In the first half of 2020, Brazilian astrophysicist Stela Ishitani Silva received an alert in one of the systems she uses at work: a star she was observing had an unusual peak of light.
It was the beginning of a journey that would take the 28-year-old miner, who works as a researcher for NASA (the US space agency), to lead a search that discovered a new planet – at least 26,000 light-years from Earth.
The star was named MOA-2020-BLG-135Lb — a word she knows by heart and scrambled, so proud was she to lead the research, which involved 36 scientists from different parts of the world — and it is an exoplanet, that is, a star that is outside our solar system.
To get an idea of ​​the distance of the planet discovered by her, 26,000 light-years means that, if an aircraft could travel at the speed of light, that is, at 300,000 kilometers per second, it would take 26,000 years to travel from Earth to Earth. star.
For four years as an assistant researcher at the Goddard Space Flight Center, a NASA laboratory in Washington, DC, Stela says that the idea of ​​working at the famous American agency always seemed absurd to her.
“When I decided to study physics, my family would joke, ‘But why, to work at NASA?’ And I thought ‘how silly these people are, it’s not like that, nobody works at NASA”, says the researcher, who fulfilled the family’s prophecy after graduating in physics at UFMG in 2016.
It was from a lecture by Brazilian astronomer DuÃlia de Mello, a professor at the Catholic University of America (also in Washington), that Stela discovered that yes, some people worked at NASA.
Passed her doctorate at the same Catholic University — she studied her doctorate simultaneously with her master’s degree, which she concluded in 2019 —, she studies precisely how to facilitate the search for new planets outside the solar system through artificial intelligence, automating data from millions of observed stars. .
In the case of MOA-2020-BLG-135Lb, the peak of light alerted by the Brazilian-style system indicated that a phenomenon called gravitational lensing was probably happening there.
“Have you ever seen that Whatsapp sticker where a person throws a ball over a net, and the net sinks?” questions the young woman, when the report asks the researcher to explain the phenomenon.
What Stela is trying to explain is basically Albert Einstein’s theory of general relativity, according to which the gravity of objects causes space-time to warp. This curvature ends up working as a kind of lens, increasing the amount of light observed coming from the star, as if it were a magnifying glass.
Months of research later, it became clear that the alert Stela received of an unusual light spike was nothing more than a planet passing in front of the star, and the space-time distortion caused the equipment to capture much more light.
“It was the object’s gravity that generated the effect of a lens. This allows us to observe dimly luminous objects, which we would have difficulty without knowing this phenomenon”, she explains.
Gravitational lensing also facilitates the detection of more distant exoplanets — the distance of MOA-2020-BLG-135Lb from Earth varies by calculation, but is between 25,800 light-years and 27,100 light-years.
The first exoplanets were discovered in the early 1990s, and today NASA registers 5,071 such stars, in addition to having another 8,870 candidates, which have not yet been confirmed.
There are different types of them. The planet discovered by Stela is of the Neptune class, as it is similar in size to the planet in the solar system. While Neptune has 17.1 times the mass of Earth, the exoplanet identified by the Brazilian has between 11.3 and 25 times the mass of Earth. Planets of the type generally have atmospheres dominated by hydrogen and helium with cores or rocks and heavier metals.
This is the first exoplanet discovered in a research led by Stela, but the Brazilian has already participated in the identification of a series of other stars with the research group of which she is a part, the MOA (Microlensing Observations in Astrophysics Collaboration), which brings together scientists in the USA , Japan and New Zealand.
In addition to distant planets, the group was part of the discovery of the first isolated black hole — wandering without interacting with other objects — known to exist, about 5,000 light-years from Earth.
Outside the MOA, Stela also participated in work with other researchers, most of them at NASA, who detected 181 exoplanet candidates using artificial intelligence.
In this case, the method used to identify potential planets was not gravitational lensing, but a technique called planetary transit, one of the most common ways to find exoplanets. In the case of planetary transit, when a planet passes between its star and the observer, it causes a kind of eclipse by blocking part of the light emitted by the star. It is by observing this drop in the amount of light emitted that astronomers identify the possibility of a planet in that star.
