The iREx team is leading an international collaboration that is currently building an infrared spectrograph named NIRPS. This instrument, like the SPIRou spectrograph, will allow to detect exoplanets around the coldest stars. To do so, NIRPS will use the velocimetry method, also called the radial velocity method, one of the most efficient ways to detect and characterize new planetary systems.
In the last few years, the search for exoplanets has extend to stars that are differ significantly from our Sun. Red dwarfs, stars with a mass between 10 and 50% of that of the Sun, are really interesting. One of the main reason is because it is easier to detect temperate terrestrial planets, favorable to life as we know it, around these stars. However, as these objects are colder than our Sun, they emit most of their light in the infrared. It is thus in the infrared that we mush observe them to measure with a high precision their velocity and thus detect and characterize their planets.
The iREx team got a grant from the Canada Foundation for Innovation to build NIRPS. Its developpement is made by a large international collaboration that includes the Observatoire de Genève. The Observatoire de Genève team operates HARPS, one of the most productive radial velocity spectrographs for planet discoveries. The findings made with HARPS have revolutionized our comprehension of planetary systems. HARPS allows to measure radial velocity with a precision better than 1m/s (3.6 km/h), which is still the state-of-the art in the field.
NIRPS will be installed in 2021 at the 3.6-m La Silla telescope in Chile. This telescope is operated by ESO (European Southern Observatory), an organisation that operates various observatories in Chile, including the 4 giant telescopes of the VLT. It will be possible to use NIRPS in parallel with HARPS, which has already been running on the telescope for 10 years. NIRPS will extend the current capacity of HARPS in the infrared, which will give the teams that participate to the project unique capacity to follow-up and characterize planetary systems. Considering the important strategical importance of NIRPS, ESO will allocate 740 observing nights distributed over a 5 years period to the NIRPS team.
Artist rendition of the red dwarf Gliese 581 and its planetary system. This system, discovered with HARPS, has at least three planets. This star is one of the rare red dwarfs that are bright enough to be observed with HARPS. NIRPS will allow to study a much greater number of red dwarfs. Credits: ESO
NIRPS will be used for diffrerent projects related to the search for exoplanets. Here are the various research themes:
The majority of the stars in our solar neighborhood are red dwarfs, and we only know a few planets around these stars. NIRPS will be used to do a systematical survey of the red dwarfs that are closer to the Sun. This will allow to detect Earth-like planets in the temperate zone around these stars. As these red dwarfs are close to us, these planets could be among the firsts to be seen directly with the large telescopes that will be built, including TMT and E-ELT. The recent discovery of a terrestrial planet in the habitable zone of our closest neighbour, Proxima Centauri, suggests that we might find many comparable planets around other low-mass stars.
In 2018, NASA lauched a small satellite, TESS, which has the objective to detect exoplanets everywhere in the sky using the transit method. This satellite will identify planets that pass in front of their stars, but will not measure their masses. By measuring the effect the planet has on the movement of its star, NIRPS will allow to obtain a mass for these planets and therefore constrain their composition. The planets that are the more similar than the Earth will then be studied with NIRISS on James Webb Space Telescope.