Real revolutions are rarely instantaneous. Their world-changing effects—like those from the invention of the printing press or the discovery of radioactivity—typically take generations to play out. The debut of the James Webb Space Telescope (JWST) may mark a similarly epochal event in human history. But whether JWST’s revolution proves momentary—or instead endures and expands for many generations to come—now depends on how we choose to chase the new cosmic vistas it has only just begun to reveal.
Custom-made to find and study the very first galaxies, JWST’s unprecedentedly powerful infrared gaze is already delivering insights from across cosmic history, whether concerning the early evolution of the universe or the atmospheric chemistry of nearby exoplanets. Given its presently unparalleled capabilities—and its price tag of more than $10 billion—some might consider JWST the “one telescope to rule them all,” the greatest and last orbital observatory we’ll ever really need. But JWST alone cannot address all of astronomers’ and cosmologists’ questions. In fact, it is instead unveiling fresh mysteries, each generating additional inquiries that require a new generation of observatories — and observers — to answer. A lack of follow through on such follow-on work would effectively diminish, in the long-term, the immense economic and scientific endeavor that led to building, launching, and operating JWST in the first place. Thankfully, scientists and policymakers are attempting to plan for such things in the “post-JWST” era, at a moment when there are already exciting signs of surprising scientific results.
Some trouble lies where JWST is now breaking observational records previously thought unreachable: the distant universe, where its quarry of firstborn stars and galaxies dwell. JWST’s deepest, farthest-seeing images are revealing unexpectedly large numbers of galaxies so big and bright they defy easy understanding. Explaining how they came to be could lead to major revisions to our models of the early cosmos—and to our knowledge of the fundamental physical laws such models encapsulate.
Consider, for instance, the case of GN-z11. First glimpsed by JWST’s predecessor, the Hubble Space Telescope, this is a galaxy that is among the earliest and most distant ever seen. To date JWST has spent at least 20 hours closely studying GN-z11—a heavy investment of the telescope’s precious observing time, yet one that still leaves open whether this faraway galaxy possesses a central supermassive black hole. Such black holes, which Hubble found lurking in most large galaxies it observed closer to us in the universe, pose a “chicken and egg” problem for cosmologists: Which came first, the giant black holes, or the galaxies they occupy? Solving that mystery could reveal how the very first black holes and galaxies were born after the big bang.
Astrophysics thrives when astronomers can synergistically use multiple telescopes operating across a wide range of the electromagnetic spectrum. Time and again, this broadband view has been essential for learning the true nature of mysterious objects in the heavens. To gain a better picture of the population of black holes in the universe, what’s needed now are x-ray observations. Although not as sublime as their optical counterparts, x-ray images reveal the most extreme cosmic events—such as a supermassive black hole feasting on galactic volumes of gas and dust—which emit lots of energetic x-rays. Detecting even a few stray x-ray photons from GN-z11 or one of its kin would strongly suggest the presence of a supermassive black hole there, providing invaluable data points for the timing and mechanics of cosmic evolution.
But no facility yet exists to perform these demanding observations. The current major x-ray telescopes, Chandra and XMM-Newton, have both significantly degraded since being launched more than 20 years ago, and neither is sensitive enough to detect black holes smaller than about one million solar masses in the remote cosmic regions that JWST is exploring. Without a more powerful state-of-the-art x-ray observatory, we may miss our chance to understand how black holes evolved in space and time—an enigma revealed by successive generations of humankind’s best, most cherished space telescopes.
This helps explain why many astronomers are now already looking beyond JWST and its forecast 20-year lifetime to envision an ambitious series of “New Great Observatories,” each sensitive to a different type of light. Ideally, all would have to be launched in relatively rapid succession around the time JWST’s mission ends, maximizing scientific return via their overlapping operational timeframes. The original Great Observatories program debuted in 1990 with NASA’s launch of Hubble and included Chandra and two additional now-defunct space telescopes, the last of which was sent to orbit in 2003.
As recommended in 2021 by the congressionally mandated Decadal Survey of U.S. astronomers, this plan calls for a trio of new space observatories. The first, now named the Habitable Worlds Observatory, would launch in the early 2040s to study potentially Earth-like exoplanets (and much, much more) in optical, ultraviolet and infrared light. The other two—one for x-rays, another for far-infrared—could launch later that decade or in the 2050s. Together, they could create a profoundly informative, more colorful view of the universe, ushering in a new golden age of space-based astronomy about half a century after Hubble’s launch. The proposed x-ray observatory, for example, could detect growing black holes as small as 10 thousand solar masses within the mysterious early galaxies seen by JWST—a factor-of-100 improvement over Chandra’s capabilities.
However, whether through wavering political support, unanticipated technological challenges or merely the harsh realities of NASA’s overloaded portfolio, there is a good chance these decadal plans will not proceed at their optimal speed. A slower pace of development and funding could result in longer lag times between launches for the three New Great Observatories, reducing the likelihood that they will operate concurrently, as well as their overall scientific return. According to one analysis, having all three facilities operational by 2045 would require doubling NASA’s Astrophysics budget through the remainder of the 2020s and into the 2030s. Currently, there’s as much evidence for such an increase becoming a reality as there are x-ray photons from these faraway galaxies—none. Far from doubling down on funds, the administration’s latest budget proposes an increase in spending of only 3 percent for NASA’s astrophysics division in the 2024 fiscal year.
With its successive multibillion-dollar investments in JWST, Hubble and their telescopic kin, the U.S. and its international partners sparked an ongoing scientific revolution representing humankind’s best hope of learning our deepest origins, context and fate. Fulfilling that profound potential and maintaining leadership in space science demands strong, sustained support for the next generation of observatories. Otherwise, we may fail to fully answer not only the current set of open questions, but any new ones that arise in our epochal quest for cosmic understanding.
This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.