While our universe floats in all directions like an indestructible balloon – thanks to dark energy, a force completely hidden from the human eye – Dillon Brout is an astrophysicist trying to understand everything.
Brout wishes to reveal the strange correlation that exists between the invisible and visible universes, to understand how the fabric of space-time flows and perhaps finally reveal the truth about whatever is causing the cosmos to move faster and faster by the day. bubbles out faster.
To do this, he collects supernovae.
However, when figuring out which supernovas to add to the shelf, Brout isn’t interested in all of them. These star explosions are generally divided into two main categories categories: Type 2 and Type 1a. Brout wants the Type 1a’s, and his reasoning is actually quite simple:
“They’re not all exactly the same, but they are very similar,” he told Space.com.
Related: How fast is the universe expanding? New supernova data can help determine this
To solve all those space mysteries mentioned above, you essentially need to measure some distances on cosmological scales. Only then can you know, for example, how far and how fast dark energy seems to be forced room to expand. From there, do the reverse math and you might also learn something about the nature of dark energy itself. But to measure even such vast distances and elusive concepts, to explore how far back we can see and how much further back that point moves, you still need something as basic as a ruler.
Fortunately, Type 1a supernovae, because they are so standardized in brightness and general behavior, are like the ticks on light years-long rulers diving through space. For this reason, astronomers even like to call them “standard candles.” They are perfect lighthouses that guide us as we calibrate our equations and search for answers. The more we have, the better.
In search of efficiency and accuracy, Brout fills his supernova collect by using machine learning algorithms that powerfully explore as many Type 1as as possible. (Another reason why Type 1a standardization is useful. Consistent algorithms like consistency.)
He is part of the Dark Energy Survey collaboration, and earlier this month, the team announced that their algorithms had managed to detect 1,500 of these luminous natural markers – in just five years. That’s a pretty big problem. For context, Brout says it took scientists 30 years of regular Type 1a searching (aka using a reliable spectrograph) to find the previous 1,500 subjects. DES got the same result in about an hour sixth of that time frame.
“One of the main things that made DES so special is that it covered such a large area of the sky,” Brout said, adding that he trusts his algorithms enough to say that comparing the same parameters is more or less not is needed.
But things are about to take off.
Although DES yielded an impressive number of Type 1as, its companion instrument, the Dark Energy Camera, covered only 30 square degrees of sky. That is a relatively small part, says Brout. Enter: the Rubin Observatory.
Or, more specifically, the Legacy Survey of Space and Time that will be made in part using the state-of-the-art LSST camera starting next year.
“LSST will observe the entire observable south night sky‘ said Brout. “You go from DES discovering 1,500 to LSST discovering a million alerts, and we’re going to hopefully filter that using machine learning and other algorithms to get a few 100,000 Type 1a supernovae.” “
One specific question waiting to be answered
Fortunately, the Rubin Observatory is officially on track to be fully constructed later this year and the LSST will begin its journey from the top of a Chilean summit early to mid next year, Victor Krabbendam, the observatory’s construction project manager, said at the 243rd meeting from the American Astronomical Society in January 2024. “We’re about a decade into the actual construction phase,” he said. “The sun is setting and we are getting close.”
And actually Brout already has a specific puzzle waiting to be solved with the LSST.
With their massive 1,500 Type 1a supernova flights announced this month, Brout and fellow researchers more or less confirmed what we currently know about what’s called “the cosmological constant,” which you can think of as the value that dark energy represents in the expansion equations of the universe. It explains the gear piece that normal physics cannot fully explain. This ‘confirmation’ may sound disappointing at first, but in a way it’s quite good progress. It means that one of the most accurate calculations of the universe’s expansion tells us that we are probably right about everything we know so far about dark energy.
Perhaps even more interesting, though, is that the team’s work also indicated a strange pattern. “We have a section in the article that combines all available studies of dark energy, not just supernovae, and what we see is that many of them point to a slightly larger value of the ‘equation of state’ of dark energy, which would imply that it is not a cosmological constant.”
In other words, that would mean there is no value to represent dark energy. Maybe it’s flexible.
“One of the main benefits we get from this new LSST analysis is that we see many more supernovae in the nearby universe, and that’s because we cover such a large part of the sky,” Brout said. “If you think about it, the nearby universe is the universe that, because of the speed of light, we see the galaxies much closer than they are now. When you look at the distant universe, you see the universe when it was much younger.”
That’s important, he explains, because the effect of dark energy is believed to be strongest in the recent universe. Why? This is where things get really weird.
“Dark energy, we think, is a property of space itself,” Brout said. “That’s kind of what the cosmological constant embodies, which is like the energy of empty space.”
So if dark energy is a property of empty space, that would mean there is more dark energy in the universe today than in the past. This is because the universe is expanding, creating more ‘space’.
“We think it doesn’t dilute as the universe expands,” Brout said, “so that means that, relative to the amount of matter in the universe and dark matter in the universe you get more and more dark energy.”
At this point you may be wondering, I’m sorry, what? I thought the universe is enclosed? Where does the new dark energy come from? It can’t just happen, right?
“That’s the million-dollar question,” Brout said. “Is it just a property of space? Is this a fundamental property of the universe? That as space itself expands, you naturally get more dark energy with it?”
And to get to the bottom of this, there’s a multi-million dollar camera ready to go soon.
The golden observatory of 2025
There are still four major steps to go before Brout can start counting the days leading up to the first light of LSST. First, the Rubin team needs to get some important mirrors ready for use. Next, the crew must grab the glass needed for the Simonyi telescope – which reportedly passed tests without even the right glass part – and then mount the commissioning camera. Finally, the approximately $200 million LSST camera, currently being assembled on the West Coast, will earn its place.
“You still have to take that from California to the top. It’s a very delicate instrument. It’s special in the sense that it’s a $200 million camera — irreplaceable,” Krabbendam told Space.com.
“It’s a huge camera,” he said. “It’s 3.2 gigapixels for a focal plane.”
Related stories:
— The mysteries of the dark universe could be solved by the Rubin Observatory
— We still don’t know what dark matter is, but here’s what it isn’t
— Hypothetical ‘dark photons’ could shed light on mysterious dark matter
One gigapixel, for context, is equal to one billion pixels; a standard DSLR camera operates on megapixel scales, or millions of pixels. To really drive home this point, think of how a million seconds is 12 days; one billion seconds is 31 years. So… imagine the resolution of the camera power scanning the entire observable southern sky.
This is why the observatory, built with about $500 million in funding from the National Science Foundation and a few $100 million in funding from the Department of Energy – the latter of which is particularly interested in studies of dark energy like Brout’s.
So long awaited.
Update 2/1: 1 million seconds equals 12 days. This article has been updated to reflect that.