‘Earth-like’ exoplanets may exist—but we don’t know of any yet
Claiming an exoplanet to be “Earth-like” is a trend that needs to bite the dust
Despite the widespread use of the term "Earth-like" when describing exoplanets, it is crucial to note that no such planets have been definitively identified thus far. While astronomers have discovered over 6,300 exoplanets to date, many of them possess peculiar characteristics that make them difficult to comprehend. Early discoveries revealed planets shrouded in radiation around pulsars, while others orbit their stars at incredibly close or distant distances, challenging our understanding of their formation and evolution.
Among these diverse exoplanets are both rocky worlds with scorching temperatures that melt lead and frigid ones locked in solid ice. The search for a planet resembling Earth is undoubtedly emotionally charged, as such a discovery would provide profound insights into the origins of life and our own existence. However, the term "Earth-like" has been misapplied frequently, as it only signifies that a planet is of comparable size or mass to Earth.
This designation fails to capture the full complexity of a planet's characteristics, such as its atmospheric composition, surface gravity, and distance from its host star—factors that greatly influence a planet's temperature and habitability. For instance, Venus, which is only slightly smaller and less massive than Earth, has a runaway greenhouse effect that renders its surface uninhabitable. Thus, even if an exoplanet shares Earth's size, it may not be truly "Earth-like."
The latest candidate in the race to find an Earth twin is LHS 1140b, located approximately 49 light-years from our solar system. Discovered in 2017 by the MEarth project, this exoplanet shares Earth's density and composition, giving it a similar surface. Although it resides within its star's habitable zone, LHS 1140b is likely far colder than Earth and experiences a stronger gravitational pull. Consequently, it is unlikely to support life as we know it.
The persistent use of "Earth-like" to describe exoplanets is misleading and should be abandoned, as it fails to accurately represent the vast diversity and complexity of these distant worlds.
Written by urgent.news from Scientific American's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
