NASA’s James Webb Space Telescope is currently set to launch and become the most powerful telescope in space. But how will its photos compare to those of Hubble?
The Hubble Space Telescope was launched into low Earth orbit in April 1990. Over the next three decades, the famed observatory has broadened our view of the cosmos and captured our attention with the stunning images it collects. What was once a faint and mysterious abyss became a detailed and colorful universe, and we got to see stars and galaxies like they had never been seen before.
But the James Webb Space Telescope, set to launch on December 24, will do things a little differently. With his giant golden mirror and infrared light observation tools, Webb is designed to “see” objects 10 to 100 times fainter than what Hubble can see, according to a NASA fact sheet. So how will Webb’s view compare to Hubble’s?
One thing is certain: the images Webb will capture “will be detailed and spectacular,” according to the listing.
Live updates: Launch of NASA’s James Webb Space Telescope
Not a replacement telescope
Webb is often described as Hubble’s replacement or successor. But despite a handful of glitches over the years, Hubble’s science instruments are still performing well, and the two large oscilloscopes are ready to observe together (albeit far apart) in space.
Hubble is fairly close to us in low Earth orbit, but Webb will travel much farther, to a gravitationally stable point 1.5 million kilometers from Earth known as Sun-Earth Lagrange Point 2 (L2).
Also, while Hubble and Webb are both large space telescopes (although Webb is considerably larger), they both “see” the universe very differently.
“It will take some incredible images; they will be better than what Hubble did,” Klaus Pontoppidan, Webb project scientist at the Space Telescope Science Institute in Baltimore, told a press conference in May. But, while better in some ways, Webb’s images will also be fundamentally “different, because they’re different wavelengths,” Pontoppidan said.
While Hubble observes light primarily in optical and ultraviolet wavelengths, Webb is designed to primarily detect infrared light.
By observing in the infrared, Webb will capture images of unique beauty.
“I think it will be fantastic,” Pontoppidan said, “but it’s very difficult to predict what it will look like,” because it will be the first such space telescope mission.
“It will be very, very different from Hubble,” Pontoppidan said. “The stars themselves are fading, they’re getting dimmer and dimmer [when you] go to [a] longer wavelength, but interstellar clouds are getting brighter and brighter.”
Some gas and dust features get a bit wispy as you start to move into the infrared part of the spectrum, Pontoppidan explained. But that’s not necessarily a bad thing.
“I think there was maybe some concern that, you know, you don’t want images that end up looking wispy,” Pontoppidan said. “But it turns out that actually, if you go just a little deeper into the infrared… the dust itself lights up in thermal light. You get a glowing nebula.”
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Differences in the infrared
Hubble can see light in a wavelength range of around 200 nanometers (nm) to 2.4 microns, while Webb’s range will go from around 600 nm to 28 microns, according to the fact sheet, which adds that visible light varies from about 700 to 400 nm.
Even though Webb primarily observes infrared light, he will still be able to see the red/orange portion of the visible light spectrum. The gold coating of its mirrors absorbs blue light from the visible spectrum, but it reflects yellow and red visible light that will be detected.
Although not its primary observing function, Hubble also has the ability to observe some infrared, so this type of observing is not a complete departure. Indeed, in 2013, the Hubble team posted a great infrared image of the Horsehead Nebula captured by the space telescope to celebrate the 22nd anniversary of its launch.
Related: Construction of the James Webb Space Telescope (gallery)
The power of infrared
Hubble has provided the world with stunning images for decades and has a sharpness similar to that of Webb. “Webb’s angular resolution, or sharpness of view, will be the same as Hubble’s,” according to the fact sheet. “Images from Webb will appear as sharp as those from Hubble,” the sheet says. According to NASA, Webb’s resolution would allow him to see details of an object the size of a US penny 40 km away.
Despite this similarity, Webb has a much larger mirror – 21.3ft (6.5m) wide, compared to 7.8ft (2.4m) – of the edge detectors and is designed to see deeper into the infrared spectrum than Hubble.
By observing in the infrared, Webb will allow scientists to see much farther into the universe, NASA explained. Its larger mirror also gives it more surface area to collect light, allowing the scope to look even farther out into space, essentially allowing scientists to look “back in time” at the universe of billions. years in the past.
Webb was designed to be able to “see” the first stars and galaxies that formed in the early universe. It can detect objects 10 billion times fainter than the faintest stars visible without a telescope, or 10 to 100 times fainter than what Hubble can observe.
Webb is equipped with four scientific instruments to help him make his observations. These include Near Infrared Camera (NIRCam), Near Infrared Spectrograph (NIRSpec), Mid Infrared Instrument (MIRI), and Fine Guidance Sensor/Near Infrared Imager and Slitless Spectrograph (FGS-NIRISS) .
With these tools, Webb “can do what we call imaging spectroscopy,” Pontoppidan said, “where he can take an image, but he’ll also take a spectrum and every pixel in the image.” In imaging spectroscopy, there is information about the spectrum of wavelengths present in every tiny piece of the image. This can help scientists figure out what elements or chemicals might have created this spectrum.
Pontoppidan added that Webb’s unique suite of imaging tools will allow him to perform all sorts of other scientific work, such as observing exoplanets transiting in front of stars or determining the composition of a cloud. in a star forming region; he pointed to studies that could look for ice, water and complex organic compounds in the atmospheres of exoplanets.
The James Webb Space Telescope is a joint effort involving NASA, the European Space Agency and the Canadian Space Agency.
After additional delay, Webb is still on track to launch on December 24, 2021, atop an Arianespace Ariane 5 rocket from Europe’s spaceport in Kourou, French Guiana.