The Vera Rubin Telescope is a movie camera for the universe

I don't often get too excited about telescopes. But this one's different.

In late June, the Vera C. Rubin Observatory (VRO), 2,650 metres up on a mountainside in Chile, began to release its first images of the universe. A facility more than 20 years in the making and operated by the US National Science Foundation and Department of Energy, the telescope is one of the most ambitious astronomical projects of our times. Its aim is to produce a more or less real-time movie of all the cosmos that is visible from its mountain perch.

The massive mirrors that focus light onto the telescope’s cameras will rotate to image the entire sky every three days, before repeating the process indefinitely. Those images will be turned into a time-lapse movie in which all manner of changes will be visible, ranging from the movements of small objects in our own solar system to the explosions of distant stars and the paroxysms of black holes at the centres of other galaxies.

And because all the images will be superimposed to create an intergalactic movie, even incredibly faint objects should slowly come into view, giving the telescope a deeper view into the universe than any before. It will offer the closest we have yet come to a comprehensive map of the visible cosmos.

Vera Rubin was an American astronomer whose studies of galaxies were central to the discovery of dark matter, the mysterious and still hypothetical stuff that provides the gravitational glue holding galaxies together. She was repeatedly tipped for a Nobel prize until her death in 2016. Naming the observatory after her – a decision made in 2019 – redresses some of the injustice of having been overlooked by the Stockholm committee.

Everything about the $800m VRO seems record-breaking. The moveable part of the instrument weighs 350 tons, and its main reflecting mirror is 8.4 m across and took seven years to make. The main camera alone weighs 3 tons. In just one year of operation, the telescope will collect more data at visible-light wavelengths than have all previous optical telescopes combined. The first trial runs were conducted last October, and even now the images it has produced are still preliminary: the survey proper won’t start until the winter.

What kind of things might the VRO see? In our neighbourhood – aside from the confounding rash of satellites that crisscross the night sky, not least the 7,500 or so Starlink swarm owned by Elon Musk’s SpaceX – there are millions of asteroids and other small solar-system objects yet to be discovered, offering a more complete picture of what else orbits the Sun. The telescope might increase our inventory of such objects tenfold or more. Our backyard may also host lumps of rock and ice somehow ejected from other solar systems, just passing through on a journey through interstellar space.

In our galaxy, the observatory will see stars that pulsate in brightness, called Cepheids, which are used to calibrate measurements of cosmic distance. It will also spot supernovae – exploding stars – in our galaxy and others. Indeed, it is estimated that it may see as many as a thousand supernovae every night. Astronomers hope also to spot extreme and rare events called kilonovae: outbursts caused by the merging of two neutron stars, the superdense remnants of collapsed stars that are created in some supernovae.

The VRO will also see many previously unknown galaxies, including smaller ones called dwarf galaxies that are often too dim to see. Getting a clearer picture of the variety of galaxies should help to understand how they form – at present, our understanding of that is skewed by the limitations on what we can see.

Some of the most exciting observations might be of galaxies in the process of merging, as many do (our Milky Way galaxy may merge with the nearby Andromeda galaxy in a few billion years’ time). These events aren’t as dramatic as one might think, since so much of a galaxy is empty space. But at the heart of most galaxies (including ours) is a supermassive black hole, and a merger should draw these together, causing episodic flashes of brightness from the disks of hot material surrounding them. Such cataclysmic events create gravitational waves – ripples in spacetime itself, which can be detected by gravitational wave observatories on Earth such as LIGO in the US. The VRO might show us for the first time what black-hole collisions look like at visible wavelengths.

Appropriately enough, the VRO might also tell us more about dark matter, for example by spotting how the gravitational influence of lumps of it distorts the light from more distant objects behind them in our line of sight, an effect called gravitational lensing. Vera Rubin would have been delighted by that.