by A glimpse into the future for free, exoplanet science suggests what is to come Extra Large European Telescope (ELT) to give us the best chance in the next two decades to detect nearby biosignals rocky world orbiting other stars. That’s the conclusion of a new study that simulated what it will take to characterize life outside our solar system with the faint prospect of host life, such as Proxima Centauri b.
This study will allow astronomers to set their sights on key exoplanetary targets during the 2030s and beyond.
In addition to measuring the bulk planetary properties of exoplanets — mass, radius and orbital period — astronomers learn about these exoplanets by studying their atmospheres. The IS James Webb Space Telescope (JWST) it does this through transit spectroscopy, for example. As a planet moves past (in other words, moves in front of) its star in the telescope’s field of view, some of the starlight filters through the planet’s atmosphere. Any atmospheric molecules in that atmosphere can absorb starlight. Importantly, different molecules absorb at certain wavelengths, making each wavelength a unique molecular signature. This is how the JWST recently found hints of methane and carbon dioxide in the the atmosphere of the exoplanet K2-18bfor example.
Related: Machine learning could help find alien technology. This is how
However, our machines only manage to see a small fraction of the planets transiting their stars, which means that scientists have to use another method to characterize exoplanetary atmospheres. That includes worlds that do not transit at all, as well as worlds that may be transiting without us noticing.
Direct imaging is one option, but imaging exoplanets directly is a tough proposition.
Although many exoplanets have been imaged to date, as HD 950086b, they are all young, big life still hot from their formation process. They therefore glow brightly in infrared light at large angular separations from their parent star. That is to say, we cannot see any details about these worlds – the planets are visible only as principles of light – but within their light patterns are hidden absorption lines associated with the molecules of the atmosphere. To tease out this spectral data, however, requires a very large telescope to obtain a high enough signal-to-noise ratio of the planet’s light and background data.
So, with a trio of massive ground-based observatories set to appear for the first time in the next decade, astronomers Huihao Zhang, Ji Wang and Michael Plummer, all from Ohio State University, wanted to test how well they would be characterized by the eyes that are to come upon the earth. exoplanets by direct imaging. The goal was to see how much better they do the task when compared to transit spectroscopy performed through JWST’s 6.5-meter (21-foot) mirror.
The three next-generation ground-based telescopes are the 39-meter (128-foot) European Extremely Large Telescope (ELT), the 98-foot Thirty-Meter Telescope (TMT) on Mauna Kea and the 24-meter (79 feet) Magellan giant telescope (GMT). The ELT and GMT are being taken at specific locations in Chile’s Atacama Desert; just last December the first mirror items for the ELT were shipped to South America.
“It’s hard to say whether space telescopes are better than ground-based telescopes, because they are different,” Zhang said. press release. “They have different environments, different places, and their opinions have different impacts.”
Zhang, Wang and Plummer simulated the performance of two instruments on the ELT — the Mid-Infrared ELT Imager and Spectrometer (METIS) and the High-Angle Monolithic and Near-Infrared (HARMONI) field spectrograph. They modeled these tools on 10 real-life exoplanets orbiting nearby red ox stars, testing how well they can detect potential biomarkers such as molecular oxygen, carbon dioxide, methane and water through direct imaging.
“Not all planets are suitable for direct imaging,” Zhang said. “But that is why simulations give us a rough idea of what the ELT would deliver and the promises they intend to hold when they are built.”
The results were mixed. A world called GJ 887bwhich Super Earth is four times more massive than our planet which orbits the brightest red dwarf in our sky 11 light years away, is best done in the simulations. METIS in particular proved capable of detecting the aforementioned bio-indicator gases in its atmosphere. In the simulations, METIS could detect the same biosignatures on exoplanets Proxima b and Wolf 1061c, while HARMONI was able to make the same detections but needed longer exposure times to do so.
However, the ELT is likely to struggle in trying to directly image and characterize the seven worlds of the TRAPPIST-1 system, says the team, due to “atmosphere view limits” hinder efforts to resolve key measurements of tiny angular separation of the planet from its star. In this case, the transit spectroscopy of the JWST does better here, but even the $10 billion dollar observatory is struggling.
Preliminary results from the JWST indicate that the innermost planets of TRAPPIST-1, worlds b and c, do not have atmospheres. It may take years for the JWST to collect enough data to infer the other five TRAPPIST-1 worlds, including planets d, e and fa, that are inhabited by Earth. habitable zone.
The capabilities and limitations of the ELT and the JWST will not be the final word on exoplanet characterization. The latest one a ten year survey for astronomy from the National Academy of Science recommended the development of a new, a giant space telescope with a mirror of at least eight meters to accelerate towards a launch date in the 2040s. Such a telescope would be optimized to detect, image and characterize rocky worlds in habitable zones around nearby stars, including Proxima b.
Related Stories:
— It might be easier to detect alien life if we are looking for ‘Jurassic life.’ Here’s why
— The world spews ‘biosignals’ into space, suggesting that other worlds with lives may do the same
— Extraterrestrial life could exist in the coldest depths of space, Ryugu asteroid samples reveal
Until then, Zhang, Wang and Plummer believe that the next generation of large ground-based telescopes, and the JWST, can encourage astronomers to start exploring exoplanets and begin to learn whether some of them might support the life really – as we know it, at least.
Their results were published in December 2023 i The Astronomical Journal.
