Astronomers working with the James Webb Space Telescope have taken a very deep dive into the cosmos, offering a historic debut image of distant galaxies that reaches back like a time tunnel across much of the universe’s 13.8-billion-year history.
The photo marks a milestone for the newly commissioned telescope, the most powerful ever to fly in space. Both visually compelling and scientifically revealing, it demonstrates that Webb is performing at the level required to fulfill its scientific mission.
Declaring the telescope “miraculous,” United States President Joe Biden unveiled the image during a White House briefing on Monday. It is just the first taste of the telescope’s capabilities, with more photos to follow on Tuesday morning.
Monday’s photo shows a remote but massive cluster of galaxies known only by the catalogue designation SMACS J0723.3-7327 and located some five billion light years away. It includes a series of slender arcs centred around the cluster. The arcs are images of other galaxies, many billions of light years farther in the background, which have been stretched and magnified by the gravity of the central cluster.
The phenomenon known as “gravitational lensing” is one that astronomers have said they plan to use to extend Webb’s penetrating gaze and use it to probe cosmic history. Because of the time required for light to travel across space, the most distant objects in the image appear not as they are now but as they once were when the universe was a small fraction of its present age.
“We’re going back almost to the beginning,” NASA’s chief administrator, Bill Nelson, said after the unveiling.
While the image is superficially similar to the view that its predecessor, the still-active Hubble Space Telescope, has provided of the same target, it includes a wealth of detail that is markedly different. The overall effect makes the image appear more crowded than a Hubble photo because of Webb’s superior light gathering power.
“This is truly spectacular,” said Anton Koekemoer, a research astrophysicist at the Space Telescope Science Institute in Baltimore who was involved in preparing Webb’s initial round of images. “It’s one thing to know what to expect based on the telescope’s specifications, but it’s another to actually see the images come down and have them in front of you.”
The galaxy cluster is one of five celestial objects chosen by the telescope’s science team to demonstrate Webb’s capabilities. Last week, NASA revealed that additional images will include: the Carina Nebula, a vast star-forming region in the Milky Way; the Southern Ring Nebula, a bubble of hot gas expelled by a dying star; and an iconic group of galaxies called Stephan’s Quintet, four of which are locked in an elaborate gravitational dance.
Looking closer to home, astronomers will also release the spectrum of a planet called WASP-96 b, spotted as it crossed in front of the star it orbits. The observation will reveal details about the giant planet’s atmosphere.
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Canada is a partner in the new space telescope, which was primarily built and paid for by the U.S. and launched aboard a French Ariane rocket late last year. Since then, mission scientists have been putting Webb through its paces. The elaborate startup process included using a Canadian-built instrument called the Fine Guidance Sensor to align the telescope’s 18 gold-plated mirror segments and create a seamless reflecting surface 6.5 metres across.
After enduring technical hurdles, budget cuts and years of delay on the road to the launch pad, astronomers involved with the project are now revelling in the performance that Webb is demonstrating with its initial release.
René Doyon, a professor of astronomy at the University of Montreal and principal investigator with the Canadian Webb science team, said that in spite of his high expectations, he was still astonished at the quality of data the telescope and its five science instruments are delivering, and the speed at which the giant telescope can gather up light from distance sources.
“It’s such a sensitive instrument,” said Dr. Doyon, who will use the telescope to investigate the atmospheres of planets beyond our solar system. He added that there’s no question that the telescope will deliver on its scientific promise and that several of its instruments, including Canada’s Near Infrared Imager and Slitless Spectrograph, are surpassing their design specifications.
But in selecting the first image for release, astronomers have chosen to highlight the telescope’s unprecedented potential as a probe of the early universe.
Chris Willott, a senior scientist at the Herzberg Astronomy and Astrophysics Research Centre in Victoria who will work with the Webb data to discern clues about the origins of galaxies, said that he and his team were mesmerized when Monday’s photo was presented.
“Everyone gathered around the screen to take a closer look,” Dr. Willott said. “There were gasps as we panned around the image and looked in detail at several galaxies.”
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