In its first year JWST proves its worth

In its first year JWST proves its worth

NASA has a tradition of naming space telescopes after astronomers who lived so long ago that the concept of space telescopes was, at best, on the far fringes of science fiction. The Hubble Space Telescope, for example, commemorates Edwin Hubble, born in 1889—eight years before H.G. Wells even conceived of his classic novel War of the Worlds. The Kepler Space Telescope was named for Johannas Kepler, born all the way back in 1571.

So, most of us can be excused if we don’t recognize the namesake for the James Webb Space Telescope (JWST), NASA’s latest, greatest, and (with a $US10 billion price tag) most expensive to date.

Webb’s claim to fame is that he was in charge of NASA’s Moon landing program until he retired, shortly before it culminated in Neil Armstrong’s giant leap for mankind. The telescope named for him may well exceed his own legacy. Even though it has only been on station, 1.5 million kilometers from Earth, for 21 months, it is already redefining our understanding of everything from our own Solar System to the Universe as a whole.

To most of us, space telescopes are merely a source of pretty pictures—the type of thing that can be made into posters to grace the bedroom walls of future scientists.

No matter where it is pointed, what you see are galaxies upon galaxies upon galaxies.

But it takes only one look at the new images to see one of the JWST’s greatest impacts. No matter where it is pointed, what you see are galaxies upon galaxies upon galaxies.

Our own galaxy has 100 billion stars. JWST is showing perhaps 2 trillion galaxies in the observable Universe—20 for every star in the Milky Way. Deep-space images from the JWST don’t show fields of stars with a few galaxies in the background. They show fields of galaxies with occasional stars in the foreground.

It’s a radical restructuring of our place in the Universe. “When I think back to when I was a graduate student and we could barely detect a nearby galaxy, this is like ‘whoa,’” said Marcia Rieke, an astronomer at the University of Arizona who is principal investigator on one of Hubble’s cameras, last month at a conference on the first year of the JWST’s full-scale operations.  

52212143385 3f187b9b3b k 850
Webb’s First Deep Field is galaxy cluster SMACS 0723, and it is teeming with thousands of galaxies – including the faintest objects ever observed in the infrared. Credit: NASA, ESA, CSA, and STScI

From these images, scientists are peering back farther and farther toward the dawn of the Universe, trying to figure out when the first galaxies formed and how they evolved.

“One of the James Webb’s chief science goals [was] first light,” says James Chester of the University of Manchester, UK—by which he means the light from the Universe’s earliest galaxies, traveling toward us for much of the age of the Universe (currently estimated at 13.8 billion years).

Scientists are peering back farther and farther toward the dawn of the Universe.

The previous record belonged to the Hubble Space Telescope, which has managed to spot galaxies formed well within the first billion years after the Big Bang. But JWST quickly upstaged it with a galaxy called JADES-GS-z13-0.

“JADES-GS-z13-0 has been confirmed with two different techniques to be [from] only 400 million years after the Big Bang,” NASA scientist Stefanie Milam said on 4 October at a meeting of the American Astronomical Society’s Division for Planetary Sciences in San Antonio, Texas. “This blows away Hubble’s previous record.”

Furthermore, says Mauro Stefanon of Leiden University, The Netherlands, some of the early galaxies JWST is finding are very bright and probably very massive—something astrophysicists didn’t think was possible that early in the Universe’s history.

One might think that this type of challenge to their pet theories might create tensions between theoretical astrophysicists and observational astronomers. But actually, it’s the type of thing that keeps both excited. One group makes predictions. The other looks for data that either confirms these predictions or sends them back to the drawing board. It’s not a competition. It’s a symbiotic dance in which both hope to spiral ever closer to the truth, making it a field in which surprises are cherished.

Stsci 01gnymeg4ym0ksh1x63g894t6h 850
NGC 346, shown here in this image from NASA’s James Webb Space Telescope Near-Infrared Camera (NIRCam), is a dynamic star cluster that lies within a nebula 200,000 light years away. NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way. Credit: NASA, ESA, CSA, O. Jones (UK ATC), G. De Marchi (ESTEC), and M. Meixner (USRA). Image processing: A. Pagan (STScI), N. Habel (USRA), L. Lenkic (USRA) and L. Chu (NASA/Ames)

Distant galaxies aren’t JWST’s only target. It has also turned its attention to star-forming regions in our own galaxy and the nearby Small Magellanic Cloud, examining them in unpreceded detail. “You see all this fantastic structure,” Milam says—scientist-speak for this might be the next poster you want on your bedroom wall.

Closer yet, JWST has peered at unprecedented depth into protoplanetary disks surrounding newly forming stars, observing, in real time, not only how solar systems form, but how giant planets, like our own solar system’s Jupiter, might produce their moons.

Another major target is exoplanets, of which more than 5,500 are now known.

Prior telescopes, most notably Kepler, detected their existence by the degree to which they dimmed their sun’s light as they passed between it and us. But that’s passé. JWST allows scientists to examine tiny details in the spectrum of the light as the planet moves across its sun, looking for the chemical signatures of important gases in the planet’s atmosphere.

Could this eventually reveal signs of an extraterrestrial civilization? Who knows. At the moment the dream is simply to find an earthlike world that might have life of one kind or another.

A graphic titled “exoplanet k2-18 b: atmosphere composition. ” the graphic shows the spectra of the exoplanet k2-18 b from niriss and nirspec in the form of a graph, with the vertical y-axis labeled as amount of light blocked and the horizontal axis labeled as wavelength of light (microns). The data is plotted as dots with vertical error bars. A jagged blue line running through the plot represents the best-fit model. There are semi-transparent magenta, red and green vertical columns also scattered across the plot, indicating where variations in the line represent the presence of methane, carbon dioxide, and dimethyl sulfide combined with other molecules, respectively. Behind the graph is an illustration of the planet and star. The planet is a large fuzzy blue-ish sphere off to the right, taking up half of the background. The red star is smaller at the bottom left of the entire graphic.
Atmosphere composition of Exoplanet K2-18 b (NIRISS & NIRSpec) detected by the James Webb Space Telescope. Credit: NASA, ESA, CSA, Ralf Crawford (STScI), Joseph Olmsted (STScI). Science: Nikku Madhusudhan (IoA)

Closer in, JWST scientists are looking at objects in our own Solar System. Some are comets, for which, Milam says, JWST has been able to get spectroscopic data good enough to match anything possible without actually sending a spacecraft out to take a closer look. “We can get flyby-quality imaging at wavelengths we don’t have access to from the ground [due to interference from the Earth’s atmosphere,]” she says.

The same works for planets like Jupiter, Saturn, Uranus, and Neptune, the latter two of which haven’t been seen close-up since the Voyager missions of the 1980s.

“It has been almost like a new grand tour of the outer Solar System,” says Leigh Fletcher of the University of Leicester, UK, in a reference to the Voyager program. The key, he adds, isn’t just JWST’s ability to take high-resolution pictures, but the fact that each pixel contains detailed spectroscopic data over a wide range of wavelengths.

That allows scientists not just to see gases that had never been observed before, but to peer beneath the cloudtops and try to figure out what’s going on lower down. In the case of Saturn, for example, Fletcher says that for some types of data, “in just five hours of observations, we can reproduce and in many cases match, the observations that [the] Cassini [spacecraft] took 13 years to accomplish.” In the case of Jupiter, it might allow them to figure out why its Great Red Spot is red and not some other color.

Could this eventually reveal signs of an extraterrestrial civilization? Who knows.

Meanwhile, says Jane Rigby, NASA’s senior project scientist on the JWST, the telescope is in good shape, with maneuvering fuel for 20 years and optics and detectors delivering images twice as good as expected.

The only significant problem, she says, are micrometeorites striking its 6.5-meter mirror, degrading its optics. So far, she says, there have been 52 such strikes, all but one of which have had no significant effect. The 52nd, however, was a big deal. Nine more like it would be enough to put the telescope out of commission.

To some extent, being hit by a larger-than-average micrometeorite is simply bad luck. But there are things that can be done to reduce the potential damage, and one of these, Rigby says, is to, whenever possible, make sure the telescope is observing things in the opposite direction from which it is orbiting the Sun. “When you have a choice for several observational targets, you can observe them when the telescope is moving toward the target or you can do it six months later when the telescope is moving away from the target,” she says.

It’s kind of like deciding that if you are trapped in a windy rainstorm, it might be better to put your back to it, rather than facing it head-on. If it works, the JWST will be returning dorm-poster images to inspire not just today’s generation of budding scientists, but the one to come.

Please login to favourite this article.