Now there’s even more chance of finding alien life: Earth-like planets around small stars may have protective magnetic fields

  • Like Earth, these magnetic fields could protect the surface from radiation
  • Such planets are often tidally-locked, with same side always facing its star
  • The more tidal heating a planetary mantle has, the better it is at dissipating its heat, cooling the core, which in turn helps create the magnetic field
  • With the planet protected from radiation, there is a chance for life to thrive

By Ellie Zolfagharifard For Dailymail.com

Published: 17:05 EST, 29 September 2015 | Updated: 17:09 EST, 29 September 2015

In a boost to the search for alien life, scientists say that planets similar in size to our own may be more habitable than first thought.

They argue that Earth-like planets, which orbit dim stars, may have magnetic fields that can protect life on the surface, much like our own world.

The magnetic field, born from the cooling of the planet's interior, deflects the charged particles in stellar wind, protecting the atmosphere from being lost to space.

In a boost to the search for alien life, scientists say that planets similar in size to our own may be more habitable than first thought. They argue that Earth-like planets, which orbit dim stars, may have magnetic fields that can protect life on the surface, much like our own world

In a boost to the search for alien life, scientists say that planets similar in size to our own may be more habitable than first thought. They argue that Earth-like planets, which orbit dim stars, may have magnetic fields that can protect life on the surface, much like our own world

Planets orbiting near such small stars are easier for astronomers to target for study because when they transit, or pass in front of, their host star.

This blocks a larger fraction of the light than if they transited a more massive star.

But because such a star is small and dim, its habitable zone - where an orbiting planet gets the heat necessary to maintain life-friendly liquid water on the surface - also lies relatively close in.

And a planet so close to its star is subject to the star's powerful gravitational pull, which could cause it to become tidally locked, with the same side forever facing its host star, as the moon is with the Earth.

A planet that is tidally 'locked' to its star. As the planet orbits the star along the dotted line, the same side of the planet faces toward the star. The stick figure is standing at a point, where the star is always overhead. On the right, the graphic shows how one side is always day, while the other is always night
A planet that is tidally 'locked' to its star. As the planet orbits the star along the dotted line, the same side of the planet faces toward the star. The stick figure is standing at a point, where the star is always overhead. On the right, the graphic shows how one side is always day, while the other is always night

A planet that is tidally 'locked' to its star. As the planet orbits the star along the dotted line, the same side of the planet faces toward the star. The stick figure is standing at a point, where the star is always overhead. On the right, the graphic shows how one side is always day, while the other is always night

That same gravitational tug from the star also creates tidally generated heat inside the planet, or tidal heating. 

ARE ASTRONOMERS BEING FOOLED BY 'MIRAGE EARTHS'? 

Recently, scientists have suggested that the most abundant stars in our galaxy, red dwarfs,, might be able to host habitable planets.

But a new study has warned that any 'Earth-like' worlds we spot in the habitable zone of these stars will be nothing more than an illusion – owing to the intense radiation they receive early in their life.

The study claims that so-called 'mirage Earths' will look like our own planet from afar, but peering deeper into the planet will reveal it to be a barren world with no water, or life, on its surface.

The research was carried out by astronomy graduate student Rodrigo Luger and assistant professor Rory Barnes at the University of Washington. They studied red dwarfs, also known as M stars, which make up about 75 per cent of stars in our galaxy.

In their study the researchers found that, early in their life, M dwarfs were much more active. This is the same for most stars, but M dwarfs take longer because they are so much smaller.

This means that once planets have formed, roughly 10 million years after the star's formation, they will be subjected to the full brunt of the star's early activity until it quietens down.

Any water present on the planets would therefore be boiled by this intense heat from the sun.

In a paper published in the journal Astrobiology, lead author Peter Driscoll at Washington University attempted to determine the fate of such worlds across time.

'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?'

The research combined models of orbital interactions and heating.

Simulations ranged from one stellar mass - stars the size of our sun - down to about one-tenth of that size. 

Rory Barnes, assistant professor of astronomy, said there has been a general feeling in the astronomical community that tidally locked planets are unlikely to have protective magnetic fields 'and therefore are completely at the mercy of their star.'

This research suggests that assumption false.

Far from being harmful to a planet's magnetic field, tidal heating can actually help it along - and in doing so also help the chance for finding life on the surface.

The more tidal heating a planetary mantle experiences, the better it is at dissipating its heat, thereby cooling the core, which in turn helps create the magnetic field.

Barnes said that in computer simulations they were able to generate magnetic fields for the lifetimes of these planets.

In most cases. 'I was excited to see that tidal heating can actually save a planet in the sense that it allows cooling of the core. That's the dominant way to form magnetic fields,' he said.

And since small or low mass stars are particularly active early in their lives - for the first few billion years or so — 'magnetic fields can exist precisely when life needs them the most.' 

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