Cold stars with strong magnetic fields can have stellar winds strong enough to destroy the atmospheres of orbiting planets, making these worlds uninhabitable. The discovery is the result of simulations by scientists at the Leibniz Institute for Astrophysics (AIP) in Potsdam and could be crucial in the search for extrasolar planets or exoplanets that could support life elsewhere in the universe.

Researchers have discovered that certain charged particles that make up the stellar winds of magnetically very cold stars can reach five times the average speed of our Sun’s solar wind, which is falling at about 1.6 million kilometers per hour. This means that the exoplanets surrounding these stars can be bombarded by streams of charged particles moving at 5 million miles per hour (8 million kilometers per hour).

For context, that’s about 6,000 times the speed of a bullet fired from a gun, and enough to destroy the conditions necessary to support life on any planet that may be orbiting these stars, including worlds that fall into the so-called habitable zones. This is quite impressive as habitable zones are defined as those where the temperature is just right to host liquid water and therefore potentially support life as we know it.

Even cool stars can be hostile to life

According to the researchers, “cold stars” include stellar bodies divided into four categories: F-type, G-type, K-type, and M-type. These categories depend on size, temperature, and brightness.

For example, the Sun is an average star and is an example of a G-type star that is larger and brighter than F-type stars. Stars that are smaller and cooler than the Sun are M-types and are also known as “red dwarfs”. . These faint stellar bodies are the most common stars in the Milky Way, but are difficult to see due to their low luminosity.

In addition to light, stars emit a stellar wind. These winds of charged particles inevitably interact with the rotating planets.

An example of such an interaction is the aurora borealis created over Earth’s north and south poles. When solar winds collide with our planet’s magnetic bubble, the magnetosphere, several processes occur that result in glowing green patterns in the sky. But the result of the antics of the stellar wind, as it turns out, is not always so good.

While it is relatively easy to study the solar wind, humanity could place a spacecraft like the Solar Orbiter around our star and study the charged particles emitted from it, but directly seeing the stellar wind emanating from more distant stars is nearly impossible. .

Although astronomers can observe the effects of these stellar winds on the thin, thin gas that exists among the stars in the Milky Way to gain some insight, this method is only applicable to a few stars.

That’s why scientists are turning to numerical simulations and computer models to better understand the stellar wind without requiring direct observation, as in a recent study.

Working with the supercomputing facilities of AIP and Leibniz Rechenzentrum (LRZ), a research team has developed a complex model based on the properties of 21 well-observed stars. This was the first systematic study of the stellar winds associated with each of the above stellar categories.

This model allowed the scientists to predict how stellar properties such as gravity, magnetic field strength and rotational periods affect the speed of stellar winds. It also helped them estimate the expected size of the boundary between a star’s corona (outer atmosphere) and the stellar wind, called the Alfén surface. This helped determine whether planets orbiting the star occasionally slammed into the Alfvén surface or were completely embedded in the Alfvén surface, which could cause intense magnetic interactions between the planet and its parent star.