14 DAY TRIAL // Investigators at the Pierre Simon Laplace Institute in Paris, led by planetary scientist Jérémy Leconte, recently published a new study that manages to refine the inner limits of the habitable zone around the Sun. This zone is represented by the distance ranges where liquid water is possible in the solar system.
Every star has a habitable zone, a region where temperatures are neither too hot, nor too cold to support liquid water on the surface of a planet within it. In our solar system, Earth lies right at the center of the Sun's so-called Goldilocks zone.
What the new research suggests is that our world may have suffered a devastating greenhouse effect over the course of its 4.5-billion-year history, were it located just a bit closer to the Sun. The study provides new measurements for the inner edge of the Goldilocks zone.
One of the most significant implications associated with this study is the fact that it drastically reduces the number of potential Earth-like planets that may support liquid water on their surfaces outside the solar system. However, there is some criticism to the new model as well.
For example, some researchers say that its conclusions are too restrictive, primarily because the dataset can only be applied to planets very similar to our own. These worlds also have to feature abundant amounts of liquid water on their surface, which is unlikely to be a very common occurrence.
Leconte and his team determined that the amount of water on Earth would lead to a runaway greenhouse effect if our world received just 10 percent more solar radiation than it does today. Under such circumstances, water vapors in the atmosphere would trap massive amounts of heat.
This process would lead to further evaporation, which would in turn contribute to even more warming. This vicious cycle would accelerate and propagate until all the world's oceans would disappear, Nature reports.
Critics to this research say that water vapor may indeed be a danger for Earth, but not for other worlds, where such high amounts of surface water are unlikely to exist. Even for exoplanets very similar to our own, triggering a runaway greenhouse effect would be very difficult.
Studying habitable zones is a very complex process. No two stars are identical, meaning that all habitable zones in the Cosmos have different properties. The same thing goes for the planets that occupy these orbits. This is probably why detecting an Earth-analog world is like looking for a needle in a haystack.