New research indicates that exoplanets orbiting smaller stars may also present magnetic fields that are effectively shielding them from stellar radiation, thus making them hospitable to life.
These exoplanets, similar to our home planet may be hosting conditions perfect for the development of alien life. The research, combining models of orbital interaction observed between small stars and the planets orbiting stars found that the currently held assumption according to which tidal heating diminishes the chances of life forming on an exoplanet is not quite right.
The research, led by Peter Driscoll and published in the Astrobiology journal aimed at having a deeper insight on what happens to exoplanets over time as they are tidally locked to stars of different sizes.
The magnetic field of a planet forms as the core of this planet is getting cooler. Previous studies on magnetic fields have pinpointed that they are effectively fending off stellar radiation, maintaining the cooler temperature of the surface and protecting life forms while doing so.
Low-mass stars, also known as M-stars are a fairly common occurrence in the universe. As such, planets which are orbiting M-stars are also quite common. And not surprisingly, they’re a popular research target for astronomers as they are easier to detect when they transit the stars.
However, there is a danger hidden in this interaction. Low-mass stars are dim. As a result, the habitable zone created by such a star lies rather close to it. For the planet orbiting the star, a habitable zone translates into those points in space where heat emitted by the star is sufficient to keep liquid water on the surface liquid.
But when the habitable zone is so close to the star, it’s possible that the gravitational pull becomes so strong that the planet gets tidally locked to the star, meaning it will only show one side permanently. That is what happens to our Moon.
It is these exoplanets that interested the researchers in this case.
“The question I wanted to ask is, around these small stars, where people are going to look for planets, are these planets going to be roasted by gravitational tides?”,
stated Driscoll, who is a geophysicist at the Carnegie Institution for Science, Washington.
Together with Rory Barnes, who is an astronomy professor with the University of Washington, they looked at forces at play in the case of these celestial bodies, including tidal heating as a result of the gravitational pull exerted on the planets.
Typically, it is believed that planets which get tidally locked may not develop magnetic fields to protect them from radiation. In fact, according to the models that the scientists run, tidal heating is in fact a factor that may help create the magnetic field on the long run.
It may be counterintuitive, but what the scientists have found is that with more tidal heating the ability of a planet’s mantle to dissipate the heat increases. As a result, the core is cooled and the magnetic field gets stronger.
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