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What new methods can be employed to help astronomers distinguish the light from an exoplanet and its host star so the former’s atmosphere can be better explored? This is what a recent study accepted to Astronomy & Astrophysics hopes to address as an international team of researchers investigated how a novel and proposed telescopic instrument that could be capable of characterizing exoplanet atmospheres in new and exciting ways. This study has the potential to help scientists develop novel tools for examining exoplanets and whether they could possess life as we know it, or even as we don’t know it.
For the study, the researchers discussed how RISTRETTO, which is a proposed visitor instrument for the European Southern Observatory's (ESO) Very Large Telescope (VLT) and high-resolution spectrograph, could be used to analyze the atmosphere of Proxima b, which is the closest exoplanet to Earth and a rocky world that orbits within its star’s habitable zone. Using a series of computer models, the researchers created simulations designed to mimic real-world observations of Proxima b, including the separation of the planet’s signal from that of its host star.
In the end, the researchers found that RISTRETTO could potentially detect Proxima b from its host star, along with potentially requiring only 55 hours of observation time to make this detection and potentially detect oxygen and water within the planet’s atmosphere in 85 hours of observation time.
The study concludes by stating, “Looking forward, this work provides a foundational methodology for detecting and characterizing exoplanets in reflected light around nearby stars with ground-based telescopes. The RISTRETTO instrument concept and the data analysis techniques developed here pave the way for next-generation instruments on extremely large telescopes such as ELT-ANDES [Extremely Large Telescope- ArmazoNes high Dispersion Echelle Spectrograph] and ELT-PCS [Extremely Large Telescope-Planetary Camera and Spectrograph].”
Discovered in August 2016, Proxima b is located approximately 4.2 light-years from Earth and orbits the star Proxima Centauri (officially called Alpha Centauri C) as part of the triple-star Alpha Centauri system. While it orbits its star in just over 11 days, it is estimated to orbit in the middle of its star’s habitable zone and is hypothesized to be a terrestrial (rocky) world slightly more massive than Earth. Since Proxima b’s atmosphere is poorly understood, this could present an instrument like RISTRETTO an ideal opportunity to constrain the planet’s atmospheric characteristics and determine if it’s suitable for life. One of the caveats is its star has been observed to exhibit extreme solar activity, meaning it constantly bombards Proxima b with radiation, potentially stripping the planet of any atmosphere it might try to maintain.
While this study discusses the potential capabilities of RISTRETTO, a 2020 study first presented this groundbreaking instrument as potentially revolutionizing exoplanetary science. This was followed by a 2022 study that further examined RISTRETTO’s potential capabilities, most notably how it could be used to study Uranus, Neptune, and icy moons throughout the solar system. As noted, RISTRETTO is designated as a “visitor” instrument, meaning that it was designed and developed by a third party and temporarily installed on a larger instrument.
Along with Proxima b, other exoplanets within that system include Proxima c and Proxima d, with the official confirmation of Proxima c currently being debated. While Proxima b orbits within its star’s habitable zone, Proxima d is estimated to orbit within the interior edge of the habitable zone, similar to how Venus orbits within the interior edge of our Sun’s habitable zone.
How will RISTRETTO help astronomers better understand exoplanets and their atmospheres in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
