The James Webb Space Telescope, the largest and most sophisticated space observatory ever built, has been sending back images and data for almost a full year now—and in that time it has delivered a treasure trove of information about everything from stars and planetary systems in our own galactic neighborhood to distant galaxies that formed when the universe was a tiny fraction of its current age. Webb has also sent back stunning images that surpass those garnered by its famous predecessor, the Hubble Space Telescope.
Webb and Hubble are quite different instruments. For starters, while Hubble is primarily sensitive to visible light, Webb records infrared light that’s invisible to the unaided eye. These longer wavelengths of light pass through clouds of gas and dust that block visible light, letting the telescope peer past such obstacles. It also has a size advantage: While Hubble’s main mirror is 8 feet across, Webb employs an array of 18 small hexagonal mirrors that function like a single mirror 21 feet across.
“Every day I’m blown away by the technological achievement that this observatory represents,” says Sasha Hinkley, an astronomer at the University of Exeter in England. “It’s really due to the thousands of scientists and engineers that have been working on it for 20 years. When I see one of these amazing images, I always stop to think about the hundreds of men and women that made this happen.”
The $10 billion observatory, built by NASA together with the Canadian Space Agency and the European Space Agency, was launched on December 25, 2021, and its first images were made public on July 11 of last year. Since then, Webb has yielded many more illuminating images, and we’ve picked our favorites and detailed their importance below.
An iconic image gets an update
You’ve almost certainly seen the iconic Hubble Space Telescope image dubbed “The Pillars of Creation.” It shows billowing clouds of dark gas—part of the Eagle Nebula—against a bright, colorful background, with hundreds of stars twinkling in front of and behind the structure. But as stunning as the Hubble image was, Webb has revealed even more of this scene. For starters, it has brought into view the young red stars that are sprinkled throughout the nebulous clouds. Astronomers call them “protostars,” because they’re not yet massive enough and hot enough to burn hydrogen in their cores.
These young stars were obscured behind the dust and gas in the original Hubble image, explains Anton Koekemoer, an astronomer at the Space Telescope Science Institute in Baltimore. “Because these clouds are so dense and full of dust, when Hubble looked at them it only saw their outer surface,” he says. “We couldn’t really look inside them.”
Now, thanks to the dust-penetrating power of Webb, astronomers can glimpse these star-forming regions deep inside the nebula, which is located some 7,000 light-years from Earth. Koekemoer describes it as a “laboratory” for studying star formation. With Webb, “we can now begin to see, in great detail, these dense regions of gas and dust, and how new stars are forming, inside these ‘pillars.’”
Capturing an exoplanet
By now, astronomers have inferred the existence of thousands of exoplanets—planets orbiting stars beyond our own solar system. But actually photographing these distant worlds is a challenge—primarily because their dim light is overwhelmed by the light of their host star. Nonetheless, the new telescope has pulled it off, imaging a planet called HIP 65426 b using an instrument called a coronagraph that blocks out the light from the star.
HIP 65426 b is believed to be a gas giant planet, a half-dozen times the size of Jupiter; it orbits its host star at a distance about 100 times greater than the Earth-sun distance. With no solid surface, the exoplanet is unlikely to be habitable, but merely being able to photograph it is an accomplishment.
“These first observations are showing us that JWST is even more sensitive than we had hoped for,” says Hinkley. “Its performance is better than we expected. Which means we can now be really ambitious and search for exoplanets that had been out of reach with other instruments.”
Probing a planetary atmosphere
One of Webb’s most remarkable achievements is its ability to garner information about the atmospheres of planets orbiting stars hundreds of light-years from Earth. One of those is a gas giant planet dubbed WASP-39 b, which is roughly as massive as Saturn but revolves around its host star in a much tighter orbit than Mercury’s orbit around the sun.
Astronomers used instruments on board Webb to record the spectrum of the planet’s atmosphere, which in turn provides clues as to what chemicals are found there. And they’ve turned up a whole slew of atomic and molecular gases, including water vapor, sulfur dioxide, carbon monoxide, sodium and potassium.
“The real surprise was sulfur dioxide,” says Laura Flagg, a postdoctoral research associate at Cornell University. The planet is so hot, the processes that normally lead to the creation of sulfur dioxide shouldn’t be happening—which means that less common reactions, like photochemistry, are likely responsible. A photochemical reaction is triggered when intense light hits certain compounds—in this case, light from the host star hitting water molecules in the planet’s atmosphere.
Getting such a detailed look at the chemistry of this exoplanet is “a big step forward,” says Flagg. “The precision we’re seeing isn’t like anything we’ve had before.”
Spectacular details of “Cosmic Cliffs” emerge
One of the most striking images to come from Webb so far is the so-called “Cosmic Cliffs,” a cloud of gas and dust in the Carina Nebula, located about 7,500 light-years from Earth. The region got its nickname because the gaseous “cliffs” seem to resemble a mountain range, though the structures are actually dust clouds being eroded by blasts of ultraviolet light from newly formed stars. What looks like steam rising from the celestial “mountains” is actually ionized gas and hot dust being blown by the radiation.
What if you could hear Webb data?— NASA Webb Telescope (@NASAWebb) August 31, 2022
Here, the “Cosmic Cliffs” are sonified, or translated to sound. Blue gas and dust sound windy, while a melodic line represents the rise and fall of the “mountain range.” Louder tones represent brighter light. More: https://t.co/yeOM4bUjoh pic.twitter.com/qr9WzWVWvN
As with many of Webb’s targets, this nebular region was previously known to astronomers, but it takes on a whole new appearance thanks to the observatory’s ability to see in the infrared, allowing it to penetrate clouds of dust that would have stymied the Hubble Space Telescope as well as ground-based telescopes.
A family of galaxies interact
One of Webb’s first images was of a tightly clustered group of galaxies known as Stephan’s Quintet. Four of the five galaxies in the image are interacting with each other gravitationally; the fifth is actually in the foreground and merely appears to be a part of the group.
Clusters like Stephan’s Quintet offer a chance to study how galaxies interact and sometimes merge. Physicists believe galaxy mergers would have been common in the early universe and that such mergers were one of the principal ways in which large galaxies, like those we observe today, came into existence. These inter-galaxy interactions can also trigger star formation and the formation of black holes. The galaxy known as NGC 7319 (the uppermost galaxy in the image) is believed to harbor a supermassive black hole with a mass some 24 million times that of the sun.
A star’s strange ripples tell of stellar wind blasts
One of Webb’s more unusual images is the one it snapped of a star known as WR 140. The Wolf-Rayet star, as it’s classified, is a type of unusually hot star with ionized helium, nitrogen and carbon in its atmosphere. But what’s striking about WR 140 is the series of not-quite-circular concentric rings that surround it. While the effect might be mistaken for an artifact of the way the image was produced, astronomers say that in this case the rings are quite real.
Researchers believe the rings are shells of material surrounding the star, which is actually a double star system. Whenever the two stars are closest to one another, which happens every eight years, they emit an increased amount of “stellar wind,” or streams of charged particles that push against whatever gas and dust are in the neighborhood. The even spacing between the shells suggests they’re being created at regular intervals. Astronomers are able to count 17 of these shells, which bear witness to 130 years of dust formation.
Revealing the depths of space
In 1995, the Hubble Space Telescope was aimed at a nondescript patch of sky while its cameras recorded ten days’ worth of data. The resulting image, known as the Hubble Deep Field, revealed some 3,000 previously unknown objects, most of them distant galaxies.
Last summer, Webb repeated that feat—and it became the telescope’s first publicly released image, unveiled by U.S. President Joe Biden last July. But the new image was produced much more speedily than Hubble’s. “This image from Webb took about 12 hours—a tiny fraction of the time needed for the Hubble image,” says Sarah Kendrew, a European Space Agency astronomer based at the Space Telescope Science Institute.
The first image from the Webb Space Telescope represents a historic moment for science and technology. For astronomy and space exploration.— President Biden (@POTUS) July 11, 2022
And for America and all humanity. pic.twitter.com/cI2UUQcQXj
A cluster of galaxies known as SMACS 0723, located nearly 5 billion light-years from Earth, dominates the image. But the combined mass of this galaxy cluster acts as a “gravitational lens,” giving a magnified view of more distant galaxies in the background. The lensing effect also creates dozens of curved arcs of light, which can be seen in the picture. The image, says Kendrew, “was really a sign of what was to come from this observatory.”