible spectrum's red and up to the yellow portion.
Webb telescope is going to have a roughly 6.5-meter diameter main mirror, which would give it a substantially bigger collecting site than the mirrors available on the space telescopes' present generation.
Moreover, the mirror of Hubble is much smaller at 2.4 meters in diameter, and its corresponding collecting site is 4.5 m2, giving its successor roughly 6.25 times more collecting site.
Webb will have a considerably bigger field of view than Hubble's NICMOS camera, covering more than 15 times the site.
It also has a substantially better spatial resolution than what's available with the infrared Spitzer Space Telescope.
Difference in Orbit
Essentially, this planet is 150 million kilometers from the Sun, and the moon is orbiting the Earth at an approximately 384,00-kilometer distance.
The Hubble Space Telescope is orbiting around this planet at a 570-kilometer altitude on top of it. Webb, on the other hand, will not circle the Earth. Rather, it will sit at the Earth-Sun, 1.5 million kilometers away.
Since Hubble is in the orbit of Earth, it was successfully launched into space by the space shuttle. Meanwhile, Webb will be launched on an Ariane 5 rocket, and since it will not be in the orbit of Earth, it is not designed for the space shuttle's service.
At the L2 point, the solar shield of Webb will block the light coming from the Sun, Earth, and Moo. This will then help Webb remain cool, which is essential for an infrared telescope.
Related information about the difference between Hubble and Webb space telescopes is shown on The Secrets of the Universe's YouTube video below:
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