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How Webb and Hubble space telescopes are different

Canadian scientists will be some of the first to study data collected by the most advanced space telescope ever built

The Webb and Hubble space telescopes are different, but they complement each other in several ways. The James Webb Space Telescope will be Hubble’s successor, but not its replacement. The two missions have a planned overlap and will work together on new discoveries. Webb will build on Hubble’s impressive legacy by helping humanity peer even deeper into the universe according to the Canadian Space Agency, one of three agencies including the European Space Agency and NASA that are launching JWST on December 25th.

Canadian CSA astronaut David Saint-Jacques and astrophysicist Sara Gallagher weighed in on those differences.

David Saint-Jacques: How are the mission and capabilities of Webb different from those of Hubble?

Sara Gallagher: There are many differences between Hubble and Webb.

Webb is larger than Hubble. Its primary mirror is 6.5 metres wide, and Hubble’s is 2.4 metres wide.

That makes a big difference, because a mirror is basically a light bucket, and the more light you capture, the more sensitive you are to things that are really, really faint and far away. That means that Webb can see farther into the cosmos.

Webb’s location is also much farther away in space, 1.5 million kilometres from Earth orbiting the Sun at a point known as Lagrange 2. But Hubble is in low Earth orbit, which is only about 550 kilometres away.

The reason it’s great that Webb is so far away is that it gives us an unobstructed view of the sky because you don’t have to worry about the Earth getting in the way. Webb and Hubble are also looking into different types of light. So Webb is designed to focus on the near- and mid-infrared parts of the spectrum. And Hubble uses mostly visible and ultraviolet light.

About James Webb Space Telescope

The James Webb Space Telescope will be the most important space observatory of the next decade, serving astronomers from all over the world. It is an international collaboration between NASA, the European Space Agency and the Canadian Space Agency (CSA).

The CSA is contributing two important elements, built by Honeywell, to the Webb Telescope:

  • the Fine Guidance Sensor (FGS), which will allow the telescope to point at and focus on objects of interest
  • the Near-Infrared Imager and Slitless Spectrograph (NIRISS), a scientific instrument that will help study many astronomical objects, from exoplanets to distant galaxies

In exchange, Canada will receive a guaranteed share of Webb’s observation time, making Canadian scientists some of the first to study data collected by the most advanced space telescope ever built.

The Fine Guidance Sensor (FGS) is the most sophisticated guidance sensor of any telescope ever built. It locks on to bright stars in deep space to keep Webb’s images sharp. (Credit: Canadian Space Agency)

On December 25, the James Webb Space Telescope is planned to launch from Europe’s Spaceport in French Guiana. The live coverage of the launch is available on NASA TV (starting at 6:00 a.m. ET. The launch is scheduled for 7:20 a.m. ET. More information


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