Even Goldilocks planets need a well-behaved star

There are about 4000 planets that have been so far discovered around other stars in the universe. Some of them even have the right distance to size ratio to make liquid water possible. But here's why you shouldn't pack your bags just yet.

Life is possible on Earth because it was placed at just the right distance from our Sun and is of just the right size. This allows for temperatures on our planet to be just right for water to not evaporate into space.

Out of the 4000 exoplanets so far discovered around stars, some have gained attention recently as having the right distace to size relationship with their parent stars as well. These planets are not at the same distance from their parent star and not the same size as our Earth, but it's the ratio that is been considered. These include Ross, Proxima, and TRAPPIST. There has been a lot of excitement about the TRAPPIST system recently, because there are several planets in that solar system that have the right size to distance ratio for possibility of liquid water.

But astrophysicists at Rice University are now looking into another factor that would effect any likelihood of liquid water. The space weather factor.

Stars in space are really violent furnaces. They churn out tremendous amounts of electromagnetic radiation. This radiation is blown into space by what is known as solar wind. That's what allows them to heat planets at such long distances. Our Sun is an extremely violent star too. The reason we are not obliterated by such strong electromagnetic radiation is that most of that high-energy radiation and charged particles are deflected or absorbed before reaching the surface by layers of protection: the Sun’s output spreads out with distance, reducing its intensity; Earth’s magnetic field channels and traps charged particles in the magnetosphere; and our atmosphere absorbs and scatters harmful ultraviolet and X‑ray radiation, so only a fraction of the Sun’s raw energy reaches the ground where life can persist.

On planets around other stars, intense stellar flares and persistent stellar winds can strip away an exoplanet’s atmosphere or chemically alter it, removing or destroying the gases that enable surface liquid water. High-energy particles and X‑ray/UV radiation drive atmospheric escape, break apart water molecules and other volatiles, and change surface chemistry—especially for planets orbiting close to active stars or lacking a strong magnetic field. Conversely, moderate stellar activity can supply energy for prebiotic chemistry or help sustain a secondary atmosphere through sputtering and photochemistry. So whether an exoplanet can hold onto the pressure and composition needed for stable liquid water depends not only on its orbit and composition, but also on the star’s activity history, the planet’s magnetic protection, and how quickly atmospheric loss processes operate relative to replenishment mechanisms.