Dark Star News Archive 2011-12

Planets form around Binary Systems


One of the arguments levelled against the possibility that our Sun might have a distant binary companion is that the planetary system would not have formed under such conditions.  Simply put, the dual 'star' system would be too complex to allow a relatively stable system of planets to form, like that observed in our own solar system.  Part of the reason for that position is the traditional model of how planets form in the first place.  But there's also the question of the dynamics of such a complex system, and how the orbits of planets would be perturbed by such complexity over time.  That issue includes the 'Kosai' effect, which might limit the parameters for a binary sub-brown dwarf companion. 

Well, that whole position is now brought into question by the discovery of a planetary system around a distant binary star system in the Cygnus constellation.  Remarkably, one of the planets discovered there, orbiting two suns, is in their 'habitable zone'.  But amazing as that is, that is not the main repercussion of this discovery.  Instead, the whole theory of planet formation - already rocked by so many bizarre extra-solar planet discoveries - finds itself in urgent need of reformation:

"The presence of a full-fledged circumbinary planetary system orbiting Kepler-47 is an amazing discovery," said Greg Laughlin, professor of Astrophysics and Planetary Science at the University of California in Santa Cruz. "These planets are very difficult to form using the currently accepted paradigm, and I believe that theorists, myself included, will be going back to the drawing board to try to improve our understanding of how planets are assembled in dusty circumbinary disks." (1)

Further, the potential for our own Sun to have had a brown dwarf companion at some point in its history - as hinted at by many experts on the outer solar system - is enhanced by this finding.  Indeed, I wonder whether the perturbing influence of a double stellar system is actually required to create the lumps of accreting matter in the proto-planetary disks from which planets form.  I wonder whether one day we might consider the traditional model of massive planets somehow forming out of a unperturbed, uniform disk to have been a rather quaint concept, but one that was, in hindsight, totally misguided.  Instead, it is the influence of the companion, notable in most star systems, that allows for the creative tension in the planet-forming disk of matter common to both 'stars'.  And by stars, we can mean stellar bodies right down to the sub-brown dwarf companion that might be our own Dark Star.


Written by Andy Lloyd, 5th September 2012


1) "Binary Star Systems may be 'Hot Zones' for Life - New NASA Discovery" 4th September 2012 http://www.dailygalaxy.com/my_weblog/2012/09/are-binary-star-systems-hot-zones-for-life-new-nasa-discovery-suggests-yes.html#more with thanks to Lee