In the previous article (linked above), we discovered what light is. Today, we will apply that and discover other technologies that have helped the search for life on other planets. 

First, we must understand the search for life in a broader context through the Fermi Paradox, which states that if there is a mathematically high likelihood for life on other planets, why haven’t we found conclusive evidence? This question is answered using technology and physics like telescopes and spectroscopy.

Telescopes are humanity’s primary tool for exploring the universe, allowing astronomers to observe distant stars and planets. Over time, advancements in telescope technology have expanded our ability to detect and study exoplanets – planets beyond our solar system. There are two main types of telescopes used in this search: Optical telescopes capture visible light from celestial objects, helping astronomers identify planetary systems. Infrared telescopes, like the James Webb Space Telescope (JWST), can peer through cosmic dust and detect heat signatures, making them crucial for studying planetary atmospheres. One of the most effective methods for discovering exoplanets is the transit method, used by space telescopes like Kepler and TESS. When a planet passes in front of its star, it temporarily dims the star’s light. By analyzing these dips in brightness, astronomers can infer a planet’s size, orbit, and even atmospheric composition. However, finding a planet is only the first step. The next challenge is determining whether it could support life.

To determine whether or not a planet can support life, physicists determine if the planet lies in a habitable zone. Physicists first find the star’s luminosity to determine the size of a star’s habitable zone. Using the equation, L = 4πr²σT⁴, where r = radius of the star, σ = Stefan – Boltzman constant which defines the amount of energy emitted by a blackbody per area, and T = star’s temperature. The habitable zone is where a planet can have liquid water on its surface without boiling or freezing, thus allowing it to support carbon-based life forms. This “goldilocks” zone depends on the planet’s distance from the sun. Because luminosity decreases with distance and depends on the star’s size and temperature, luminosity is a way to determine the distance and habitable zone size. For example, bigger, hotter stars have a habitable zone that is further than stars that are small and colder.

Astronomers use this information to narrow their search and use technology like spectroscopy to discover more about planets in habitable zones. When light from a star passes through its outer layers, specific wavelengths are absorbed by elements in the stellar atmosphere, creating a unique absorption spectrum – like a code. This allows astronomers to determine the star’s chemical composition.

Every day, these technologies bring us closer to answering the question: Are we alone in the universe?