Making frontier science means solving impossible problems in the remotest places on Earth.
Em um dos lugares mais áridos e elevados da Terra, uma astrofísica brasileira dedica seus dias a decifrar a luz mais antiga do universo — radiação emitida quando o cosmos tinha apenas 380 mil anos. Julliana Denes lidera o projeto CLASS no Atacama chileno, onde telescópios varrem três quartos do céu visível em busca de pistas sobre os primeiros instantes da existência. Seu trabalho mais recente produziu a medição mais precisa já feita da profundidade óptica da reionização, revelando quando as primeiras estrelas acenderam e transformaram o universo primitivo. É a ciência como arqueologia cósmica — e uma brasileira está entre os que seguram a pá.
- A 5.000 metros de altitude, instrumentos ultrassensíveis enfrentam variações extremas de temperatura e clima imprevisível, tornando cada dia de operação uma vitória contra o ambiente.
- A medição mais precisa já feita da profundidade óptica da reionização redefine nossa compreensão de quando as primeiras estrelas iluminaram o universo primordial.
- O Brasil não opera nenhum grande observatório astronômico próprio, mas seus cientistas ocupam posições centrais em projetos internacionais de ponta espalhados pelo Atacama.
- Denes, que chegou ao projeto sem experiência em instrumentação científica, transformou uma aposta arriscada em quase uma década de liderança técnica e científica.
- O CLASS avança na busca por evidências da inflação cósmica — a expansão vertiginosa do universo em suas primeiras frações de segundo —, uma das maiores questões em aberto da cosmologia.
A 5.000 metros de altitude no Deserto do Atacama, no Chile, a astrofísica brasileira Julliana Denes passa seus dias perseguindo luz que viajou por quase 14 bilhões de anos. Ela gerencia o projeto CLASS, um levantamento cosmológico que varre cerca de três quartos do céu visível todos os dias, medindo os vestígios de radiação deixados quando o universo tinha apenas 380 mil anos — a luz mais antiga que conseguimos detectar, um registro fóssil escrito em micro-ondas.
Com 38 anos e quase nove no projeto, Denes sabe que a astronomia real pouco se parece com a imagem popular do cientista solitário diante de um telescópio. Seus dias são consumidos por desafios de engenharia, manutenção de equipamentos e a resolução constante de problemas que surgem ao operar instrumentos sensíveis em um dos lugares mais inóspitos do planeta. O trabalho exige tanto rigor científico quanto improvisação criativa.
O projeto CLASS, conduzido pela Universidade Johns Hopkins, investiga questões fundamentais sobre os primeiros momentos do universo. No ano passado, a equipe publicou seu resultado mais significativo: a medição mais precisa já feita da profundidade óptica da reionização, um parâmetro que revela quando as primeiras estrelas se acenderam e começaram a transformar o gás primordial ao redor — uma aurora cósmica que marca uma das transições mais importantes da história do universo.
Denes chegou ao Atacama em um momento de virada em sua própria trajetória, sem experiência direta em instrumentação científica. Ela descreve a decisão como um experimento do gato de Schrödinger: poderia ter sido o melhor ou o pior passo de sua vida. Quase uma década depois, a resposta está clara.
O Brasil não opera nenhum grande observatório astronômico próprio, mas cientistas brasileiros tornaram-se peças essenciais em projetos internacionais espalhados pelo Atacama. Denes representa uma forma específica de liderança científica — não a que aparece nas manchetes, mas a que mantém projetos ambiciosos funcionando e traduz a ambição teórica em instrumentos apontados para o céu.
At 5,000 meters above sea level in Chile's Atacama Desert, a Brazilian astrophysicist named Julliana Denes spends her days chasing light that has traveled for nearly 14 billion years. She manages the CLASS project—a cosmological survey that scans roughly three-quarters of the visible sky each day, measuring the faint whispers of radiation left over from when the universe was barely 380,000 years old. It is, in other words, the oldest light we can detect, a fossil record written in microwaves.
Denes, 38, has worked on CLASS for nearly nine years, long enough to know that astronomy is nothing like the popular image of a solitary observer peering through an eyepiece at night. Her days are consumed by engineering challenges, equipment maintenance, logistics, and the constant problem-solving that comes with running sensitive instruments in one of Earth's most inhospitable places. The Atacama's extreme temperature swings and unpredictable weather create a hostile environment for the telescopes—a fact that transforms the work into something between astrophysics and mountaineering, requiring equal parts scientific rigor and creative improvisation.
The CLASS project, run by Johns Hopkins University and funded by the National Science Foundation, exists to answer fundamental questions about the universe's first moments. The team measures tiny variations in temperature and polarization across the cosmic microwave background, the radiation that filled all of space when the cosmos was still an infant. One of their central investigations focuses on cosmic inflation—the theory that the universe underwent an extraordinarily rapid expansion in its first fractions of a second, a period that would explain much of what we observe today.
Last year, the project published what Denes describes as its most significant result to date: the most precise measurement ever made of the optical depth of reionization. This parameter is crucial because it tells us when the first stars ignited and began transforming the primordial gas around them—a cosmic dawn that marks one of the universe's pivotal transitions. Understanding when this happened helps us understand how the universe evolved from a nearly uniform sea of hydrogen into the structured cosmos we inhabit.
Denes arrived in the Atacama at a turning point in her own career. She was finishing her degree in a different field and had no direct experience with scientific instrumentation. The decision to take the position felt like a gamble—she jokes about it as her Schrödinger's cat experiment, where the outcome could have been either the best decision of her life or a complete disaster. Nine years later, she has her answer. The work has proven endlessly challenging and absorbing, a constant negotiation between the demands of cutting-edge science and the practical realities of maintaining equipment in one of the planet's most remote locations.
Brazil itself operates no major astronomical observatory, yet Brazilian scientists have become integral to international research efforts scattered across the Atacama region. They work across a range of specialties—cosmology, astrophysics, and the development of scientific instruments themselves. Denes represents a particular kind of scientific leadership: not the kind that makes headlines, but the kind that keeps ambitious projects running, that solves the unsolvable problems, that translates theoretical ambition into working instruments pointed at the sky. Her work at CLASS is part of a larger story about how Brazilian science reaches beyond its borders to participate in humanity's effort to understand where everything came from.
Citas Notables
Observing the sky in microwaves means measuring tiny variations in temperature and polarization of the universe's oldest light, and doing so requires engineering, maintenance, logistics, and constant problem-solving on extremely complex equipment.— Julliana Denes, CLASS project manager
Frontier science in the Atacama is a hybrid of astrophysics, engineering, mountaineering, and creativity.— Julliana Denes
La Conversación del Hearth Otra perspectiva de la historia
Why the Atacama specifically? There must be other high-altitude deserts.
The Atacama is one of the driest places on Earth. That matters enormously for microwave observations—water vapor in the atmosphere absorbs the signals we're trying to detect. The altitude helps too, but the dryness is what makes it irreplaceable.
You said your work is mostly engineering and logistics. Does that feel like science?
Absolutely. People imagine astronomers staring through telescopes, but that's a tiny fraction of it. When you're measuring radiation from 14 billion years ago, the instrument itself becomes the experiment. Every problem you solve—every temperature fluctuation, every mechanical failure—teaches you something about the limits of what we can measure.
The optical depth measurement you mentioned—why does it matter when the first stars turned on?
Because it's a window into how the universe transformed itself. Those first stars ionized the gas around them, changed the entire structure of space. Knowing when that happened tells us how quickly the universe evolved from simple to complex. It's like knowing when a child learned to speak—it changes how you understand their whole development.
You came to this work without experience in instrumentation. Was that a disadvantage?
In some ways, yes. But it also meant I wasn't locked into how things had always been done. I had to learn by doing, which forced creativity. And honestly, after nine years in the Atacama, I can't imagine having done anything else.
What's the hardest part of the job?
The isolation, maybe. But also the weather. The Atacama looks empty and peaceful, but it's actively hostile to precision instruments. You're constantly fighting against temperature swings, dust, the sheer remoteness of it all. You solve one problem and three more appear.
What comes next for CLASS?
We keep refining our measurements, pushing deeper into the early universe's history. Every observation teaches us something new about inflation, about how the universe began. The work never really ends—there's always another mystery to chase.