The revolutionary Vera Rubin Observatory will collect more astronomical data in its first year of operation than all other telescopes combined. Astrophysics, as many astrophysicists will tell you, is the story of everything.
The nature and evolution of stars, galaxies, galaxy clusters, dark matter and dark energy - and the attempts to understand it all - allow us to ask the most important questions and seek the most important answers.
But practitioners of these sciences, as the late astronomer Vera Rubin wrote in the preface to her autobiography, "seldom emphasize the enormity of our ignorance."
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No one promised that we would live in an era that would unravel the mysteries of the cosmos," Rubin wrote. Yet the new observatory named in her honor, which will soon open its eyes, will bring humanity closer than ever to unraveling some of them. It will be possible because the Vera Rubin Observatory will do something revolutionary, rare, and relatively old-fashioned: it will simply look at
the universe and see what's out there.
Perched on top of a mountain in the Chilean Andes, the telescope is fully assembled and ready to go, although scientists can't use it yet. A few weeks of testing remain to make sure its camera - the largest in the history of astronomy, with a lens of more than 1.5 meters - works as it should.
Engineers are observing how
Earth's gravity causes the telescope's three huge glass mirrors to deflect and how that slight deflection will affect the collection and measurement of individual photons, including those that traveled billions of light-years to reach
Earth. They also watch as the 350-ton telescope will quickly sweep a panorama across a sky equal to seven full moons, stabilize and come to a complete stop, and then take two 15-second exposures before repeating the whole thing over and over again throughout the night.
So the telescope plans to survey the entire sky visible from Earth's southern hemisphere every three nights, creating a map of it over and over again and noting how it changes. And researchers are finalizing plans for how to sift through 20 terabytes of data every night, 350 times more than the data collected every day by the famed
James Webb Space Telescope.
Other specialists make sure that among the constant stream of images coming from the Rubin Observatory, interesting objects or unexpected cosmic surprises are not missed. The software will look for differences between each map and send alerts about each one; up to 10 million alerts about potential new objects or changes in the maps can be received overnight.
From searching for asteroids passing close to Earth and tiny stars called brown dwarfs to studying the smooth rotation of entire galaxies formed by
dark matter, the Rubin Observatory mission will cover the entire spectrum of visible-light astronomy.
The telescope will continue to map the sky for 10 years. It may be better equipped to answer astrophysicists' deepest questions than any observatory built to date.
"The potential for discovery is huge," said Christian Aganze, a space archaeology specialist at Stanford University who will use the observatory's data to study the history of the Milky Way.
More specifically, the Rubin Observatory will collect more data in its first year than has been collected by all telescopes in human history. This will double the amount of information available to astronomy - and to anyone trying to understand man's place in the Universe.
Rubin Observatory Mission
The observatory's purpose was not always so broad. Originally named the Large Synoptic Survey Telescope (LSST), the Ruby Observatory was proposed as an instrument to search for dark matter.
Vera Rubin has found the first strong evidence for the existence of what is now called dark matter - a gigantic amount of invisible matter that shapes the universe and determines the motion of galaxies in it.
She and her colleague, the late astronomer Kent Ford, were studying the dynamics of galaxies when they made this discovery in the 1970s. In a spiral galaxy such as the Milky Way, the galaxy's core contains more stars and therefore gravity than the outer arms. This should mean that objects closer to the core rotate faster than objects on the outskirts.
By observing the movement of stars and how their light changes as a result, Rubin and Ford found that stars at the outskirts move as fast as those closer to the center. They found that this phenomenon was observed in dozens of galaxies they studied. This pattern was unexplainable unless there was some additional invisible matter in the far reaches, causing the galaxy to spin faster at what only appears to be its outer edges.
Such dark matter had been proposed as early as the 1930s, but Rubin's discoveries demonstrated its effects on ordinary visible matter and provided the first evidence for its existence. "What you see in a spiral galaxy is not what you get," Rubin once wrote.
To date, no one has directly seen dark matter or understood its physical nature, including the particles that make it up. The original plans for LSST were to shed light on dark matter by mapping its distribution throughout the Universe through its gravitational effects.
Photo: scientificamerican.com
Astronomers also wanted to study
how space expands, thanks to the action of an equally mysterious concomitant force called dark energy. But when telescope development began, astronomers quickly realized that LSST could do much more than study dark matter - it could study just about anything, visible and invisible.
"This is not a telescope to which you will send proposals asking, 'I want to look here.' Its purpose is to do a full survey," said Gilhem Megias Homar, a doctoral student at Stanford University and a member of the telescope preparation team.
Mirrors and cameras
An open survey mission is a boon to astronomers, but it comes with serious design challenges. The telescope must move across a patch of sky in just a few seconds and stop shaking almost immediately for the images to be sharp.
At other observatories, where astronomers choose their targets in advance and plan what they will look for, telescope engineers have about 10 minutes to stop the glass from wobbling between surveys. Rubin Observatory has five seconds, says Sandrine Thomas of the U.S. National Science Foundation's National Optical and Infrared Astronomy Laboratory (NOIRLab), deputy director for observatory construction.
"When you want to move a mass like that very quickly and ensure stability, you can't have a very long telescope or the top will wobble," she says. "The light can't travel very far before it loses focus, and that creates a lot of problems."
To make the system more compact, the Rubin Observatory's main telescope has a unique three-mirror design.
The primary and tertiary mirrors were made from the same piece of glass. Light is reflected from the ring-shaped primary mirror and directed upward into a separate secondary mirror, which is itself the largest convex mirror ever made. The secondary mirror again reflects light back to the tertiary mirror, which is inside the outer ring of the primary mirror.
The tertiary mirror reflects light into the camera's sensitive detectors. The primary and tertiary mirrors together give the telescope a collecting area of 6.67 meters. The secondary mirror has a 1.8-meter diameter hole in the middle that houses the camera and its electronics. The tertiary mirror also has a hole for equipment designed to level the telescope and prevent it from wobbling. The camera is a 10 by 10 meter steel cube, small and compact.
Margo Lopez, a mechanical engineer, joined SLAC National Accelerator Laboratory after graduating from the California Institute of Technology in 2015 and has been working on the chamber structure ever since. "The goal of this project is to collect a huge amount of data," she says. "To do that, we need to see more sky at one time, take more pictures at night, and get more detail in each photo - those are the three ingredients for success."
Photo: scientificamerican.com
Astronomers often use the disk of the full moon to describe a telescope's field of view; for an optical telescope, the Ruby Observatory's view is unrivaled. The
Hubble space telescope observes about one percent of the full
Moon, and JWST observes about 75 percent of the Moon's disk. Each Ruby Observatory image covers an area about 45 times the size of the full Moon.
"We just see so much more of the sky in every picture we take, and we get as much or more detail even though the field of view is so large," Lopez says.
The camera can take images using six filters, from near ultraviolet to near infrared. But astronomers need to understand how the camera itself affects the images. Dark matter distorts the direction of photons coming from distant galaxies, but so does the optical system.
"We really need to be sure about this. How does it affect the light itself? If there is turbulence in the atmosphere or in the optics, the point can become blurred," says Megias Homar. He spent his PhD program working on the Rubin Observatory's optical system to better understand this problem.
Observation from the top of the mountain
Once completed, parts of the telescope were to travel from California and Arizona to the summit of Cerro Pachon, a 2.5-kilometer seismically active peak in the Chilean Andes. Lopez and her colleagues rented a Boeing 747 cargo plane to bring the camera from San Francisco to Santiago, Chile, in May 2024.
The subsequent trip to La Serena, the town closest to the telescope's mountaintop location, required a 12-hour truck ride. Lopez followed every step of the journey, even dealing with a truck drivers' strike that threatened to block the road to Cerro Pachon. Finally, the camera made it to the very top of the mountain, where Lopez took it apart and checked everything out.
Teams of engineers, including Megias Homar, spent months testing the camera and its accompanying commissioning chamber, a smaller version of the real one that astronomers used to test all of the telescope's systems, which took to the sky in October 2024. Engineers switched to night work and slept during sunny hours, as astronomers do when they are at the observatory.
"This was the first time we saw the images. For a whole month I went to bed at 6 a.m. and felt like an astronomer," says Megias Homar. He has worked with the engineers and astronomers who planned and designed the LSST project since its inception. and told him that they began working on it as early as 1996.
Thomas has been part of the team for 10 years, but started as an observer on the mountain next door to the Ruby Observatory. "Bywhen I joined the project, I didn't appreciate how different this 'discovery machine' or even this observatory was," she recalls. "Providing this much data to the community, I think, will just have a huge impact."
For astronomers and astrophysicists, this wealth of data is almost dizzying. The Ruby Observatory's 10-year primary mission will provide a kind of still image of the cosmos that will show other observatories where to look for new discoveries. A decade is a short time in the history of the universe, but it's longer than anyone has ever looked at the sky.
The first light of the telescope
Cosmic archaeologists like Aganze hope to study the history of the galaxy and how dark matter may be shaping its evolution, just like the distant spiral galaxies that Vera Rubin saw half a century ago.
Recent studies, such as observations by the
telescope Gaia satellite, show that the Milky Way is surrounded by streams of stars that can shed light on the dark matter halo. Galactic streams can help astronomers understand when galaxies stop forming or how much dark matter must be around a small number of stars for it to coalesce into a galaxy.
With the Ruby Observatory, researchers will be able to see all the stars in a galactic stream, determine the shape of the stream, and even figure out what the associated dark matter should be. "And we could potentially do this for 100 or 200 galactic streams around the Milky Way," Aganze says.
"If small clumps of dark matter are messing up stars, we should be able to see it. We should even be able to put constraints on dark matter - is it cold, warm or hot?"," Aganze says, describing the three main theories of dark matter properties. "The Ruby Observatory will be great for this kind of science. We will definitely be able to push forward to the limits of galaxy formation and small dark matter halos."
The observatory will detect millions of new objects in the solar system, including 90 percent of all large asteroids passing Earth and thousands of tiny worlds far beyond the orbit of Neptune.
In fact, by producing frame-by-frame video footage, the observatory will reveal countless new transient and time-sensitive phenomena in deep space, such as quasars emerging from supermassive
black holes.
It will scrutinize a special type of exploding double star, called a Type Ia supernova, which is essential for astronomical measurements and may shed more light on the nature of dark energy.
Photo: scientificamerican.com
The astronomers plan to share images from the camera - a "first look," as they call it - on June 23, 2025. "I will worry about whether the optical system works; that's what I will think about first," says Megias Homar. And then he'll turn his attention to the main mission: space surveillance.
Astronomers who want to use the Ruby Observatory often talk about the value of simply observing the universe. Basic research is a public good, they say, that can provide new insights into history while improving the overall future.