Waiting for First Light

January is always a good time for looking ahead at the year to come. There are some fun space things coming up this year—new rockets, new spacecraft, existing spacecraft continuing to carry out their missions, not to mention sky events like meteor showers and a lunar eclipse.

But if I had to pick a single space/astronomy-related thing in 2025 that has me more excited than anything else, I don’t even have to think about it that hard. The answer, unquestionably, is first light on the Vera C. Rubin Observatory, currently scheduled for July. It’s going to be what we in the biz call “a game changer”. 

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What is it? Why is it going to make a huge splash in the astronomy world? Who the heck is Vera Rubin? SO GLAD YOU ASKED!

Meet Dr. Rubin

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Let’s start with the namesake. When originally conceived and during the first several years of its construction (which began in 2015), the observatory had the more technical name of the Large Synoptic Survey Telescope (LSST). It wasn’t until 2019 that it was officially re-dubbed the Vera C. Rubin Observatory, an honor excessively well-deserved and long overdue.

In a nutshell, Dr. Vera Rubin basically proved the existence of dark matter through her studies on galactic rotation and movement. That alone would make her an astronomy legend. But she did this as a working mother in the 1960s at a time when women in science were still very scarce, and she battled rampant sexism throughout every step of her early career. And considering she’s the one who cemented the discovery of the existence of the stuff that makes up a solid quarter of the universe, she never got the recognition she deserved. 

I was pumped when the announcement came in 2019 that LSST (which was a name that could best be described as unwieldy) had been officially renamed after Dr. Rubin. After all, it makes sense that the facility that could help stand modern astronomy on its head be named after someone who did the same.

Meet the Atacama Desert

Okay, so what is there to know about the Rubin Observatory? To put things in a nutshell again, it’s big, it’s in one of the best observing spots on Earth, and the amount of data it is going to generate is (to put it extremely mildly) absolutely insane.

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To get a little more detailed, Rubin is being built on Cerro Pachón, a mountain in central Chile. Mountains in general are good for observatories because they put the telescope above a good chunk of the atmosphere, and deserts are good for their lack of moisture (atmosphere, good for the rest of us, is the enemy of ground-based astronomy and why we love putting telescopes in space and moisture means clouds, which do no astronomer any good). 

The mountains of Chile are home to the Atacama Desert, one of the driest places in the world, and very sparsely populated, meaning all of the things an astronomer hopes for in an observing site are in one place. As a result, a huge percentage of the world’s major telescopes are found on Chilean mountains, despite the extreme challenges of building large facilities in such remote locations. The Rubin is only the newest to be completed. At least two other major facilities (the Giant Magellan Telescope and the European Extremely Large Telescope—yes that’s it’s real name) are currently still under construction there.

Cerro Pachón, the Rubin’s mountain home, is about 8,800 ft tall at its peak (the Rubin itself is a little ways down from the peak). It’s also the home of the Southern Astrophysical Research (SOAR) Telescope, and the Gemini South Observatory, so its bona fides as an observing site are already well proven.

Meet the Telescope

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While Rubin is the name of the facility, the telescope itself technically has its own name, the Simonyi Survey Telescope. It’s a big ‘un, with an 8.4 m primary mirror. That will make it the seventh-largest telescope in the world, and the largest in Chile—at least until the ones still in the early stages of construction get done. 

That’s the primary mirror. Most telescopes use a two-mirror system, a primary and a secondary, to help focus the light and remove color aberrations that can be caused by the curve of the mirror (or lens, in a refracting telescope). The Simonyi will actually achieve this using a complex, three-mirror system, giving it one of the sharpest views ever devised.

And then there’s the camera that attaches to the telescope to actually record the light it collects. This baby is intense. It’s the largest digital camera ever constructed. Seriously, it’s the size of a car. It has a 3200-megapixel view provided by an array of 189 CCD sensors. And together it and the Simonyi Telescope are going to create a whole lot of data.

Meet the Universe

As the “Survey” part of LSST suggests, this is a facility designed to take a wide view of the sky. This is different from, say, how something like Hubble or Webb operates. Those are designed to get extremely detailed views of a small area, so they tend to focus a single object at a time.

That’s not what the Rubin will be doing. Instead, it’s going to be looking at huge swaths of the sky every night, taking a 15-second exposure every 20 seconds and then repositioning. The triple threat of location, telescope sensitivity, and camera design mean that it’s perfectly equipped for making extremely detailed wide-field observations. It will be able to photograph the entire sky above it over the course of a few nights. And it’s going to do that over and over and over again.

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Why repeat itself so often? This is actually a handy way of getting to know the universe. For one thing, it’s exceptionally helpful for mapping the locations of things in exquisite detail. That’s important for things like understanding the shape of our own galaxy (we are, after all, trying to figure out what its outsides look like while stuck inside. It’s like trying to figure out what the outside of your house looks like when you’re trapped in the living room). 

Extreme mapping capabilities are also important if you want to learn more about things like dark matter and dark energy, which we cannot directly observe. We have to see the effects they have on the space around them, so being able to map that space in minute detail is one of the best way to understand these mysterious entities that make up 96% of the universe (and let’s face it, if the facility that figures out dark matter is the one named after Vera Rubin, that’s just poetic).

Looking at the same patches of sky repeatedly is also a good method for searching for things that are changing. This could mean changing position, i.e. things that are moving. The Rubin is expected to seriously increase the number of known Kuiper Belt Objects, which hang out around and beyond Pluto and are very faint and hard to see, by spotting them moving against the background sky. The Rubin also might be the thing that will finally prove if the mysterious Planet Nine does—or does not—actually exist.

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And then there are the things that are changing because they’re changing. Transient events like supernovae, gamma ray bursts, or microlensing events are things that happen out of nowhere and sometimes last for very short amounts of time, meaning observing them can be tricky. The Rubin’s constant sky-surveying will be just the thing for catching these things as they happen. The big hope is that the Rubin will help us see the events that generate gravitational waves. These happen so fast that, while we’ve been able to detect those gravitational waves from them, we haven’t been able to see the events themselves yet. 

All of this means that the Rubin is going to produce something like 20 terabytes of data every single night. To go through all of it in a timely fashion (necessary for detecting those transients) would be literally impossible for a human alone. The data management system being designed for the Rubin will go through all that data in real time, as it’s collected, and is expected to be able to send an alert out within a minute of the telescope detecting a transient event.

First Light

The Rubin was originally supposed to experience first light, the beautiful term for when a telescope first turns itself to the skies, this month. The 2020 pandemic wreaked havoc on that schedule, as it did with so many other things, but all told the delay will only be about six months. Come July the Rubin Observatory will crack open its ceiling and photons will begin to rain down upon the 8.4 m mirror of the Simonyi Survey Telescope, and first light will be achieved. It’s just the beginning.

And who knows, it might just solve some of the mysteries of the universe. One can imagine that Dr. Rubin would have been pleased.