In 2018, when the James Webb Space Telescope (JWST) opens its enormous eye on the universe and begins collecting data, the astronomers who envisioned it and the engineers who designed and built it will celebrate and cheer.
But even as the first waves of data beam down to Earth, another team of scientists will be hard at work designing its replacement. In fact, they have already begun.
Conceiving of, researching, and building science’s biggest, most valuable tools of inquiry — the Large Hadron Collider, or the Hubble and James Webb space telescopes — requires dozens of years, hundreds of expert panels and team meetings, and billions of dollars, and the gears that march these projects through the bureaucratic assembly line turn slowly. So it should come as no surprise that, while it won’t fly until at least the mid-2030s, astronomers are already planning the next next large space observatory, currently known as the High Definition Space Telescope (HDST).
Since the moment Hubble left the launchpad, different groups have discussed what this future project might look like, but they all agree on the basic requirements and objectives. “There’s not a million ways to do it,” says Sara Seager, astronomer at the Massachusetts Institute of Technology. She was also a co-chair for the committee tasked by the Association of Universities for Research in Astronomy (AURA) to define a vision for HDST. “You have your science drivers and your engineering constraints, and you try to find a happy medium among all of those.”
So, balanced between technologies within reach and the most pressing astrophysics questions of the day, the basics are already apparent to Seager and her fellow visionaries. While JWST will focus specifically on the infrared portion of the spectrum, HDST will be a true Hubble successor, with capabilities in the infrared, optical, and ultraviolet. JWST’s 6.5-meter mirror already dwarfs Hubble’s comparatively modest 2.4 meters, but HDST will span about 12 meters, matching the largest telescopes currently on Earth. And while earthbound telescopes will have advanced to 30 meters by HDST’s era, the space telescope will, like JWST before it, fly not just in space, but at the distant L2 Lagrange point, well beyond the moon’s orbit. It will command an uninterrupted and unclouded view of the heavens, far from Earth’s atmosphere or its photobombing bulk. From this pristine vantage point, it will peer into the farthest reaches of the cosmos and hunt the holy grail of astronomy: another living Earth.
