What observations might the Extremely Large Telescope make of Proxima Centauri’s planet?

Proxima Centauri B, the exoplanet closest to Earth, resides within the habitable zone of a red dwarf star just 4 light-years away. With a mass similar to that of Earth, it receives approximately 65% of the energy Earth receives from the sun. Depending on its evolutionary history, this exoplanet could potentially possess water-filled oceans and an oxygen-rich atmosphere.

While Proxima Centauri B holds the potential to harbor life, it could also be a barren celestial body. Nevertheless, it remains an exceptional target in the quest for extraterrestrial life. However, there is a significant obstacle in our pursuit. The conventional methods we employ to detect biosignatures are ineffective when it comes to Proxima Centauri B.Typically, exoplanets are discovered through the transit method, which involves the regular passage of a planet in front of its star from our vantage point. This results in a recurring decrease in the star’s brightness, providing evidence of the planet’s existence. In the case of transiting exoplanets, we can analyze the changes in the star’s spectrum during these transits.

When starlight traverses an exoplanet’s atmosphere, certain wavelengths are absorbed by the gases present. By examining the absorption pattern, we can identify different molecules and their presence, such as water and carbon dioxide, within exoplanet atmospheres.However, Proxima Centauri B does not transit its star. Its discovery was made using a different technique called Doppler spectroscopy. By observing the light emitted by Proxima Centauri, we can detect slight redshifts and blueshifts in its spectrum over time. This occurs due to the gravitational influence of Proxima Centauri B, causing a slight wobble in the star. Consequently, we have knowledge of the exoplanet’s existence, as well as a reasonable estimation of its size and mass. However, the absence of transits prevents us from observing its atmospheric absorption spectrum.

However, a recent study published on the arXiv preprint server proposes an alternative method to detect signs of life. Instead of searching for light that passes through the planet’s atmosphere, the study suggests looking for light that has bounced off the planet’s surface. This approach has been successfully applied to planets like Mars and the outer planets, which do not cross in front of their host star. Therefore, it is feasible to employ this technique for exoplanets as well.

The issue lies in the fact that the reflected starlight from a planet is minuscule in comparison to the brightness of the star itself. Detecting the faint light of a planet is akin to capturing the glow of a firefly fluttering near the periphery of a spotlight. To overcome this challenge, astronomers have utilized masks to block out the intense radiance of a star and observe its planetary system. This technique has been successful in directly observing large gas planets orbiting other stars, but it has not yet been effective in detecting Earth-sized worlds.

In this study, the researchers focus on the potential of the Extremely Large Telescope (ELT), which is currently being constructed in Northern Chile. Specifically, they investigate the capabilities of the High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI), which will enable the capture of high-resolution spectra using the ELT. The team conducted simulations using the masking technique to capture the light emitted by an exoplanet orbiting Proxima Centauri. The question at hand is whether HARMONI can gather enough high-resolution data to identify biogenic molecules.

Their findings indicate that, as it stands, HARMONI’s proposed mask configuration is too large and would obstruct a significant portion of the exoplanet’s light. However, the researchers also discovered that with certain modifications, it would be possible to study the atmosphere of Proxima Centauri B. Simply reducing the size of the mask is not a viable solution, as it would allow more starlight to reach the ELT, thereby overwhelming the exoplanet data. Instead, the team suggests conducting detailed simulations to optimize a design specifically tailored for studying Proxima Centauri B.

Implementing these modifications would not be a simple or inexpensive task, but the potential rewards make it a worthwhile endeavor. Proxima Centauri B, our closest known exoplanet, holds a prominent position on the list of celestial bodies we intend to explore as we venture beyond our solar system. If it were to harbor life, it would undoubtedly be at the forefront of our exploration priorities.

This article is republished from PhysORG under a Creative Commons license. Read the original article.