Binary system Kepler 47 contains at least one planet in its habitable zone. The two stars have different masses, however, and so the habitability of such planets is limited by the shorter lifetime of the larger and more massive star.
Image: NASA/JPL-Caltech/T. Pyle
Planets orbiting binary star systems have to deal with the stresses of more than one star. But new research reveals that close binaries could be as good as singles when it comes to hosting habitable planets. Low-mass twins could make the best hosts, because their combined energy extends the habitable region farther away than would exist around a single star.
After modeling a variety of binary systems, two astronomers determined that stars 80 percent as massive as the Sun, if close enough together, could allow for conditions that would be ideal for hosting habitable planets.
"Potentially, life could exist even more in binary systems than it does in single systems," Joni Clark, an undergraduate at New Mexico State University, told Astrobiology Magazine. Clark worked with astrophysicist Paul Mason of the University of Texas at El Paso.
Pushing the boundaries
Low-mass stars are two to three times more common than the Sun. Their sheer numbers may give them greater odds forhosting planets. But their smaller size also means they have more ultraviolet radiation early in the life of the star and dangerous solar winds in the habitable zone, both important when it comes to maintaining a niche for life to exist. Planets must lie extremely close to small single stars to reap the benefits, a position that brings a number of challenges. Such planets are more prone to be tidally locked, with one face permanently turned toward its sun, and to receive the brunt of any stellar activity. [9 Exoplanets That Could Host Alien Life]
But when two such stars are closely paired, their combined energy extends the habitable region farther away and makes it larger, minimizing some of the threats faced by planets orbiting low-mass stars.
"We have much more room here for planets to hang out," Clark said.
Not just any binary system will work, however. Habitable zones receive the best effect when the low-mass stars are close together, circling each other every ten days or less. Radiation of all types coming from two such closely bound stars would be more consistent, and the planets orbiting them would resemble that of a planet orbiting a single star.
But when the stars are farther apart, the planet's orbit is more likely to be unstable as it feels the tug of gravity stronger from first one star and then the other. When stars are spread out over a distance, orbiting planets would experience significant changes in temperature. With a large enough gap, planets would travel around only one star, with the possibility of occasionally entering the danger zone of the other.
"There are many regions around binary star systems where having a stable orbit simply isn't possible," said Stephen Kane, of the California Institute of Technology. Kane, who studies the habitable zones of planets orbiting binary stars, was not involved in Clark and Mason's research.
Living conditions
Living conditions on the planets would vary based on cloud cover, which could help to both insulate the planet and shelter it from ultraviolet radiation. Such cloud cover could help to protect the planet from the changes it would encounter as it orbits closer first to one star and then to the other.
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12 Comments
Add CommentThough knowing if life exists elsewhere is, of course, worthwhile in itself, I advise caution in thinking that such verification means any more than that.
Reply | Report Abuse | Link to thisOur own planet is teeming with different species, some with a high degree of intelligence, yet we are, essentially, alone. Extending this situation to other planets will not change that.
Further, if life is demonstrated to be universal *and* we are not alone, then where are the signs of this? Maybe I am wrong, but I would expect highly-developed life, especially if it proves we are not alone, to have - over the ages - made itself noticeable. Yet we find no sign of this, even looking to the beginning of the universe.
I think we should prepare ourselves for the shock of discovering, or at least recognising, that we are alone.
i would totally disagree with u, because what if the creatures found in other planets were not as intelligent as us but were the denizens of that planet for millions of years like the dinosaurs once were on earth..
Reply | Report Abuse | Link to this@JABartram - A few things to consider while you wax pessimistic about the possibility of Extra-Terrestrial life (obviously the numbers are estimates, but good enough for this argument):
Reply | Report Abuse | Link to this- ~300 million stars just in our galaxy (a large portion of which we can't even see with current technology)
-We'v been watching the skies for a VERY short period of time (galacticly/evolutionarily speaking), with a VERY small window of the skies covered by that scanning.
- the Milky Way is ~100,000 light years across. If only one ET civilization existed in our galaxy and it was 3/4 of the way across our galaxy, it would take a while for your "signs" of it to get here.
- ~170 billion galaxies in the observable universe... so take those previous arguments and multiply them by a little bit.
YEP... this is all very interesting and profound: LIFE beyond earth? This wasn't even among the questions in the human psyche until very recently since religion dominated thinking of "the heavens" as fixed and static with the earth at "creations" center.
Reply | Report Abuse | Link to this"EXOplanet" is a very recent term... like in the last 15-20 years... going from zero to now thousands... with the certainty, that given the billions of GALAXIES, they are ubiquitious.
BUT here's the rub... the universe... with it's innumerable galaxies/stars/planets/nebulae... is essentially mainly... empty... and lethal to biological life... as well as being absolutely chaotic and "finely tuned" for... black holes!
FURTHER, in this ever changing Cosmos with forces of a magnitude beyond our ken... IF biological-carbon based life emerges... and evolves... and further evolves in a mammalian->primate->homo branch... there are still many threats both locally (volcanism... tectonic shifts... temp/atmospheric changes, etc) and non-local(radiation... asteroid impacts, etc) to eliminate it. The odds for intelligent life to emerge analgous to earth's are remote... and further, for that life to devise the means to communicate beyond it's solar system... in a rapidly expanding Universe... over LIGHT-YEARS are miniscule.
My view is life is poping in and out of existence all over the place... and if a sufficient Solar Mass Ejection... continued Global Warming with all it's implications, a super volcanic eruption or two... an asteroid impact of sufficient mass... or a pandemic of sufficient virulence --->>> you can kiss our "high tech a$$es" goodbye.
THERE is certainly "life" elsewhere... but having all the conditions for "contact" is expecting quite a lot.
Think about what it would take to "explore" the incredible vastness and hostility of space with all its inherent lethal dangers... it's mind boggling.
rumor has it that we are in a binary system and we will soon find out. NASA knows.
Reply | Report Abuse | Link to thisThe Milky Way actually is believed to have over 200 Billion stars. http://www.universetoday.com/22285/facts-about-the-milky-way/
Reply | Report Abuse | Link to thisAlso, JABartram, just what sort of signs would an advanced civilization leave behind and how would you recognize them? We have no idea what they (or us) will use for propulsion, what shape their artifacts might take, or where to look for them.
What's up with basing a story here from "Joni Clark, an undergraduate at New Mexico State University".
Reply | Report Abuse | Link to thisWhat's up with basing a story here on an interview with an undergraduate as reported in "Astrobiology Magazine".
Seriously?
Why would other intelligent life forms on other planets have to be primate based?Life on other worlds may be more alien than we can imagine.Then the chances of finding a civilization the same level or above,becomes astronomical.I not saying that there isn't other life out there,just that contact may be a very remote possibility.
Reply | Report Abuse | Link to thisIf Einstein is correct, and nothing can travel faster than the speed of light ...
Reply | Report Abuse | Link to this... and given the immense distances between stars and galaxies
... what are the chances of detecting any kind of life on another planet, even if it exists?
Charlie, if Einstein is correct, that also means wormholes and warping space could be possible, so, I hope you and he are both right. I just wish I would live to see it.
Reply | Report Abuse | Link to thisMatter is spread across the Universe equally with Hydrogen atoms being the most dominate, statistical probability is life is everywhere?
Reply | Report Abuse | Link to thisMessage from space unclassified by NSA
10/21/2004 approved for release by NSA FOIA case number 41472 written by Dr. H. Champaigne NSA technical journal xiv, no.1
The message decoded was a response from a civilization to Satellite Voyager. The message decoded says they are our closet neighbor just 10.5 light years from Earth. The people live on 3 planets around their Sun with a population of 21 billion. They are a silicon base life form. There is life nearly everywhere and and a warning that some are not so friendly.
In late 2012 the NSA blocked access to the document for general public viewing.
Advanced Alien races use wormholes to travel, using Sun's as Star Gates, traveling into Sun spots and out. Our own Sun has had many Earth size Planets around it and caught on Solar Dynamics Observatory. So previlent and visible NASA shut down image viewing many times for the public. Do you really think we are alone, really?
This work was presented at the American Astronomical Society meeting in January 2013. One thing to keep in mind is that we apply the standard HZ limits for single stars to binaries. While binary periods of less than 10 days provide the most stable HZ limits. Binaries with longer periods, like 20 days, will provide more hospitable planetary environments. This is a subtle, but important detail missed in the article.
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