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In Atacama, microwave telescopes operate at extreme altitude to capture ancient signals from the cosmos, while a Brazilian astrophysicist coordinates part of the scientific routine between data, engineering, and severe weather conditions.
The Brazilian astrophysicist Jullianna Denes Couto works at CLASS, a project installed in the Atacama Desert, in northern Chile, which uses microwave telescopes to investigate signals related to the early phases of the Universe.
The structure operates at about 5,200 meters altitude, in an area used by international astronomical observation programs due to the atmospheric conditions favorable for capturing this type of signal.
CLASS, an acronym for Cosmology Large Angular Scale Surveyor, observes the so-called Cosmic Microwave Background, radiation remaining from the period when the Universe became transparent to light.
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According to NASA, this process occurred about 380,000 years after the Big Bang, when atomic nuclei began to capture electrons and light could travel long distances.
The project focuses on measuring small variations in temperature and polarization of this radiation.
In an interview with CNN Brazil, Jullianna stated: “We observe approximately 75% of the entire visible sky from Earth every day, measuring small variations in temperature and polarization of the background radiation of the Universe.”
CLASS observes signals from the Universe in the Atacama sky
The research is led by Johns Hopkins University, in the United States, and receives support from the National Science Foundation, according to information published on the official CLASS website.
The telescopes are located in the Atacama Astronomical Park, in Chile, under the responsibility of the Chilean research and development agency.
The project’s proposal is to use polarized light associated with the Big Bang to study when the first stars began to illuminate the Universe, a stage known as the cosmic dawn or reionization.
CLASS also states that its data can contribute to research on the galaxy, the Solar System, neutrinos, and dark energy.
Among the topics investigated is cosmic inflation, a term given to an accelerated expansion that, according to NASA, is believed to have occurred in the first moments of the Universe’s history.
The agency states that scientists still do not know what came before this period or what mechanism would have driven the expansion.
In 2025, CLASS announced a new measurement of the so-called optical depth of reionization, a parameter used to estimate the probability of a photon from the Cosmic Microwave Background interacting with electrons released by intergalactic gas after the emergence of the first stars.
The result combines data from CLASS with information from the Planck and WMAP missions.
Cosmic Microwave Background helps to study the beginning of the Universe
The Cosmic Microwave Background is treated by cosmologists as the oldest observable light.
It does not appear as a common image, but as a faint microwave signal distributed across the entire sky.
NASA describes this glow as the record of a phase when the Universe ceased to be opaque and began to allow the propagation of light.
Before this period, matter was in a hot and dense state, with free electrons scattering the radiation.
As the Universe expanded and cooled, neutral hydrogen atoms formed.
With fewer free particles to scatter the photons, light began to traverse space.
Reading this signal requires instruments capable of separating emissions of cosmic origin from interferences produced by the atmosphere, terrestrial sources, and the Milky Way itself.
According to Johns Hopkins, microwave signals associated with the cosmic dawn are difficult to measure from Earth due to factors such as radio, radar, satellites, weather, and temperature variations.
For this reason, the CLASS telescopes were designed to map large areas of the sky and measure the polarization of the Cosmic Microwave Background at microwave frequencies.
Studies published by researchers from the project indicate that the survey covers about 75% of the sky from the Atacama.
Work in Atacama includes engineering and maintenance
The operation of CLASS also involves tasks of engineering, maintenance, logistics, and equipment management.
In the report published by CNN Brasil, Jullianna states that the astronomy conducted in observatories of this type is not limited to nighttime observation through a telescope.
“A large part of my work involves engineering, maintenance, logistics, project management, and troubleshooting extremely complex equipment,” said the astrophysicist.
The description points to a routine where data collection depends on the stability of the instruments and the ability to respond to technical failures in a hard-to-reach environment.
The conditions in Atacama also impose physical and operational restrictions.
According to Jullianna, at the location where the telescopes operate, the atmospheric pressure is about half of that recorded at sea level.
The researcher also stated that the lowest temperature ever recorded at the observatory was approximately -45°C and that, in winter, winds can exceed 100 km/h.
At high altitude, the availability of oxygen is lower, which can make simple tasks more demanding.
For the equipment, the combination of cold, wind, and climate variations demands constant maintenance, protection of sensitive components, and planning access to the observatory.
Atacama Desert offers conditions for astronomical observation
The Atacama Desert is used by international observatories because it combines altitude, low humidity, and skies with favorable conditions for astronomical measurements in different ranges of the electromagnetic spectrum.
In the case of CLASS, the official site states that the project is located in northern Chile and uses technology aimed at detecting weak signals from the Cosmic Microwave Background.
The presence of Brazilian researchers in the project was recorded by IFMG Campus Formiga in May 2026.
The institution reported that Jullianna Dénes Couto and Deniz Augusto Nunes Valle, both affiliated with Johns Hopkins University, participated in a scientific outreach activity on astronomy and cartography.
In the publication, IFMG presented the two as operational managers of the CLASS telescope and stated that they work at the research center installed in Atacama.
The activity was themed “From Atacama to the Big Bang: The Universe as an Observable Fossil” and was part of the project “Under the Sky of the Rio Formiga Valley.”
Brazilian astrophysicist works between data and scientific instrumentation
Jullianna’s journey in Atacama also illustrates the intersection between astrophysics and scientific instrumentation.
In an interview with CNN Brazil, she reported that she had no direct experience with instrumentation when she accepted the position and compared the change to Schrödinger’s cat experiment, referring to the uncertainty about the outcome of the decision.
“Until I accepted the position, there were two possible outcomes: the best decision of my life or a complete disaster. Nine years later, I think we can conclude that the cat survived,” she said.
The statement was maintained to record, in the first person, the researcher’s professional context without adding external evaluation to the account.
In the scientific aspect, CLASS aims to reduce uncertainties about ancient periods of the Universe by comparing its data with measurements from space missions like Planck and WMAP.
According to Johns Hopkins, researchers have managed to use ground-based telescopes to observe effects of the first stars on the light emitted after the Big Bang.
The analysis of these signals allows investigation into how the primordial gas was transformed by the radiation from the first luminous sources.
According to NASA, reionization advanced as the ultraviolet light from the first stars separated electrons and protons in hydrogen atoms, making the Universe progressively more transparent to light.
In this scenario, the telescopes installed in Atacama function as instruments to measure traces of processes that occurred billions of years ago.
The combination of altitude, detection technology, data analysis, and continuous operation allows CLASS to track weak signals that help reconstruct early stages of cosmic history.
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