At the end of June, NASA boss Bill Nelson promised “the deepest image ever taken of our Universe”.
>> So far, the deepest image of the Universe, is the one taken by the Hubble Space Telescope:
This view of nearly 10,000 galaxies is called the “Hubble Ultra Deep Field”. The snapshot includes galaxies of varying ages, sizes, shapes, and colors. The smallest and reddest galaxies, around 100, could be among the most distant known, existing when the Universe was only 800 million years old. The nearest galaxies – the larger, brighter, well-defined spirals and ellipticals – developed around 1 billion years ago, when the Cosmos was 13 billion years old. The image required 800 exposures taken during Hubble’s 400 orbits around Earth. The total exposure time was 11.3 days, between September 24, 2003 and January 16, 2004. [S. Beckwith (STScI) and the HUDF Team – NASA/ESA]
>> Read also: Hubble went back 500 million years after the Big Bang
The images must both impress the general public with their beauty, but also demonstrate to astronomers around the world the full power of onboard scientific instruments. It is for this reason that they targeted a variety of cosmic objects.
Experts will thus be able to get an idea of what James Webb is capable of, and practice interpreting the data collected, using dedicated software, giving the starting signal for a great scientific adventure: “When I saw the images for the first time (…), I suddenly learned three new things about the Universe that I did not know before”, confided Dan Coe, astronomer at the institute of Baltimore, and one of the lucky few in the confidence. “It completely blew me away.” James Webb will “transform our understanding of the Universe”, he testified.
In colors
The names of the cosmic objects observed are just as poetic as they are enigmatic: the carina nebula and of thesouthern ring – gigantic clouds of gas and dust where stars are formed –, the Stephan Quintet – a compact grouping of galaxies.
Another target, the cluster of galaxies SMACS 0723, acting as a magnifying glass allowing to see the faint lights behind it, even further: it is called a gravitational lens.
Galaxy cluster SMACS 0723 is a gravitational lens. Thanks to him, it is possible to see the faint lights behind him, even further. [archive.stsci.edu]
The probably majestic colors that will be revealed in the photographs will not, however, be directly those observed by the telescope.
Light breaks down into different wavelengths, and James Webb works in infrared, which the human eye cannot perceive. Infrared light is also rich in colors, but not being in the visible spectrum, these will therefore be “translated” into colors that we can distinguish.
The light spectrum. The JWST sees in the near and mid infrared. [Œuvre INRS – inrs.fr]
Thanks to these observations in the near and mid-infrared, James Webb will be able to see through impenetrable clouds of dust for his predecessor, the mythical Hubble Space Telescope. Launched in 1990 and still in operation, it has a small infrared capacity but operates mainly in visible light and ultraviolet.
>> Browse astronomical images captured at different wavelengths of light and note what each reveals and conceals: Infrared video gallery
“Even when Hubble managed to take the image of a distant galaxy, it was not able to distinguish a squirrel from an elephant”, summarized David Elbaz, French astrophysicist: “We will discover the formation of buried stars in interstellar dust, galaxies invisible because buried in chrysalises of dust”, he was enthusiastic, moved and impatient to discover the images.
Other big differences between the two telescopes: James Webb’s main mirror is almost three times larger than Hubble’s, and it evolves much further: 1.5 million kilometers from Earth, compared to 600 kilometers for Hubble.