Brazilian university develops exoplanet hunter – 7/8/2023 – Science

A new exoplanet hunter instrument developed with important Brazilian participation has just started operating at the La Silla observatory, in Chile.

The researchers hope the equipment can discover and characterize many distant worlds, and perhaps even detect biosignatures — evidence of life — in the composition of their atmospheres.

The Nirps project (acronym for Near InfraRed Planet Searcher, or “near infrared planet searcher”) began to be conceived in 2014, to meet a demand from the ESO (European Southern Observatory), the largest astronomical research body in the world. , which launched a call for proposals for new instruments for the NTT telescope, operated in La Silla.

It was there, by the way, that the hunt for exoplanets reached a great degree of maturity, with a good part of its observation time dedicated to the activity, under the coordination of the team of Michel Mayor (awarded the Nobel Prize in 2019 for the discovery of the first exoplanet to orbit around a Sun-like star in 1995).

The technique used to detect exoplanets there is gravitational wobbling (technically known as radial velocity variation detection). In short, it measures how much a star wobbles back and forth as it is gravitationally attracted by planets revolving around it. This is done using spectrographs, equipment that decomposes light into its component colors and records this signature.

Nirps is the newest of these spectrographs, and its genesis is at the Federal University of Rio Grande do Norte (UFRN), under the coordination of astronomer Bernard Delabre, from ESO, then a visiting engineer, and with the local leadership of astronomer José Renan de Medeiros. “It was here that we started the optical design of the instrument”, says the Brazilian researcher.

When the project was born, there were great expectations for Brazil to become the first non-European country to join the ESO consortium. The Brazilian government had signed an agreement with the organization in 2010, but high costs held up ratification for years.

When the project was finally approved by Congress, in 2015, it was merely a “bombshell” for the administration of Dilma Rousseff (PT), who could not pay the costs. To date, the agreement has not been sanctioned by the Presidency so that it could enter into force.

“The initial idea was to build Nirps in Brazil”, says Medeiros. “Unfortunately, the lack of definition of the Brazil-ESO agreement made it impossible to build the instrument here at UFRN.”

Instead, Medeiros and Claudio Melo (an astronomer from Rio Grande do Norte working directly at ESO) pursued international partnerships. In 2017, they then formed a consortium with universities in Canada and Europe, in addition to UFRN itself.

“Six years later, the result is there: Nirps has been built and is in operation at ESO’s 3.6-metre telescope in La Silla”, says Medeiros.

playing in pairs

One of the most interesting aspects of Nirps is that it will work much of the time in partnership with Harps, another spectrograph at La Silla and responsible for discovering many exoplanets since 2003.

Harps operates on visible light observation; Nirps, on the other hand, will work with infrared, “which will make it possible to observe a much larger number of stars”, stresses Medeiros.

The ambition is that the new instrument —completely dedicated to the study of exoplanets— achieves sufficient precision to measure variations in velocity in the swaying stars of 1 m/s.

However, it is enough to focus on rocky planets like ours frequenting the so-called habitable zone of stars much smaller, cooler and more common than the Sun, the so-called red dwarfs.

The habitable zone is the region around a star whose radiation incidence allows a terrestrial planet to maintain liquid water stably on its surface —an essential condition for life (at least in the forms we know).

Put another way, it’s the “not too hot, not too cold” band around a star. For Earth, being in the habitable zone means having a relatively long orbit, which the planet takes 365 days to traverse. As for planets around red dwarfs, a typical orbital period for a planet in the habitable zone would be a few weeks at most. The more modest orbit implies a greater radial velocity variation, which facilitates detection.

The construction of Nirps cost around 10 million euros (R$ 52.7 million), 60% funded by the universities of Montreal and Geneva, and its initial useful life is estimated at a decade.

Instrument could be used to search for life on exoplanets

The most exciting aspect of Nirps’ development is the prospect that it will serve to try to detect signs of biological activity on one of these exoplanets.

The idea is to use the spectrograph to capture the light coming from the star and skimming through the planet’s atmosphere as it makes a transit in front of it. The luminous signature, therefore, would carry signs of the composition of the molecules that it encountered along the way.

“Nirps will have a great asset, programmed for the second or third year of operations, which is the use of a laser frequency comb, being developed by the consortium itself”, reveals Medeiros. “This will offer the possibility to reach accuracies that until now have not been achieved by other instruments.”

According to him, the opportunity for continued observation and the use of the laser frequency comb should provide the level of sensitivity expected for an effective search for biosignatures, especially for complex molecules (which could only be produced by life, and not by other processes). geological).

And the most exciting thing is that Brazilian researchers will have priority access to the data and will work on discoveries made by the consortium responsible for the instrument. “It is the first time that Brazil participates in the construction of a cutting-edge instrument for ESO and the first time that a Brazilian team participates in a program with guaranteed telescope time dedicated to the search for exoplanets”, highlights the researcher from UFRN.