(Image credit: Swinburne Astronomy Productions/ESO)
The Extremely Large Telescope (ELT), currently under construction in northern Chile, will provide the ability to study the Milky Way in greater detail than any previous ground-based telescope.
It’s hard to overstate its potential impact. The ELT’s main mirror array will have an effective diameter of 39 meters. It will collect significantly more light than its predecessors, and will be able to provide images 16 times sharper than those of the Hubble Space Telescope. It is expected to launch in 2028, and results could be available almost instantly, as a recent study has shown.
One of the most exciting capabilities of the ELT will be its ability to capture faint atmospheric spectra of exoplanets. This typically happens when a planet passes in front of its star from our perspective. A small fraction of the starlight passes through the planet’s atmosphere to reach us, and by analyzing the absorption spectra, we can identify molecules present in the planet’s atmosphere, such as water, carbon dioxide, and oxygen. The James Webb Space Telescope (JWST) has already collected data on several exoplanet atmospheres, for example.
However, sometimes the transit data we can collect may not be strong enough. For example, when JWST examined the atmospheres of the planets in the TRAPPIST-1 system, planets b and c appeared to have no atmosphere, but the data were not strong enough to rule out their presence. There may be thin atmospheres with spectral lines that are too weak for JWST to observe. The increased sensitivity of the ELT should help resolve this uncertainty.
Even more exciting is that the ELT will be able to collect spectra not only of exoplanets transiting their star, but also of those that do not, using reflected starlight.
To assess the power of the ELT, the new study modeled the results for a variety of scenarios. The researchers focused on planets orbiting nearby red dwarf stars, as these are the most common types of exoplanets, and considered four test cases: a non-industrial Earth with plenty of water and photosynthetic plants; an early Archean Earth where life is just beginning to evolve; an Earth-like world where the oceans have evaporated, reminiscent of Mars or Venus; and a prebiotic Earth capable of supporting life but without it. For comparison, the team also looked at Neptune-sized worlds, which should have a much thicker atmosphere.
The goal was to find out whether the ELT could distinguish between different Earth-like worlds, and more importantly, whether the data could mislead us by giving false positives or negatives. That is, whether a dead world would look like a living world, and a living world would look like a barren one.
Based on their simulations, the authors conclude that we should be able to make clear and precise distinctions for nearby star systems. For the nearest star, Proxima Centauri, we could detect life on an Earth-like world in just ten hours of observations. For a Neptune-sized world, the ELT would be able to capture planetary spectra in about an hour.
So if life exists in a nearby star system, the ELT looks set to detect it. The answer to perhaps the most important question in human history could be found in just a few years.
The original version of this article was published on Universe Today.
Brian KoberleinSocial Link NavigationAstrophysicist and Author
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