Featured Research

from universities, journals, and other organizations

Companion planets can increase old worlds' chance at life

Date:
August 1, 2014
Source:
University of Washington
Summary:
Having a companion in old age is good for people -- and, it turns out, might extend the chance for life on certain Earth-sized planets in the cosmos as well. Planets cool as they age. Over time their molten cores solidify and inner heat-generating activity dwindles, becoming less able to keep the world habitable by regulating carbon dioxide to prevent runaway heating or cooling.

For certain ancient planets orbiting smaller, older stars, the gravitational influence of an outer companion planet might generate enough energy through tidal heating to keep the closer-in world habitable even when its own internal fires burn out. But what would such a planet look like on its surface? Here, UW astronomer Rory Barnes provides a speculative illustration of a planet in the habitable zone of a star about the size of the sun. “The star would appear about 10 times larger in the sky than our sun, and the crescent is not a moon but a nearby Saturn-sized planet that maintains the tidal heating,” Barnes notes. “The sky is mostly dark because cool stars don’t emit much blue light, so the atmosphere doesn’t scatter it.”
Credit: Rory Barnes, University of Washington

Having a companion in old age is good for people -- and, it turns out, might extend the chance for life on certain Earth-sized planets in the cosmos as well.

Related Articles


Planets cool as they age. Over time their molten cores solidify and inner heat-generating activity dwindles, becoming less able to keep the world habitable by regulating carbon dioxide to prevent runaway heating or cooling.

But astronomers at the University of Washington and the University of Arizona have found that for certain planets about the size of our own, the gravitational pull of an outer companion planet could generate enough heat -- through a process called tidal heating -- to effectively prevent that internal cooling, and extend the inner world's chance at hosting life.

UW astronomer Rory Barnes is second author of a paper published in the July issue of the Monthly Notices of the Royal Astronomical Society. The lead authors are graduate student Christa Van Laerhoven and planetary scientist Richard Greenberg at the University of Arizona.

Tidal heating results from the gravitational push and pull of the outer companion planet on its closer-in neighbor, Barnes said. The effect happens locally, so to speak, on Jupiter's moons Io and Europa. The researchers showed that this phenomenon can take place on exoplanets -- those outside the solar system -- as well.

Using computer models, the researchers found the effect can occur on older Earth-sized planets in noncircular orbits in the habitable zone of low-mass stars, or those less than one-quarter the mass of the Sun. The habitable zone is that swath of space around a star just right to allow an orbiting rocky planet to sustain liquid water on its surface, thus giving life a chance.

"When the planet is closer to the star, the gravitational field is stronger and the planet is deformed into an American football shape. When farther from the star, the field is weaker and the planet relaxes into a more spherical shape," Barnes said. "This constant flexing causes layers inside the planet to rub against each other, producing frictional heating."

The outer planet is necessary, Barnes added, to keep the potentially habitable planet's orbit noncircular. When a planet's orbit is circular, the gravitational pull from its host star is constant, so its shape never changes, and there is no tidal heating.

And so, the researchers conclude, any discoveries of Earth-sized planets in the habitable zone of old, small stars should be followed by searches for outer companion planets that might improve the inner world's chance at hosting life.

The combined effect of the ancient planet's own tectonics and tidal heating generated by the outer companion, Barnes said, might allow such planets to host some of the longest-lived surface habitats in the universe.

"Perhaps in the distant future, after our sun has died out, our descendants will live on worlds like these."

The research was done through the Virtual Planetary Laboratory, a UW-based interdisciplinary research group. The research was funded through the NASA Earth and Space Science Fellowship Program and the National Science Foundation.


Story Source:

The above story is based on materials provided by University of Washington. The original article was written by Peter Kelley. Note: Materials may be edited for content and length.


Journal Reference:

  1. C. Van Laerhoven, R. Barnes, R. Greenberg. Tides, planetary companions, and habitability: habitability in the habitable zone of low-mass stars. Monthly Notices of the Royal Astronomical Society, 2014; 441 (3): 1888 DOI: 10.1093/mnras/stu685

Cite This Page:

University of Washington. "Companion planets can increase old worlds' chance at life." ScienceDaily. ScienceDaily, 1 August 2014. <www.sciencedaily.com/releases/2014/08/140801091234.htm>.
University of Washington. (2014, August 1). Companion planets can increase old worlds' chance at life. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2014/08/140801091234.htm
University of Washington. "Companion planets can increase old worlds' chance at life." ScienceDaily. www.sciencedaily.com/releases/2014/08/140801091234.htm (accessed December 18, 2014).

Share This


More From ScienceDaily



More Space & Time News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Rover Finds More Clues About Possible Life On Mars

Rover Finds More Clues About Possible Life On Mars

Newsy (Dec. 17, 2014) NASA's Curiosity rover detected methane on Mars and organic compounds on the surface, but it doesn't quite prove there was life ... yet. Video provided by Newsy
Powered by NewsLook.com
Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Reuters - US Online Video (Dec. 16, 2014) NASA's Mars Curiosity rover finds methane in the Martian atmosphere and organic chemicals in the planet's soil, the latest hint that Mars was once suitable for microbial life. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Geminids Meteor Shower Lights Up Skies in China

Geminids Meteor Shower Lights Up Skies in China

AFP (Dec. 16, 2014) The Geminids meteor shower lights up the skies over the Changbai Mountains in northeast China. Duration: 01:03 Video provided by AFP
Powered by NewsLook.com
Raw: Defense Satellite Launches from California

Raw: Defense Satellite Launches from California

AP (Dec. 13, 2014) A U.S. defense satellite launched from California's central coast on Friday after weather delays caused by a major storm that drenched the state. (Dec. 13) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins