Written and edited by Toby Yu
On the left is the James Webb Space Telescope, and on the right is the Hubble Space Telescope.
For almost 32 years, the Hubble Space Telescope has been orbiting the Earth, travelling at a speed of 27300 kilometres per hour, taking 95 minutes to complete a full orbit around the Earth. It is positioned at an incline of 28.5 degrees to the equator, at an altitude of about 547 kilometres.
Hubble is a cassegrain telescope, which works by reflecting light off a series of mirrors and into its science instruments. Currently housed are 5 science instruments: the Wide Field Camera 3 (WFC3), Cosmic Origins Spectrograph (COS), Advanced Camera for Surveys (ACS), Space Telescope Imaging Spectrograph (STIS), and Fine Guidance Sensors (FGS). (“Telescope quick facts”, n.d.)
The remarkable Hubble Space Telescope has supported astrologists in so many ways, including the discovery of two moons, the determination of the universe’s expansion rate, and the age of the universe as a whole (about 13.8 billion years). If the Hubble Space Telescope has already provided us with so much, what is the purpose of the James Webb Space Telescope?
Webb is not a replacement for Hubble, but its successor. They were not made for the same purpose, nor do they have the same technical capabilities, with their main difference being what wavelength they observe in. Webb is able to observe wavelengths in the range of 0.6 to 28 micrometres, and as the infrared wavelength band in the electromagnetic spectrum range from 0.75 to 1 micrometre, Webb’s main function is to observe infrared light. Hubble is able to observe wavelengths in the range of 0.8 to 2.5 micrometres, and as the visible and ultra-violet bands in the electromagnetic spectrum range from 0.1 to 0.8 micrometres, Hubble’s main function is to observe visible and ultra-violet light. (“Webb vs Hubble”, n.d.)
These are both photographs captured by Hubble. The image on the left shows the Monkey Head Nebula in visible light, and the image on the right shows it in infrared light, accentuating the difference between what can be seen with instruments made to record visible and infrared light.
Image source: (“Webb vs Hubble”, n.d.)
Another main difference between the two telescopes is the size of their mirrors. As they are both cassegrain telescopes, the size of their field of vision entirely depends on the size of their mirrors. The size of Webb’s mirror is about 6.5 metres in diameter, and the size of Hubble’s mirror is about 2.4 metres in diameter. This equates to their collecting areas being 264 square metres and 4.5 square metres respectively, which is an obvious large difference.
The difference between the size of the Hubble Space Telescope’s primary mirror and the James Webb Space Telescope’s primary mirror.
Image source: (“Webb vs Hubble”, n.d.)
Aside from the difference in their instruments’ target wavelengths and the size of their mirrors, there are countless other differences between both telescopes, both of which will continue to provide scientists with the information needed to support new discoveries.
References
Telescope quick facts. (n.d.). https://hubblesite.org/quick-facts/
telescope-quick-facts
Webb vs Hubble telescope. (n.d.). https://www.jwst.nasa.gov/content/about/
comparisonWebbVsHubble.html
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