James Webb Space Telescope (JWST)

Context

• The James Webb Space Telescope is scheduled to be rocketed into orbit no earlier than December 22. 
• The Webb telescope is said to be the scientific successor to the Hubble Space Telescope.

About JWST

• It will be a large infrared telescope with an approximately 6.5-meter primary mirror.  
• The telescope will be launched on an Ariane 5 rocket from French Guiana in 2021.
• It was formerly known as the Next Generation Space Telescope (NGST) but was renamed in 2002 after a former NASA administrator, James Webb.
  • Under his tenure, NASA launched over 75 space science missions, including probes that were sent to Mars and Venus.
• Purpose : 
  • It will study every phase in the history of the Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of the Solar System.

• Partners:

• It is an international collaboration between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).
• The NASA Goddard Space Flight Center is managing the development effort.

• Main Features:
  • These include a primary mirror made of 18 separate segments that unfold and adjust to shape after launch. 
    • The mirrors are made of ultra-lightweight beryllium. 
  • Webb’s biggest feature is a tennis court-sized five-layer sunshield that attenuates heat from the Sun more than a million times.
  • It has a cryocooler for cooling the mid-infrared detectors of other instruments. 

                  Image Courtsey: NASA

• Wavelengths: Visible, Near Infrared, Mid Infrared (0.6-28.5 micrometres)
• Location in space: Orbiting the Sun around the second Lagrange point (L2)

• It will be the largest, most powerful and complex space telescope ever built and launched into space.

Webb vs other space telescopes

• Webb and the Hubble Telescope.
  • The James Webb Space Telescope, carrying four scientific instruments, will observe primarily in the infrared range and provide coverage from 0.6 to 28 microns. 
    • The instruments on Hubble see mainly in the ultraviolet and visible part of the spectrum. It could observe only a small range in the infrared from 0.8 to 2.5 microns.
    • The infrared region of the electromagnetic spectrum covers the wavelength range from approximately 0.7 to a few 100 microns.

• Size comparisons: Webb’s primary mirror has a diameter of 6.5 metres. Hubble’s mirror was much smaller – 2.4 metres in diameter.
  •  So, Webb will have a larger field of view compared to the camera on Hubble.
  • Webb also carries a large sun shield measuring about 22 metres by 12 metres – about the size of a tennis court.

• Orbit: Hubble orbits around the Earth at an altitude of ~570 km. 
  • Webb will not orbit the Earth. 
    • It will orbit the sun at about 1.5 million kilometres away from Earth. As the Earth orbits the Sun, Webb will orbit with it – but it will stay fixed in the same spot with relation to the Earth and the Sun.
• Visibility:  Hubble can see the equivalent of “toddler galaxies” and Webb Telescope will be able to see “baby galaxies”.”
  •  Webb’s near- and mid-infrared instruments will help study the first formed galaxies, exoplanets and birth of stars.

• Webb vs Herschel Space Observatory
  • In 2009, the European Space Agency launched an infrared telescope named the Herschel Space Observatory.
  • It also orbits the Sun similar to how Webb would. 
    • The primary difference between Webb and Herschel is the wavelength range: Webb goes from 0.6 to 28 microns, while Herschel covers 60 to 500 microns.
  • Also, Herschel’s mirror is smaller than Webb’s. It is 3.5 metres in diameter, while Webb’s primary mirror has a diameter of 6.5 metres.
  • Another large infrared telescope — the Herschel Space Observatory — built and operated by the European Space Agency was active from 2009 to 2013.
  • But Webb and Herschel are complementary. 
  • Webb will be sensitive to wavelengths from visible light to mid-infrared, while Herschel was sensitive in the far-infrared wavelength.

• Webb vs  Kepler telescope
  • The Kepler telescope launched in 2009 and retired in 2018 helped identify planets that are located in or near the habitable zone of other stars.
    • Kepler was “designed to be a “wide and shallow” survey telescope, while Webb is designed for “narrow and deep” focused studies with near and mid-IR imaging and spectroscopy.”

Source: IE