He scours the universe looking for an Earth-like planet where life might exist. Nuno Santos took the risk of dedicating himself to astronomy in Portugal and now leads a team of excellence that competes for the best results on a worldwide level.
He says he has never counted the number of planets he has discovered, but we’ve got a number for him. Nuno Santos is part of a team that is associated to the discovery of 200 planets. The discovery of Gliese 581e, the smallest Earth-like extra-solar planet, is a giant step towards fulfilling the dream of finding other earths, other civilisations. Gliese 581e is not yet an Earth, but it represents staggering progress. The work carried out by this astronomer in the study of stars with orbiting planets earned him the very first Viktor Ambartsumian International Prize in 2010.
Since the discovery of Pegasus 51b, the first extra-solar planet that was “found” in 1995 by the Swiss Michel Mayor – who revolutionised the science of space and an entire theory solely based on the solar system – 700 planets have already been discovered. This knowledge leads to new questions, demands various insights, and opens the field of vision on the process of planetary formation, about which very little is still known. Nuno Santos notes, “We know more than we did in 1995, but there are still many unanswered questions. Knowing how planets are formed is interconnected with other questions. How many stars in the sky could have formed planets? How many stars might have Earth-like planets? And of these planets, how many are able to support life?” The answer to these questions, says Nuno, will help us answer yet other questions: how many civilisations could there be in the universe? Nuno Santos is convinced that we are not alone, but he refuses to come up with an image of what beings from other planets might be like. “We’re limited to imagining that which we know; it’s very difficult for us to think of something that is clearly different to us.”
While we are still far from knowing if there is life on other planets, we do nonetheless know of “the existence of rocky planets, but none of those discovered so far seems to have all the necessary conditions to support life. Those we know of are situated in a “habitable zone”, and we call them the super-Earths. We suspect that most of them are too big and that their atmosphere is too dense to support life. But then again, there is also no single answer to the question of what a habitable planet is,” explains Nuno Santos, who continues with more space enigmas: “For example, we don’t know exactly how water appeared on Earth. Was it brought by comets?”
If the Earth’s past remains shrouded in mystery, its future is not any clearer either. In light of what is known about the life of a star such as the Sun, it will become a red giant one day and swallow the Earth. Should this happen, Nuno reassures us with a smile, it will be a long time from now, in around five billion years’ time. The sun has hit midlife; it was formed from a cloud that collapsed due to gravity. In the course of that physical process, explains Nuno, a rotating disk of gas and dust is formed, and this gas and dust come together and give rise to planets. The Sun evolves very slowly, in an almost stable manner, and only when it runs out of the fuel that allows it to shine, will it die. This is what happens with all stars similar to the Sun, which is most of them.
The express to a habitable planet
The discovery of the planet Gliese 581e (1.9 times the Earth’s mass) was the result of more than four years of observations using the most successful low-mass extra-solar planet hunter in the world: the HARPS spectrograph attached to the ESO telescope in Chile. It is an instrument that makes it possible to detect planets with a significantly small mass, but which are still larger than Earth; that means it doesn’t have the range capability to find planets that can support life.
The ESPRESSO, the new detector that is currently being developed, will make it possible to go further, reaching new dimensions. “It is a much more sensitive instrument which, when coupled with VLT telescopes, will make it possible to detect planets that gravitate to Sun-like stars at just the right distance to allow for the existence of life. We will have this capability for the very first time, and we will carry it out most systematically,” explains Nuno. The instrument, which is in the final stages of design, will be built next year and is expected to start functioning in 2016 in Chile.
Nuno Santos, team leader of the Centre for Astrophysics of the University of Porto (CAUP), which coordinates the national component of the ESPRESSO consortium composed of four countries (Switzerland, Spain, Italy and Portugal – CAUP and the Science Faculty of the University of Lisbon), emphasises the excellence of the space science carried out in Portugal, which has an above average international impact. This is particularly visible in the area of planet hunting, but it is also relevant in other areas of astrophysics, which has a very active research community. A fact that becomes all the more important when you consider that thirty years ago there was no astrophysics in Portugal.
“Many people would tell me, if you want to do astronomy, you’ll have to go to NASA. It seemed like something very distant in the 1980s.” Nuno Santos cannot say exactly when, nor why this fixation with being an astronomer came about. “I’ve always liked astronomy, perhaps because I watched Carl Sagan documentaries. I liked other things too, usually something that was far removed in time and space. I could have been a palaeontologist and studied the origin of life or something that is distant and represents a mystery”.
If Nuno Santos had to go to NASA or elsewhere, he would. His fascination for astronomy is such that he gladly accepts such risks. And when he gives talks at schools and senses that the children listening are interested and in wonder of the existence of a universe to be explored, he makes it a point to let them know that you don’t need to be a genius in order to be an astronomer. “It’s important that children understand that. Someone who has a special interest in science, someone who wants to be an astronomer can be one, as is the case in any other profession.”
The thrill of discovery
The first time he observed space through a professional telescope, Nuno Santos was already studying Physics at university. In Chile, after pointing his telescope at a nebula, the craters of the moon or the rings of Saturn, he did not observe these through a little hole. The romantic view people usually have of astronomy has nothing to do with the daily life of an astronomer nowadays. Far away from the telescope, observation takes place on a computer screen. There is little observation time, but many hours of analysing data. “Science isn’t necessarily made up of beautiful images; the wonderment lies in the discovery,” notes Nuno.
He recalls the thrill of discovering the planet orbiting the star ara (mu Arae). Nuno Santos was co-leading a project into the study of stars, the objective of which was not to look for planets. But as the data came in, they began to see that there was something else there. Three months of gathering data went by before they reached a conclusion: they had discovered the smallest ever extra-solar planet found up until then, with around 10 times the mass of the Earth. “In 2004, this discovery represented an enormous leap in knowledge; it would be the first potentially rocky planet. It was an extraordinary process and months of great excitement. Every time a new piece of data arrived, a new measurement, the team would wonder, is it a planet or not? Until finally the announcement was made. At the same time, a North American team announced the discovery of other similar planets, which were just as important, but we managed to get there first. In short, there was all that healthy competition typical of science. It was exhilarating.”
Since 2007 Nuno Santos has been at Porto’s Centre for Astrophysics – the largest in Portugal – and heads a team of eight researchers and nine PhD students in this field. He also emphasises the collaboration of an amateur astronomer, some of whose observations are being published. A prospect that is possible nowadays, given the high level of technology that the market has to offer. “Anyone who has money to invest and chooses to buy a telescope and a camera, instead of a car, can carry out near-professional work. The distance between amateurism and professionalism is becoming increasingly smaller. When I was a teenager and started making some observations, most of the known comets had been discovered by amateurs. An amateur telescope lets you see more than you think.” And even if you don’t intend to gather scientific data, surely looking at the sky and pointing your telescope at a nebula, the craters of the moon or the rings of Saturn is an awe-inspiring experience.
By Ana Serpa