Among astronomers, it’s a commonplace that the last few decades have been a golden age. Starting around 50 years ago, astronomy found itself on a winning streak of truly amazing discoveries. But are the good times about to stop rolling? No golden age lasts forever, and there’s reason to fear that astronomy is ending its long run of wonders.
Why do I worry? Our early successes came from looking through new windows across a vast range of wavelengths invisible to the naked eye. The first radio, X-ray, ultraviolet and infrared telescopes were small, but everything we saw through them was new and mysterious. The next generation of telescopes leaped forward in capabilities, leading to the discoveries of neutron stars, black holes, radiation left over from the big bang, dark matter, dark energy, dark energy, exoplanets … the list goes on.
But this greater power came at a cost—literally, since each new generation of telescopes carried a price tag several times higher than that of the one before. Today, a single telescope can now take almost a full decade’s worth of NASA’s budget for “Big Astronomy.” The James Webb Space Telescope (JWST), now scheduled for launch next year, takes the prize at about $8 billion.
The glory of our golden age has been that we can access the whole electromagnetic spectrum at the same time. The discovery of gravitational waves from the merger of two neutron stars is a perfect example: ground-based detectors spotted these ripples in spacetime, but follow-up observations with gamma-ray, X-ray and visible-light telescopes gave us a far more complete understanding of how the event unfolded. Ideally, we need several comparably sensitive “flagship” telescopes, on a par with JWST, and they need to be flying at the same time.
Yet such flagships are only designed to last about five years (although that can often be stretched to 10). When the infrared-sensitive JWST flies, it will be 10 to 100 times more powerful than its predecessors, the Hubble and Spitzer space telescopes. But if new flagships cost as much as JWST, it will be a decade before even one can be launched. By that time JWST itself will likely be on its last legs. So every discovery made by the Webb telescope will take over a decade to follow up. By then, we’ll have forgotten what it was that we wanted to know in the first place. Advances in astronomy will slow to a snail’s pace.
How we respond to the crisis will make all the difference. The danger is that we go on with business as usual, and simply accept this diminution of our exciting field. But we don’t have to do that. There are two positive ways to respond.
First don’t succumb to the “too big to fail” complex. The priorities for the next decade of astronomy will be set in 2020. If precedent is followed, a “decadal survey,” or authoritative report produced by committee, will rank the top science questions, and the top telescopes to answer them. We have tended to seize on the One Top Telescope and pursue it at all costs. Under this regime, JWST’s price tag ballooned from a few billion dollars to $8 billion, crowding out nearly everything else. Just why will be debated for a long time. One reason, surely, was that cancelling JWST would have left a threadbare astronomy program. Without an alternative, the only response to technical problems was to throw more money at them.
To escape this trap, the new program from the “Astro2020” survey should require multiple new missions. There are at least a half dozen ideas for much cheaper telescopes, each one dramatically better than its predecessor. They include everything from gamma-ray telescopes that can detect merging neutron stars; to X-ray and ultraviolet telescopes for probing intergalactic space and more; to a far-infrared telescope to understand how stars and planets form. The whole set are affordable within a decade.
The downside is that highly desirable, but too expensive, flagships must be postponed until the second positive response to the crisis kicks in: the leveraging of new developments in commercial space. SpaceX launches satellites at one third the traditional cost, and soon, maybe, as little as one fifth. That’s a sizable saving by itself. But it also takes the pressure off engineers to shave mass relentlessly from the telescopes themselves by using the lightest possible components. Without such a restriction, costs could plausibly be cut by two thirds. Shrinking costs makes a doubling of flagship launch rates plausible. As this commercial revolution continues, an even higher rate of flagship missions could come about.
If we embrace both of these responses we can keep the good times rolling in astronomy.