James Webb Space Telescope vs. Hubble: How will their images compare?

NASA's James Webb Space Telescope (JWST), will orbit the sun 1 million miles (1.5 million kilometers) from Earth. (Image credit: ESA)

NASA's James Webb Space Telescope is ready to go into space and become the most powerful telescope in space at the moment. Is it going to be better than Hubble's?




At some point in 1990, the Hubble Space Telescope took off. Over the last three decades, the famous observatory has helped us see more of the universe and kept us interested in the beautiful images it takes of the universe. In the beginning, it was hard to see what was beyond the horizon, but now the universe is full of stars and galaxies that have never been seen before.




That's not how the James Webb Space Telescope works. It will launch on December 24. A NASA fact sheet says that Webb has a huge gold mirror and other tools that can see things that are 10 to 100 times fainter than Hubble can see. It will be interesting to see how Webb's view will be different from Hubble's.




In the sheet, it says that the images Webb takes "will be detailed and spectacular."




Not a replacement telescope


It is common to say that Webb is Hubble's successor. That said, Hubble's science instruments have had a few problems over the years. The two big scopes are set to work together in space, though not very close together.




Webb will go a lot farther than Hubble. It will go 930,000 miles (1.5 million kilometers) away from Earth, called the Sun-Earth Lagrange point 2. (L2).




Also, Hubble and Webb are both big space telescopes, but Webb is much bigger than Hubble. The two telescopes look at the universe very differently.




At a news conference in May, Webb project scientist Klaus Pontoppidan said that "amazing images" will be taken by the telescope. They will be better than those taken by Hubble, he said. Even though Webb's images will be better in some ways, they'll also be "different," Pontoppidan said. That's because Webb will be taking pictures at different wavelengths.




Webb is designed to look for mostly infrared light, while Hubble looks for mostly optical and ultraviolet light.




Infrared beauty


Webb will look at things in infrared to get unique and beautiful images.




He said, "I think it will be great, but I can't say for sure how it will look because this is the first space telescope mission of its kind."


These are two images taken by the Hubble Space Telescope, one (left) viewing the Carina Nebula in visible light and the other (right) seeing it in infrared.  (Image credit: NASA/ESA/Hubble 20th Anniversary Team)


He said that it would look very, very different from Hubble. Stars fade away when you go to a longer wavelength, but interstellar clouds get brighter and brighter and brighter as you go.




It gets a little wispy as you move into the infrared light range, Pontoppidan said. But that's not always a bad thing.




Then, Pontoppidan said, "I think maybe there was some worry that you know, you don't want images that look wispy." "That's not the whole story, though. If you go a little further out into infrared, the dust itself glows in the heat. You get a very bright nebula, like a star."


This Hubble image, captured and released to celebrate the telescope’s 23rd year in orbit, shows part of the sky in the constellation of Orion (The Hunter) in infrared light. Rising like a giant seahorse from turbulent waves of dust and gas is the Horsehead Nebula, otherwise known as Barnard 33. Image released April 19, 2013. (Image credit: NASA/ESA/Hubble Heritage Team (AURA/STScI))



Infrared differences


Hubble can see about 200 nanometers (nm) to 2.4 microns of light. According to the fact sheet, Webb will see the light with a wavelength of about 600 nm to 28 microns. Visible light has a wavelength of about 700 to 400 nm.




Even though Webb is mostly used to looking at infrared light, it will still see the red and orange parts of the visible light spectrum. As you look at it, visible blue light is absorbed by a layer of gold on its mirrors. But it also reflects yellow and red visible light that people will see.




Hubble can look at some infrared, even though it isn't its main job. This type of observation isn't a complete change. There was even a stunning image of the Horseshoe Nebula taken by Hubble in 2013 to celebrate its 22nd birthday.




The power of infrared


Hubble has been giving the world amazing images for years, and Webb has the same level of sharpness. A fact sheet says Webb will have the same angular resolution as Hubble. The sheet says that Webb images will look just as good as Hubble's do, and they will be as clear. At 24 miles (40 km), NASA says, Webb's resolution would allow it to see everything about an object's size of a US penny.




Webb has a 21.3 feet (6.5 meters) wide mirror compared to Hubble's 7.8 feet (2.4 meters) wide. It also has new detectors and can see farther into the infrared spectrum than Hubble can.




Webb will be able to look at the universe in infrared, which will allow scientists to see a lot farther into the universe, NASA says. It also has a bigger mirror, which allows it to look even farther into space. This allows scientists to look back in time and see the universe billions of years ago.




Webb was made to see the first stars and galaxies that ever existed in the early universe. This means that it can look back in time. It can see objects 10 billion times fainter than the faintest stars you can see with your eyes, or 10 to 100 times fainter than Hubble can see.




To make its observations, Webb has four scientific instruments on board that it can use. Some of these are the Near Infrared Camera (NIRCam), the Near-Infrared Spectrograph (NIRSpec), and the Mid-Infrared Instrument (MIRI) (FGS-NIRISS).




Webb can use these tools to do "imaging spectroscopy," Pontoppidan said. "Where it can take an image, but it will also take a spectrum and every pixel of the image as well," he said. This is called imaging spectroscopy, and it tells you how many different wavelengths are in each small piece of the image. Scientists can use this to figure out what elements or chemicals might have made that color or sound range.




The Webb telescope has a unique set of imaging tools that can do a lot of other things, like look for exoplanets transiting in front of stars or figure out the composition of clouds in a star-forming region. For example, he said, studies could look for ice, water, and complex organics in the atmospheres of exoplanets.




As part of a project with the help of NASA, the European Space Agency, and Canada's Space Agency, the James Webb Space Telescope has been built.




After an extra delay, Webb is still on track to launch on December 24, 2021, from Europe's Spaceport in Kourou, French Guiana. It will be on an Arianespace Ariane 5 rocket from the spaceport.

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