The world’s biggest digital camera is finally coming into focus. While a very powerful personal camera might have megapixel resolution, astronomers have constructed a device that will image the distant universe with 3.2 gigapixel resolution. (A gigapixel is equivalent to 1,000 megapixels.)
That camera will be the workhorse for the Vera C. Rubin Observatory’s telescope, which has been in the works for about two decades but is nearly complete. At the end of September, scientists and technicians working in an enormous clean room at the SLAC National Accelerator Laboratory in Menlo Park, California, finished assembling the sensitive camera’s mechanical components, and they are now moving ahead to its final pre-installation tests.
“In the combination of the camera’s giant focal plane and a 25-foot mirror to collect light, we are unparalleled,” says Aaron Roodman, an astrophysicist at SLAC and deputy director of the Rubin Observatory. He mentions that both the 5.5-foot lens, which comes with its own extra-large lens cap, and the focal plane are in the Guinness Book of World Records because of their extraordinary size.
Engineers will test the camera in about two months, and in May the team will put it on a chartered flight to the telescope’s site in the desert mountains of northern Chile. Scientists will conduct the telescope’s first imaging tests in the second half of 2023, and they’re aiming for Rubin’s official debut, called “first light,” in March 2024.
That’s when the telescope will begin collecting 20 terabytes of data every night for 10 years. With it, scientists will build a vast map of the sky as seen from the southern hemisphere, including 20 billion galaxies and 17 billion stars in the Milky Way—a significant fraction of all galaxies in the universe and of all stars in our own galaxy, Roodman says. They’ll also amass images of 6 million asteroids and other objects in our solar system. Such a gigantic cosmic database would’ve been unthinkable until very recently.
It’s the opposite of the approach used for the Hubble or James Webb space telescopes, which zoom in to capture spectacular images of narrow slices of the heavens. Instead, Rubin will repeatedly scan the entire southern sky—about 18,000 square degrees—collecting data on every viewable object and imaging each area 825 times at a range of optical wavelengths. Rubin will also go deeper and chart more of the cosmos than its predecessors, like the Sloan Digital Sky Survey and Dark Energy Survey.
That fire hose of valuable data will come thanks to this new, nearly 3-ton camera. Its imaging sensor is made up of more than 200 custom-designed charge-coupled devices (CCDs), and they’ll take images with six filters covering the optical electromagnetic spectrum, from violet to the edge of infrared.
The camera will image each piece of the sky every three days, providing snapshots that can be used together to examine faint or distant objects, or spot changing ones, such as supernova explosions and the paths of near-Earth asteroids and comets slowly moving in their orbits. “It’s making a 10-year color movie,” says Risa Wechsler, a Stanford University astrophysicist and member of the Rubin Observatory scientific advisory committee. “And in addition, it’s stacking the frames of that movie to get a really deep image. That will give us a map of all of the galaxies, which traces where all of the matter is, which is mostly dark matter. We’ll see what the universe looked like billions of years ago and learn more about what dark matter is.”