Right from the start, since far-off Antiquity, astronomy has always been a science based on observation. Although the theoretical description of astrophysical objects is an important aspect of this field, these efforts are meaningful only insofar as they can be confirmed by observations.
The study of exoplanets is no exception to this rule. In fact this field did not really take off until the discovery of the 1st exoplanets in 1992 (around a pulsar) and 1995 (around a star). Today, various methods make it possible to detect exoplanets directly and indirectly. The Institute’s researchers use a number of techniques:
- High-contrast imaging: Adaptive optics systems let researchers get a direct image of an exoplanet near its star. With current technology it is possible only to detect very massive planets, a few tens of million years old.
- High-precision infrared velocimetry: The velocimetry method, that allowed the discovery of several hundreds exoplanets, can be used to detect exoplanets around the coldest stars, if carried in the infrared with specialized spectrographs.
- Young stars: The study of young stars is closely linked to the study of exoplanets. Shortly after they are formed, exoplanets emit infrared light and can be detected much more easily than in old solar systems like ours. In addition, when observing younger stars we can see gas and dust that will give birth to new planetary systems within a few million years.
- Brown dwarfs: These are the missing links between low-mass stars (at least 7% of the Sun’s mass) and the most massive planets (no more than 1.3% of the Sun’s mass). They share many characteristics with massive planets, and are easier to study directly than exoplanets because many of them are located in the Sun’s immediate neighbourhood, and are not generally next to a host star.
- White dwarfs: These represent the last phase in the life of a star like our Sun. Researchers at the Université de Montréal have been studying white dwarfs since the 1970s. It was only recently that they found that the odd chemical composition of some of them can be explained by the accretion of materials from exoplanets. The study of white dwarfs opens the door to better understanding of the internal composition of Earth-like planets. No other known method can be used to directly measure the internal chemical make-up of an exoplanet.