A New 3,200-Megapixel Camera Has Astronomers Salivating

The Vera C. Rubin Observatory’s key instrument is almost ready to be installed on the telescope, where it will image tens of billions of cosmic objects.

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.”

Wechsler and her colleagues will also take advantage of the huge maps to study the expansion of the universe, investigate the Milky Way’s structure and its history, and probe the hidden skeleton of dark matter particles that are holding all the galaxies together. However, the third dimension of those 3D maps of the universe—the distance from Earth—will be uncertain, making them slightly fuzzy. But the researchers are prepared for that challenge, Wechsler says.

The Rubin team will release this data to the scientific community—which includes some 10,000 users—as soon as the images are processed, and they'll send out nightly alerts about objects that move or vary in brightness, so others can track the trajectories of nearby asteroids, for example.

The massive telescope, funded by the US National Science Foundation and Department of Energy, is named after astronomer Vera Rubin. In the 1960s and '70s, she used telescopes in Arizona to map out the spiral arms of stars of nearby galaxies. The rapid orbits of those stars—too rapid, if the stars were the only thing there—revealed a dilemma: Either there was hidden matter somewhere, or gravity works differently than physicists previously thought when it comes to the vast scales of a galaxy. Though Rubin was snubbed for a Nobel prize, her discovery led to research on dark matter.

Calling it the Rubin Observatory was a notable choice—it’s the first national observatory to be named after a woman. (The choice, announced in early 2020, has been popular and avoided the pitfalls of the Webb telescope, whose namers were criticized for honoring James Webb, a former NASA chief who was accused of enforcing discriminatory and homophobic policies at the agency in the 1950s and ’60s.)

But before Roodman and the rest of the team can pack up the camera to send it to Chile, they need to finish up their work in SLAC’s giant clean room, where technicians wear Tyvek “bunny suits” covering their hair, clothes, skin, and shoes. They must wipe down equipment they bring near the camera to ensure no stray strand of hair or dust grain falls on a sensor and diminishes its capabilities.

Their final testing regime includes checking the filters, the sensors, and the refrigeration systems needed for cooling them. After that, they’ll carefully package the camera, lens, filters, and the camera stand, and fly directly from San Francisco to Santiago on a Boeing 747 freighter jet. From there, it will be a short drive to the telescope, where the camera’s components will be reintegrated. And then those billions of cosmic objects await.

A New 3,200-Megapixel Camera Has Astronomers Salivating

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