Explained: What exactly does image captured by NASA's James Webb Telescope comprise of?

The astronomers are enthralled by the release of the James Webb Space Telescope's first scientific image. During a press conference at the White House on July 11, US President Joe Biden unveiled the historic image, which is the most detailed astronomical image of the distant Universe.

On July 12, the space agency NASA is expected to release more images.

Before its release, the first image was closely guarded and demonstrates how the telescope can be transformed. It depicts thousands of distant galaxies in the constellation Volans that are fainter than any galaxies seen before in a patch of sky no larger than a grain of sand held at arm's length.

It shows the oldest documented light in the history of the Universe, from over 13 billion; let me say that again, 13 billion years ago. It’s hard to even fathom," Biden said while releasing the image.

What is NASA's James Webb Telescope?

The largest telescope to ever be launched into space, Webb, is expected to revolutionise the way that the universe is understood. The early Universe, the evolution of galaxies and stars, and extrasolar planets have all been included in the first set of images that have been made public, including the deep-field image. In contrast to one of the biggest and most well-known space telescopes, Hubble, Webb primarily detects infrared wavelengths.

It can look further into the cosmos than ever before by observing infrared light because it can get through the dust clouds that cover up young stars. The Guardian reported quoting, Zolt Levay, a retired astronomer and image processor who spent decades processing Hubble imagery, that Webb is not Hubble version 2 and it's really a very different telescope. 

What does image captured by Webb Telescope comprise of?

Because the expansion of the Universe has shifted their light out of the visible part of the electromagnetic spectrum and into the infrared, galaxies that are very far from Earth can only be seen in infrared wavelengths. This effect is prominently visible in Webb's first deep-field image near the SMACS 0723 galaxy cluster, which is about 4 billion light-years from Earth. Astronomers are able to see extremely distant objects because the gravitational pull of the clusters bends and magnifies the light of objects behind it.

"The things that are catching my eye are the distorted galaxies. They look like no other galaxies that we know of," Lisa Dang, an astronomer at McGill University in Montreal, Canada, stated, according to Nature media agency.

The first image from Webb shows galaxies that may have existed before 13 billion years ago, almost at the time of the Big Bang that gave rise to the universe 13.8 billion years ago. It is reminiscent of several iconic Hubble deep-field images. The first of those, taken over a period of 10 days over the 1995 Christmas holidays, showed that a region of the sky that appeared to be empty was actually dotted with thousands of previously undiscovered galaxies.

Webb's first image took only 12.5 hours to compile, compared to the weeks it took Hubble to observe other deep fields. Webb is an expert in spectroscopy (the study of how light interacts with matter at various wavelengths). In contrast to images, Webb's infrared spectra of astronomical objects can provide chemical composition information about the objects. That's where some of the really exciting science will take place, according to Elizabeth Kessler, a historian at Stanford University in California who has looked at how Hubble imagery affects aesthetic quality, Nature reported.

The James Webb Telescope project

The telescope project, which has been plagued by years of delays and billions of dollars in cost overruns, feels somewhat cathartic after seeing Webb's first scientific images. Webb ultimately cost NASA close to US$10 billion, despite its 1989 original conception. The observatory is the most intricate one ever constructed in space. Through a series of nerve-wracking manoeuvres, its 6.5-metre-wide primary mirror had to be folded up for launch and then spread out like a butterfly.

To ensure that the telescope's sun shield, which is the size of a tennis court and is made of layers of gossamer-thin polymer film coated with aluminium, will unfold correctly and shield the telescope's instruments from the extreme cold of space, engineers had to test it several times. The telescope was made possible by approximately another $1 billion in funding from NASA's partners, the Canadian and European space agencies.

After spending six months preparing its instruments for science, Webb finally launched in December 2021; it will continue to operate for at least 20 years. James E. Webb, who oversaw NASA at the height of the Apollo Moon exploration program in the 1960s, is the inspiration for the name Webb. 

Given that James Webb played a significant leadership role at the US State Department in the late 1940s and early 1950s, when the agency led the US government's initiative to find and dismiss gay and lesbian employees, some astronomers have called for the telescope to be renamed. According to NASA, there is insufficient evidence to support renaming the telescope. A report on their findings is anticipated to be published soon by its acting chief historian and another historian who are still investigating the matter.

What to expect in future?

The first Webb image represent only a sliver of the science that will be possible. They were captured over the course of just 120 hours of observation over the previous few weeks. Future research will focus on the planets Jupiter and Saturn, small faint stars called red dwarfs, far-off galaxies that are colliding, and hot, rocky planets that orbit other stars. On July 2, U, who has observing time on Webb, is already looking forward to receiving her first data from the telescope, according to NASA.

When that time comes, she and her coworkers will be able to access observations of galaxy mergers that the Webb team has uploaded to a website. Levay recalled contributing to the publication of some of Hubble's most famous images, such as those taken after astronauts visited the Earth-orbiting telescope to upgrade its equipment.

Image: NASA/Twitter