Michel Mayor and Didier Queloz, two of the scientists awarded the 2019 Nobel Prize for Physics, were pioneers in discovering other worlds orbiting stars similar to the Sun.
There are countless examples in cinema, literature or comics, where the action takes place in other worlds far from our Sun. Planets outside the Solar System, planets that orbit other stars, have long been part of the collective imagination.
In the 1600th century, the philosopher Giordano Bruno argued that, beyond our world, the one we live in, God would have created an infinity of others. Unfortunately, this and other revolutionary ideas for the time cost him his life at the hands of the Inquisition in Rome in the year XNUMX.
More luck had Bernard le Bouvier de Fontenelle in the next century. Inspired by Copernicus' idea that the Earth and other planets would orbit the Sun, he assumed that the other stars would also have their cortege of planets and that there would be a multiplicity of worlds.
However, we reached the 4th century without finding evidence of the existence of these planets. Only the set that orbits our star, the Sun, was known. In fact, it is extremely difficult to get an image of a planet that is so far away, even in orbit of the star closest to us, XNUMX light-years away. Your image is completely overshadowed by the star's glare.
To get an idea of the difficulty astronomers face, let's imagine that we wanted to photograph a fly buzzing around a lightbulb of a farol, and that we observe this faroit several kilometers away.
the invisible dance
In 1952, the astronomer Otto Struve, an American of German descent, proposed a method for detecting the influence of the presence of a planet in orbit around it in the star's light.
In fact, no matter how small the planet, it always exerts some gravitational influence on its parent star. Imagine a mother and a baby, and this mother whirling around with the baby in her hands. It manages to run almost on itself at the same point. This “almost” is important, as she will always have to sway her body a little to compensate for the baby's weight.
The star also slightly oscillates due to the presence of the planet. However, when Otto Struve proposed this method, there were no instruments for analyzing starlight, called spectrographs, with sufficient precision to detect this minimal oscillation.
In the 1970s and 1980s, Michel Mayor (born in Lausanne, Switzerland, in 1942), a professor at the University of Geneva, studied the movement of stars in the vicinity of the Sun. its internal spiral structure.
He noticed that some stars, in addition to the main movement, showed a secondary oscillation movement, which seemed to indicate the presence of an invisible companion.
At this time, astronomers believed that, in addition to planets and stars, there would be intermediate bodies, then called “brown dwarfs”. The “brown dwarfs” would be more than ten times the mass of Jupiter, but less than one-tenth the mass of the Sun.
They would therefore not have enough mass to generate energy and light like the Sun and other stars, and would therefore be difficult to observe, but they would be able to exert some gravitational influence on the companion star they paired with.
In the early 1990s, using the Haute Provence Observatory, in France, Michel Mayor collaborated in the development of a new spectrograph, the ELODIE, with which he believed he could characterize the invisible companions of the stars he had studied. I could find out if they were these hypothetical “brown dwarfs” or even massive planets.
a bizarre planet
Michel Mayor then began to mentor a doctoral student, Didier Queloz (also Swiss, born in 1966). Queloz's investigation was not the detection of brown dwarfs, much less planets orbiting other stars, a too risky project at the time and one that would compromise his career. He was in charge of improving the algorithm for analyzing star observation data, making it faster and more efficient.
Michel Mayor and Didier Queloz were not pioneers in this research. It had been over fifteen years since the search for planets outside the Solar System in the United States.
But when looking for planets like Jupiter, which takes about 12 years to complete a return to the Sun, American colleagues patiently waited for signals that had equivalent time periods. Michel Mayor, on the other hand, had not imposed this time constraint, and was more open to whatever emerged in his remarks.
In fact, shortly after starting his project, in late 1994, Didier Queloz detected a sign in a very modest star in the constellation Pegasus. It was a signal with a period of only 4 days, which he thought was an instrument error. Mayor decided to wait a few months before new observations, in order to confirm whether or not it was some transient phenomenon in the star.
They repeated the observations at the beginning of the following year and again in July and September, and found that the signal was still there. It was a very bizarre thing, only possible to be produced by a planet with about half the mass of Jupiter but which orbited its star in just 4 days, that is, twenty times faster than Mercury completing one revolution of the Sun.
Furthermore, it was eight times closer to its star than Mercury is to the Sun. Something that we have no example in the Solar System.
In November 1995 an article was published in the scientific journal Nature announced the discovery of the first object with a mass comparable to that of Jupiter to orbit a star similar to the Sun.
This last part is important, as this is not the first exoplanet discovered. The first three exoplanets were discovered three years earlier, in 1992. However, they orbit, not a star, but the “corpse” of a star, a neutron star.
These three exoplanets would have survived the devastation of the explosion that destroyed the star, or would have been a second generation of planets formed from the remnants of the star after the explosion. In either case, they will be bathed in the neutron star's radiation, a radiation deadly to any life form we can imagine.
Interestingly, brown dwarfs were also discovered in 1994, but by another team, and also announced in an article in the journal Nature in September 1995.
the next revolution
In 2019, more than 4000 exoplanets are known. More than 250 were discovered by the group of Michel Mayor and Didier Queloz. The variety of planets discovered is enormous and surprising, but many have some similarities to Earth.
The Institute of Astrophysics and Space Science (IA) has a research group important and who has collaborated with Michel Mayor and Didier Queloz for many years. The researchers in this group are dedicated not only to detecting, but also to characterizing these new worlds, to find out how they are made and what they are made of.
In addition to being involved in space missions aimed at the study of exoplanets, such as the CHEOPS or the future ARIEL, of the European Space Agency (ESA), use a new generation spectrograph that we can designate as the great-grandson of the one used by Mayor and Queloz in the 1990s – the EXPRESS had a important Portuguese participation and the AI.
Who knows, maybe the team that leads the new revolution will be Portuguese: the discovery of signs of life in these new worlds.
Michel Mayor and Didier Queloz were awarded the Nobel Prize for Physics in 2019, an honor they shared with James Peebles, physicist and cosmologist.
"Stars that shine in time” is a rubric with which the Institute of Astrophysics and Space Sciences associates itself with the celebration of the 100 years of the International Astronomical Union (IAU), recalling important figures in the history of astronomy over the past 100 years.
Author Sérgio Pereira, Science Communication Group of the Institute of Astrophysics and Space Sciences.
Science in the Regional Press – Ciência Viva
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