Image: Artist's impression by Karen Teramura (UH Institute for Astronomy), background photograph by Wei-Hao Wang
Pairs of stars with separations five hundred times the size of the solar system could be triplets in disguise. New research indicates that many of the known wide binaries (double star systems) may have once contained three stars, and many could still harbor a third.
Bound together by gravity, binary stars make a large percentage of the universe. While most are close, some pairs can orbit with separations thousands of times larger than the distance between the Earth and the sun, known as an astronomical unit. But the wide spread between the two stars means that they couldn't have formed in the same cloud of dust and gas, leaving astronomers to puzzle over how they formed.
"This has been a long-time mystery about these very wide binaries," Bo Reipurth, of the University of Hawaii at Manoa, told SPACE.com.
When a binary becomes a triple
Scientists estimate that as many as 10 percent of stars in the universe are part of wide binaries. Close examination of many of these pairs can sometimes reveal that the central body is not one but two closely orbiting stars, making some wonder just how common such triple systems are.
Working with Seppo Mikkola of Finland's University of Turku, Reipurth proposed that three stars within a cloud of molecular gas and dust are gravitationally bound together soon after formation. The group starts their lives close together, but interactions between the three eventually result in one of the stars being hurled from the group. A strong enough push could remove the star from the system completely, but a weaker one results in a distant orbit. Sometimes the system may last for tens of thousands of centuries before losing the distant star; other times, it may stabilize enough to last billions of years.
The energetic kick that pushes the third star out also drives the two remaining stars together in a close binary. If the ejection comes while the stars are still embedded within the cloud, the remaining pair can even merge together into a single star, making the final system a true binary.
Reipurth described the cloud as "a little bit like walking in mud."
"You feel a resistance," he said.
The drag can cause the pair to spiral together and eventually merge.
According to Reipurth, this would describe many of the systems in which only one star is found at the center.
"This kind of evolution can only happen when you're inside a dense cloud core," he said. "It will not happen after the binary has blown away its gas and dust."
If a planet were orbiting one of these close binaries, it would experience an impressive double sunrise, but a third star would be so distant as to require a telescope to view. Likewise, people on a planet orbiting the distant star would see a single sunset, never realizing that another star or two made up their system. [Infographic: How 'Tatooine' Planets Orbit Twin Stars of Kepler-47]
The research was published online today (Dec. 5) in the journal Nature.
Three's a crowd
Wide binaries, where two stars are gravitationally bound but orbit each other from far away, have long provided a puzzle for astronomers. The vast space between these stars means they could not have formed at such distances within the same cloud core.
Scientists have theorized that wide binary systems could result when one star in a cluster captures another, an event that would require them to drift in the same direction at the same time. This scenario allows the stars to form close together, within the same system, a more likely turn of events.
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Reply | Report Abuse | Link to thisIf astrophysicists could just free their minds from the Laplacian cloud collapse model for the formation of stellar systems, and recognize the naturalness and usefulness of capture models, then they would be able to explain:
1. Wide binaries,
2. Hot Jupiter exoplanet systems,
3. Exoplanet systems with retrograde planets,
4. Exoplanet systems with high eccentricity planets,
etc., etc., ...,
in a simpl,e and less ad hoc, and less credibility-straining manner.
Capture/ejection is how atomic systems are known to form/ionize, and Discrete Scale Relativity unequivocally states that the morphology and dynamics of atoms and molecules in highly excited states are exactly self-similar to exoplanet systems and wide binaries, respectively.
An intellectual revolution is sorely needed in theoretical physics, and has been sorely needed for 40 years!
Robert L. Oldershaw
Discrete Scale Relativity
http://www3.amherst.edu/~rloldershaw
"... the morphology and dynamics of atoms and molecules in highly excited states are exactly self-similar to exoplanet systems and wide binaries, respectively."
Reply | Report Abuse | Link to thisPray tell, what, exactly, is the self-similar atomic scale protoplanetary disk? If molecules are exactly similar to wide binaries (how can they both be self-similar?), what atomic phenomena represents close binaries? Do double nuclei atoms exist? Do electrons have moons? Sorry for being so direct...
Reply | Report Abuse | Link to thisI would recommend that jtdwyer should combat his overt lack of understanding when it comes to Discrete Scale Relativity (aka the Self-Similar Cosmological Paradigm) by spending enough time at:
http://www3.amherst.edu/~rloldershaw
to comprehend this new and highly unfied model for physics at all scales. The answers to his questions, and far more, are readily available for who have more then 10 minutes to devote to understanding the cosmos in a new way.
Regarding the subject of this thread, consider the following.
1. Sumi et al (Nature, 19 May 2011) published solid evidence for trillions of unbound planetary-mass objects roaming throughout our Galaxy.
2. Helmut A. Abt, a highly respected astrophysicist and former editor of the Astrophysical Journal, presented a paper at the most recent AAAS meeting in Alaska that concluded that many exoplanet and multi-star systems MUST be the result of capture processes. It is virtualy inevitable mathematically.
The capture model is poised for a major comeback in astrophysics, and this enhances evidence for self-similarity between atomic and stellar systems.
Ignore barking dogs. There are exciting new ideas available to those who really want to understand the cosmos, rather that Platonic pseudo-science, and are willing to put some time into their studies of these new ideas.
Discrete Scale Relativity would be a good place to start, since it does for physics what Darwinian Evolution did for biology - provide a unifying framework for the whole field.
Robert L. Oldershaw
Discrete Self-Similar (Fractal) Cosmology
If a wide binary can evolve out of a triplet star system formed from the collapse of common gas cloud , it could also evolve from a quadrulet star system formed from common cloud of gas. If a gas cloud can collapse into a triplet star system, what will prevent a dense gas cloud to collapse into star system having multi star system with 4 or more than 4 stars in the common system. These muti star system may ultimately transform to multi close or wide binary star system
Reply | Report Abuse | Link to thisToo bad you didn't have 5 minutes to directly answer any of this "barking dog's" questions - or perhaps you couldn't...
Reply | Report Abuse | Link to thisClose binaries would seem to have likely been formed from a single cloud's accretion event. Wider gravitational couplings might occur in a wide variety conditions. Demonstrating one process that could produce relatively distant gravitational couplings between stars does not necessarily exclude the possibility that perhaps many other methods also produce similar gravitational bindings.
Reply | Report Abuse | Link to thisI'm pretty sure there was an article in SA(within the last couple of years) that showed(suggested) that the siblings of the sun are now spread over many thousands of light years. Just because they are formed in the same "cloud" doesn't mean they are now located next to each other. Which to me also means the opposite...that stars formed in distant clouds might be gravitationally captured if they pass close enough to each other...millions if not billions of years later..
Reply | Report Abuse | Link to thisAstronomers estimate 200-400 billion stars in MW galaxy alone. How could such a large nos. of stars have formed from the collapse of a single gas cloud?
Reply | Report Abuse | Link to thisThere seem to have following possibilities :
i) A large gas cloud might have split itself into smaller chunks of gas clouds. ( But why and how?). Each smaller gas cloud might have collapsed into one or two ( binary) or even triplet star system, as the article suggest. These stars might have remained gravitational linked in close binary system.
ii) A verylarge cloud might have collapsed into a large nos. of stars, may be thousands or even millions. Initially, these stars might have remained gravitational linked. However, in due course, due to internal gravitational dynamic process, these stars might have gone astray from each other and became gravitationally decoupled. I visualize the above process akin to collapse of a water cloud wherein cloud burst out and collapses into a large nos. of water droplets which initially are close to each other but after some time go astray from each other.
Nevertheless the above models of stars formation, it is only speculation. What is the exact process, I think, even astronomers don't know with certainty.