Researchers Say Tides Can Cut Life Short On Planets Orbiting Smaller Stars

Nov 27, 2008
Artist's impression of the planetary system around the red dwarf Gliese 581. The five Earth-mass planet in the foreground, Gliese 581 c, is just inside the habitable zone. (European Space Agency)

(PhysOrg.com) -- Planet hunters searching for planets suitable for life will likely find them first around low-mass stars because it's technically easier than finding such planets around hotter, more massive stars, researchers predict.

But Earth-like planets around stars smaller than our sun won't be liveable for long, according to a study led by Rory Barnes, a research associate with The University of Arizona's Lunar and Planetary Laboratory. Such planets can face "tidal extinction" within about a billion years.

A star only a quarter-to-a-tenth as massive as our sun is also cooler than our sun, so the "habitable zone" for its planets – where water is liquid – also will be closer in, Barnes said.

"This close proximity results in accelerated tidal evolution," Barnes said. "Tides will be so powerful that the Earth-like planet's orbit will shrink. In some cases, orbits can shrink so much and so quickly that the planet may pulled through the inner edge of the habitable zone in less than a billion years, and all the planet's water will boil away."

If habitable planets around low-mass stars are massive enough and, say, have more circular, less eccentric orbits, they could last 4.5 billion years – the age of the Earth – before the star's tidal forces tugs them closer in to roast.

"Planet hunters may detect planets in habitable zones that are doomed to become uninhabitable in the future," Barnes said. "Alternatively, they may find planets today that were liveable in the past, but where any life was wiped out by this process of tidal extinction."

Barnes, Brian Jackson and Professor Richard Greenberg, all with the UA Lunar and Planetary Laboratory, and Sean Raymond of the Center for Astrophysics and Space Astronomy at the University of Colorado, published their study in the article "Tides and the Evolution of Planetary Habitability," in Astrobiology magazine earlier this year.

Jackson, Barnes and Greenberg recently published another paper on the major role tidal forces play in pulling planets into and out of solar system habitable zones. One conclusion in that paper, published in the Monthly Notices of the Royal Astronomical Society, is that the first Earth-like planets found will likely be strongly heated and very volcanically active.

Barnes will talk about it at a departmental colloquium on Tuesday, Dec. 2.

Provided by University of Arizona

Explore further: Far from home: Wayward cluster is both tiny and distant

add to favorites email to friend print save as pdf

Related Stories

Planets can alter each other's climates over eons

Feb 20, 2015

A new study sheds light on how exoplanets in tightly-packed solar systems interact with each other gravitationally by affecting one another's climates and their abilities to support alien life.

Interesting facts about planet Mars

Feb 16, 2015

Mars is a constant point of discussion for space explorers around the world. We've sent dozens of spacecraft there to study it. Some want to land astronauts on it. The planet is just far away to make that ...

Planets orbiting red dwarfs may stay wet enough for life

Feb 09, 2015

Small, cold stars known as red dwarfs are the most common type of star in the Universe, and the sheer number of planets that may exist around them potentially make them valuable places to hunt for signs of ...

Recommended for you

Far from home: Wayward cluster is both tiny and distant

8 hours ago

Like the lost little puppy that wanders too far from home, astronomers have found an unusually small and distant group of stars that seems oddly out of place. The cluster, made of only a handful of stars, ...

An old-looking galaxy in a young universe

Mar 02, 2015

A team of astronomers, led by Darach Watson, from the University of Copenhagen used the Very Large Telescope's X-shooter instrument along with the Atacama Large Millimeter/submillimeter Array (ALMA) to observe ...

Giant methane storms on Uranus

Mar 02, 2015

Most of the times we have looked at Uranus, it has seemed to be a relatively calm place. Well, yes its atmosphere is the coldest place in the solar system. But, when we picture the seventh planet in our ...

Where do stars form in merging galaxies?

Mar 02, 2015

Collisions between galaxies, and even less dramatic gravitational encounters between them, are recognized as triggering star formation. Observations of luminous galaxies, powered by starbursts, are consistent ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.