Home » Here are the images that astronomers have been waiting for – Marina Koren

Here are the images that astronomers have been waiting for – Marina Koren

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Here are the images that astronomers have been waiting for – Marina Koren

July 12, 2022 6:22 pm

Those bright, pointed dots are nearby stars, but each little oval, each glittering lump is a distant galaxy, a swirling creation filled with stars, dust and planets. Some of the galaxies in the foreground are part of a cluster called SMACS 0723, which is so massive that its gravity warps light from other galaxies further away. The effect increases their brightness, causing thousands to emerge from the darkness. Cosmic gems fill every corner of the frame, each immortalized as it appeared billions of years ago when the starlight left their glittering edges and began to sweep across the universe.

The image, released on July 11, was taken by the world‘s newest space observatory, the James Webb Space Telescope. This is the first true snapshot of the mission, launched more than six months ago and currently in orbit about one million kilometers from Earth.

The image is beautiful and sparkling, a great choice for a computer wallpaper. But it is also, more importantly, a completely new view of the universe. Light from galaxies in the foreground started 4.6 billion years ago, and that from galaxies in the background even earlier. All of this light was captured in unprecedented detail by the most powerful space telescope in history, making this snapshot one of the deepest, highest resolution images of the universe that humanity has ever taken.

Astronomers call this type of vision “deep field”: an image of a point in space, made with long exposure times so that the instrument can really absorb all the incoming light. Remember Hubble and that glorious deep-field image from the 1990s, with thousands of glittering galaxies? The Webb telescope was designed to detect celestial objects about one hundred times less bright than those that Hubble can detect.

The image is not the deepest that Webb is able to obtain, but the astronomers of the Webb team are nonetheless surprised by how beautiful it is, and have realized something extraordinary about the observatory’s capabilities. Virtually every image taken by the Webb telescope of a certain cosmic object will in fact be a deep field image, a snapshot from previously unattainable depths, the glittering background of distant galaxies that the telescope captured by accident. And each new image has the potential to become our deepest insight ever.

The widespread image is, on a practical level, proof of the success of the mission for NASA and its partners in this ambitious effort, the European Space Agency and the Canadian Space Agency. It’s as if space agencies could now shout publicly: Look at this ten billion dollar space telescope we’ve been working on for more than 25 years – it works! It works great.

The NGC 3132 nebula as seen by the James Webb telescope.

(NASA, ESA, CSA, STScI)

But on a deeper level (sorry) the image represents something else, a kind of cosmic leveling. We are here, on this little ball of rock in a boundless universe, and we have been able to glimpse the universe as it was billions of years before we existed. We have extended our perception of the universe from the night sky to planets, other suns and other galaxies, and we will soon catch an even older light, even further away from us, closer to the great, mysterious moment in which the universe has began.

This type of deep field science is a fairly new discipline. Before the launch of Hubble in the early 1990s, astronomy took place in the following way: you chose a star, galaxy or other cosmic object you wanted to study and point a telescope in its direction. “It never happened to take the telescope and point it at a very empty patch of sky, because it would be a waste of telescopic time,” Caitlin Casey, an astronomer at the University of Texas at Austin, told me.

That’s exactly what astronomers told Bob Williams, then director of the institution that ran the Hubble Space Telescope, when in 1995 he decided to do exactly that. Williams thought that if he pointed Hubble at a rather empty region for several hours straight, the telescope would reveal something interesting; after all, the longer a space telescope looks in one direction, the more light it detects. His intuition turned out to be correct, and the effort produced the famous Hubble deep field, a view of some three thousand galaxies that stretched billions of years back in time.

Da Hubble a Webb
Since then Hubble has produced several deep fields, reaching the limit of its capabilities. By now the telescope, which is 32 years old and observes the cosmos in the visible and ultraviolet wavelengths, with just a hint of infrared, has seen as far in time as possible. Hubble is unable to locate the farthest stars and galaxies in the universe; the glow emanating from these objects started out as visible light, but traveled through space so long that it reached Earth as infrared light. And infrared light is Webb’s specialty. Casey and other astronomers have already secured time on Webb to do what Williams did nearly thirty years ago. According to Casey, if Hubble’s deep field were contained in a sheet of paper, Webb’s equivalent would be a 16-by-16-meter mural.

Webb is not destined to observe only ancient stars and galaxies. The telescope can study almost everything from planets in our solar system to star-forming regions millions of light years away. Unlike visible light, infrared can pass through cosmic dust, which means Webb will detect objects that are invisible to Hubble. And Webb is so sensitive, Casey said, that even when he’s not looking for a distant group of galaxies, they’re bound to photobomb. “Wherever you look in the sky, even if you are looking at a planet in the solar system, you will see these galaxies in the background,” said Casey.

NASA then released other Webb images, marking the beginning of the mission’s scientific operations. Scientists are excited, eager to analyze the data behind the beautiful images. The enthusiasm of some astronomers is mitigated by the controversy over the name of Webb, a former NASA administrator who according to some was complicit in discriminating against LGBT + civil servants in the 1950s and 1960s; NASA has conducted an investigation into the administrator’s past, but has so far refused to consider renaming the mission. However, the general mood of the astronomical community is much more cheerful than in December, when Webb was still on the launch pad off the coast of South America.

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I remember sitting in the control room of the mission in French Guiana and talking to Pierre Ferruit, a Webb project scientist at the European Space Agency, who looked nervous like everyone else in the city. At the time, no one could have predicted that Webb would move so smoothly through the very complicated deployment operations planned for his first few months in space.

When I spoke to Ferruit on Zoom a few days ago, he was beaming with relief. “We feared the launch, we feared the deployment and instead everything went smoothly,” he told me. She had seen the first set of images, and they were fantastic. Now, finally, the time has come for astronomers to let go of their worries about mechanics, and focus on what the telescope is able to show us about the wonderful and mysterious universe that surrounds our little ball of rock.

(Translation by Federico Ferrone)

This article was published by Atlantic.

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