Why the first images from the Webb telescope mean so much to scientists

Stefan’s Quintet, a visual collection of five distant galaxies, was one of the first full-color images from the Webb Telescope (NASA)

The first full-color images from the James Webb Space Telescope released Tuesday did not disappoint, as the now-operational telescope returned images of bright nebulae, dancing galaxies and the most distant star systems with resolution never seen before.

Scientists were just as amazed as the general public.

“My reaction was very unprofessional,” said Jacob Bean, an astronomer who studies exoplanets at the University of Chicago, in an interview with the independent. “Just overwhelmed and amazed at the level of detail, the richness of detail that you saw in these images.”

But the images weren’t just about communicating the sublime.

Although the five images released Tuesday were relatively quick exposures designed to show the world what Webb can do, they nonetheless provided scientifically useful information that whetted the astronomical community’s appetite for more rigorous observations. Information contained in a light spectrum from the atmosphere of exoplanet Wasp-96b already has Dr. Bean salivating over what Webb will do in his field of study.

“It’s really going to open up this field of exoplanet atmospheres,” he said.

Although US President Joe Biden previewed one of Webb’s images on Monday night, NASA presented the full set of the first five public Webb observations during a live webcast. on Tuesday morning. These included Webb’s first deep-field image, the deepest image of the universe yet taken, images of the bright Carina and Southern Ring nebulae, a collection of distant galaxies locked in a tight gravitational dance known as Stephan’s Quintet, and the Wasp- 96b. spectrum.

All of the observations highlight aspects of Webb’s mission, which includes studying the evolution of early galaxies, how stars and planets form, as well as studying other planets and looking for signs of life on them.

The deep-field image of Webb would not have been possible without a telescope in space as large as Webb, which has a primary mirror 6.5 meters in diameter compared to the Hubble Space Telescope’s 2.4-meter mirror.

To create the image, Webb pointed his huge mirror at a small patch of dark space about the size of a grain of sand held at arm’s length and took a 12.5-hour exposure. The resulting image of thousands of gem-bright galaxies reveals some that are 13.1 billion light-years away, and since a light-year is the distance light travels in one year, 13 billion years.

Webb's first deep field image shows galaxies up to 13.1 billion light-years away (NASA)

Webb’s first deep field image shows galaxies up to 13.1 billion light-years away (NASA)

“Very red objects tell you that these are very distant galaxies,” said Dr Bean. “Anything red in that kind of image tells you that it’s quite old, that it’s very distant.”

That’s because light from the most distant objects in the universe has been stretched out over time, those light waves stretched out by the expansion of the universe itself over billions of years. As the wavelength of light grew longer, it shifted out of the range of visible light into the infrared end of the spectrum: Webb is a purely infrared telescope and exquisitely sensitive for precisely this reason.

However, even finely tuned instruments and Webb’s huge mirror were unable to resolve the more distant galaxies seen in the deep-field image unaided.

Looking closely at the image, you can see some distortion in the shapes of the galaxies around the center. That’s because Webb focused on SMACS 0723, a galaxy cluster closest to Earth just over 4 billion light-years away.

The gravity of the massive galaxy cluster acts like a lens, bending and magnifying the light from the much more distant galaxies behind the cluster. Using this technique, known as gravitational lensing, scientists will soon use Webb to look much further back in time. Ideally, look back up to 200 million years after the Big Bang to capture the formation of the first galaxies in the Cosmos.

The Carina Nebula is a vast cloud of gas, dust, and a nursery of newborn stars located about 7,600 light-years from Earth in the southern constellation of Carina. Webb’s image of the Carina Nebula focuses on a part of the larger nebula known as NGC 3324, or the “cosmic cliffs” because of its resemblance to a mountainous horizon. However, the tallest of the imaged peaks is seven light-years across. That’s longer than the distance between Earth and the nearest star, Proxima Centauri.

Webb's image of the Carina Nebula reveals newborn stars (Nasa)

Webb’s image of the Carina Nebula reveals newborn stars (Nasa)

Webb’s image of Carina was created by merging data taken with the telescope’s Near Infrared Camera (NIRCam) and Mid-Infrared Instrument (Miri), which revealed aspects of the nebula hidden in previous Hubble observations. Miri’s addition reveals young stars with planet-forming disks that appear pink or reddish in color, along with outflowing jets of gas.

Unlike Carina, the South Ring Nebula is not a stellar nursery, but rather a stellar nursing home, the glowing layers of gas and dust expelled by a dying star at the center of the planetary nebula. Located about 2,500 light-years from Earth, Webb observed the nebula with his two NIRCam Miri instruments, each revealing different details.

Webb captured images of the South Ring Nebula in near-infrared (left) and mid-infrared (right) light.  (NASA, ESA, CSA, STScI and The E)

Webb captured images of the South Ring Nebula in near-infrared (left) and mid-infrared (right) light. (NASA, ESA, CSA, STScI and The E)

The NIRCam images highlight the nebula’s bright stars and complex layers of gas, while the Miri image makes it clear that there are two stars orbiting each other in the nebula’s center. The fainter star is on its deathbed and is the source of the nebula’s gas, while the brighter star is younger, although it will eventually share the fate of the older star and contribute its own gas to the nebula.

The gas and dust released by planetary nebulae may eventually become part of other stars or their planets.

Stephan’s Quintet is a grouping of five galaxies as seen from Earth. Only four of the galaxies are relatively close to each other, about 290 million light-years from Earth, with the fifth foreground galaxy located just 40 million light-years away. A much less detailed image of the quintet of galaxies appeared in the American Christmas movie starring Jimmy Stewart, “It’s a wonderful life.”

Webb’s image, the telescope’s largest to date and made up of 1,000 separate image files, documents how gravity from four nearby interacting galaxies generates shock waves and pulls stars and gas from each other. Webb’s instruments also revealed material ejected from the supermassive black hole at the center of a galaxy, an actively feeding black hole emitting energy equivalent to 40 billion suns.

“These large image mosaics of galaxies and nebulae reveal so much fine detail that I think they will really tell us about the physics of these objects,” Dr Bean said. the independent“to understand what’s driving what we’re seeing there.”

However, the Webb image that most excited Dr. Bean was not a large nebula or a distant galaxy, but the spectrum of the exoplanet Wasp-96b, the pattern generated by observing starlight filtering through the atmosphere of the planet. planet. Because different molecules absorb different wavelengths of light, a spectrum can tell scientists about the chemical composition of distant objects.

Webb's spectrum for exoplanet Wasp-96b, the most detailed exoplanet spectrum yet, shows multiple water vapor features (Nasa)

Webb’s spectrum for exoplanet Wasp-96b, the most detailed exoplanet spectrum yet, shows multiple water vapor features (Nasa)

“The special thing about that spectrum is that you see, very clearly with the naked eye, the bumps and ripples in the spectrum that are due to water vapor,” said Dr. Bean. Hubble and other instruments have detected water vapor in exoplanet spectra before, but “there’s a lot more information there, there are more subtle bumps and ripples that could be due to other chemical species.”

It’s the most detailed spectrum of an exoplanet ever collected, Dr. Bean added, and it was collected much more casually than upcoming exoplanet spectra taken as part of scientific investigations.

We’ll refine those spectra. We are going to do this for many other planets. We are going to expand the wavelength range, so we can see many more chemical species beyond water,” he said. “In the long run, maybe we can look for signs of life in the atmospheres of exoplanets, all using this kind of technique that was used to produce a spectrum of Wasp-96b.”

Dr. Bean has studied exoplanets for more than a decade in anticipation of the day Webb would finally start looking into space. He is excited to be part of a large group that is already studying the spectrum of Wasp-96b. But as exciting as the technical achievements leading up to this moment may be, and the moments of scientific discovery to come, he believes Webb can inspire people to something more universal.

“I think it means something pretty important beyond science, which is what we can achieve when people find common ground and work together,” said Dr. Bean, noting that Webb is a collaboration between thousands of people, scientists , engineers and program managers, all over the world. United States, Canada and the European Space Agency.

“Look at what we can achieve when we find that common ground and work together, these beautiful images from outer space, a deeper understanding of our universe that we live in.”

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