When he started his doctorate in the United States, cosmologist Pedro Bernardinelli, 27, did not expect to find comets. “That wasn’t the idea. What happened was really luck,” he says.
In April of this year, he found a huge star in a table filled with data about objects scattered across the Universe. But not only that: it was the largest comet known to mankind, about 2.5 times larger than the previous record holder.
Days later, the then-comet C/2014UN271 changed its name to Bernardinelli-Bernstein, a tribute to the Brazilian scientist and his doctoral advisor, Gary Bernstein. “There was a process to change the name, but it lasted a few days. They asked me to keep it a secret. It was a funny experience,” he says.
The new star had already been detected for the first time in 2014, but there was little information about him. Until this year, he was just a speck of light in thousands of pictures of the sky taken by telescopes observing the universe. That’s why it took the tentative nickname, a number. Now, from the analysis of the Brazilian, we know that it is about 4.5 billion years old and has a diameter of 150 km (distance between Rio de Janeiro and Cabo Frio or São Paulo and Bertioga), the largest ever recorded.
He’s also coming towards Earth, but there’s nothing to worry about. The data show that the comet will reach the closest point to the Sun in January 2031, and still be at a distance of 11 AUs (about 1.5 billion kilometers, close to Saturn’s orbit).
“A joke I usually tell: saying that this object is heading towards Earth is not wrong, because it really is. But it’s the same thing as saying that, every time I receive my salary, my fortune comes close to Silvio’s fortune. Santos. Technically it’s right, but it doesn’t mean it’s going to get there,” jokes the cosmologist.
The Brazilian is part of the Dark Energy Survey (DES), an initiative with university students from eight countries, including Brazil. Collaboratively, the group’s goal “is to map hundreds of millions of galaxies, detect supernovae and find patterns of cosmic structure that could reveal the nature of dark energy that is accelerating the expansion of the Universe,” according to the initiative’s website.
According to DES, the comet discovered by the Brazilian is “about a thousand times more massive than a typical comet, making it arguably the largest comet discovered in modern times”.
Bernardinelli’s doctorate and research project had another focus: measuring the size of galaxies and the influence of dark matter on the Universe.
But in an analysis of data gathered over the past six years, he and other colleagues have begun to find some “Trans-Neptunian objects,” stars that are beyond the orbit of Neptune, the eighth planet in the Solar System.
“The great grace of these objects is that they are a kind of rubble from the formation of the Solar System, they are the debris that were kicked away. It is very worthwhile studying them because, with them, it is possible to reconstruct the history of the Solar System” , it says.
This year, Bernardinelli came across a comet larger and a little closer than Neptune while analyzing a table with thousands of numbers that represent stars detected in images taken by telescopes.
“It was pure luck, a fluke. He was right at the limit of what was possible to recover with the data. It was very obvious that it was something different,” he says.
The comet soon caught the attention of the cosmological community as it is a typical star coming from the Oort Cloud, a region in the outer reaches of the Solar System (after Uranus and Neptune) and supposedly occupied by billions of objects that orbit the Sun.
The orbits of these stars are considered “eccentric”: they can get very close to the Sun and then become extremely distant. Most long-cycle comets from the Oort Cloud take thousands and even millions of years to complete this loop around the star.
Last year, a comet called C/2002 F3 (Neowise), coming from the Oort Cloud, could be seen from Earth during the summer in the Northern Hemisphere. It was a unique opportunity, as it will only pass through the planet again in 6,800 years.
The Bernardinelli-Bernstein, with a “flattened” orbit, has an even longer path. “We know that it passed through the Solar System about 3.5 million years ago and that objects like it were kicked into the Oort Cloud 4.5 billion years ago. So we estimate it to be that age,” he says. the scientist.
The comet will have its perihelion (when it gets closer to the Sun) on January 21, 2031. “That’s when it gets brighter for someone watching from Earth,” says Pedro Bernardinelli.
This ten-year period for perihelion is a positive point of discovery, according to the cosmologist. “We took this object very far from the Sun, and this is not always the case. We still don’t understand what comets do when they are very far from the Sun. We have ten years to monitor it, it’s an incredible opportunity”, it says.
Starting in 2023, an observatory called LSST (Large Synoptic Survey Telescope) in Chile, whose objective is to find objects in the Universe, will start taking pictures of the entire sky every three days. For the Brazilian scientist, the initiative will help to better understand the comet that bears his name. “The best way to describe it is that we will have a picture of him every three days, we will have a movie of him moving around the Universe”, he explains.
‘very boring’ work
Pedro Bernardinelli was born in Itaquera and grew up in Vila Matilde, both on the outskirts of the east side of São Paulo. “When the entrance exam arrived, I liked physics and computers, so I chose Physics, because it combined the two”, he says.
He entered USP and graduated in 2015. During his graduation, when he began to study the Universe, a professor convinced him to skip his master’s degree and try for a doctoral scholarship at some university in the United States. He got it at the University of Pennsylvania, where he joined the Dark Energy Survey.
The work of a cosmologist itself, says the scientist, can be quite tedious. Therefore, the image of an ordinary person who discovers a comet that will destroy the Earth by looking through a telescope in the window of his house is not true (as in the catastrophe movie “Deep Impact”).
“That’s not how it works. In fact, you spend days and days looking at tables with thousands of numbers and trying to find something there. The job is basically processing data in a supercomputer”, he says.
This is how it happened with comet Bernardinelli-Bernstein. “After the table, the verification process was essentially spending hours and hours looking at black and white images with a very faint ball in the middle to see what this object was,” he explains.
“This is a very boring thing. I had to stop every half hour, open the window to rest my eyes, I was already seeing everything in black and white”, he says.
In recent months, Bernardinelli has embarked on a postdoctoral degree at the University of Washington in Seattle. Now, he intends to better study the comet that bears his name. There are many things to discover, he says.
“We still don’t understand what comets do away from the Sun. We are interested in knowing what processes occur on the surface of these objects, such as the melting of ice when the Sun approaches”, he explains.
The cosmologist and other scientists also want to know how many of these stars exist. “This is the first comet of this size ever seen. But is it unique or are there others? What is the population of these objects in the Solar System?”, he asks.
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