“There are so many stars!”
This might sound like an obvious thing for a professional stargazer to say. But astrophysicist Federica Bianco was reacting to something extraordinary — the first full-colour picture from a telescope that promises to image vastly more stars than any that came before it.
Bianco and her collaborators got a sneak peek at the sky as seen through the Vera C. Rubin Observatory, a US$810 million, US-led facility that is due to start full operations in the coming months at its 2,647-metre-high site on Cerro Pachón in Chile. To be seen at full resolution, each of Rubin’s 3,200 megapixel shots — captured with the world’s largest digital camera — would take several hundred high definition (HD) television screens put together.
The Rubin Observatory will map the entire southern sky every three to four nights, observing each spot around 800 times over its ten years of planned operations. Eight science collaborations will sift through the data it produces, each focusing on different questions, from mapping the history of the Universe and its dark matter contents to tracking potentially dangerous objects in the Solar System.
The observatory will also capture an unprecedented number of transient and variable astronomical events in real time — stars whose brightness changes unpredictably, for example, and those that explode or suddenly disappear. “We are going to be able to release alerts worldwide on anything that moves or changes brightness — 8 million alerts per night,” says Tony Tyson, an astronomer at the University of California, Davis, who first conceived of the concept for the telescope in the 1990s.
The team will unveil the inaugural image on 23 June; in the meantime, the researchers are keeping quiet about what it shows. “We’ve been very serious about keeping it capped, so that we can do a big reveal,” says Bianco, who is at the University of Delaware in Newark.
Way, way beyond HD
The Rubin Observatory’s telescope, named the Simonyi Survey Telescope after the philanthropic foundation that contributed to its construction, will not be the largest eye on the sky. With a diameter of 8.4 metres, its primary mirror will not collect quite as much light as the handful of bigger telescopes currently in operation, let alone the 39 metres of the European Southern Observatory’s Extremely Large Telescope, which is expected to come online in 2029, also in Chile. Nor will Rubin peer as far back into the past as the James Webb Space Telescope, which can sense longer wavelengths of infrared light on account of being in space, and can therefore image more distant objects.
But where Rubin will excel is in its ability to image large swaths of sky — capturing an area of the night sky equivalent to 45 full moons in each shot — and to do so at a staggering speed.
Tyson came up with the concept for the telescope while he was helping to pioneer digital sensors that could replace photographic plates at the world’s optical observatories. Tyson says he realized that Moore’s law — which states that the number of transistors on a chip doubles every two years or so — meant that computers would soon be able to process staggering amounts of data, and that digital sensors would pack in more and more pixels. He could imagine taking larger and larger pictures that could map the Universe’s galaxies — and how images of these structures are distorted by clouds of dark matter.
The effort, originally called the Large Synoptic Survey Telescope, was named as a top priority in the US Astronomy and Astrophysics Decadal Survey of 2010. Construction started in 2015, after the US National Science Foundation and the US Department of Energy both committed funding. In 2019, the US Congress officially renamed the telescope after the late astronomer Vera Rubin, who pioneered the study of dark matter.
