Computer simulations reveal formation mechanisms of wide binary stars

(—Our Sun is a single star. This puts it in a minority of stars because most stars are binaries—two stars that orbit each other and are bound together by their mutual gravity.

Binaries can be very close, sometimes so close that they actually touch each other. Other pairs are extremely wide, with separations up to a light-year or so.

Astronomers have known about such wide pairs for a long time, but how they form has been a mystery. The problem is that the typical cloud cores out of which are born are not large enough to form the widest binaries.

Now Dr. Bo Reipurth of the Institute for Astronomy, University of Hawaii at Manoa, USA, and Dr. Seppo Mikkola of Tuorla Observatory, University of Turku, Finland, have used to come up with a mechanism that accounts for the formation of wide binaries.

Most stars are initially formed in small compact multiple systems with two, three or even more stars at the center of a cloud core. When more than two stars are together in a small space, they gravitationally pull on each other in a chaotic dance, where the lightest body is often kicked out to the outskirts of the core for long periods of time before falling back into the fray.

Meanwhile, the remaining stars feed on the gas at the center of the cloud core and grow heftier. Eventually, the runt of the litter gets such a large kick that it may be completely ejected. But in some cases, the kick is not strong enough for the third body to fully escape, and so it is sent out into a very wide orbit.

The implication is that the widest binaries really should be three stars, not just two stars. Indeed, when astronomers carefully inspect the stars in a very wide system, they often find that one of them is a tight binary. But sometimes it appears that there really are only two stars in a wide system. This means that either wide binaries with only two stars are formed in another way, or something has happened to one of the stars that was once a close binary.

What may have happened is that the stars in the close binary merged into a single larger star. This can happen if there is enough gas in the cloud core to provide resistance to their motion. As the two stars in the close binary move around each other surrounded by gas, they lose energy and spiral toward each other. Sometimes there is so much gas in the core that the two close stars spiral all the way in and collide with each other in a spectacular merging explosion.

The nearest wide binary to us is Alpha Centauri, which is so similar to the Sun that it is almost a twin. Alpha Centauri is actually a close binary, but it also has a small distant companion called Proxima Centauri that is currently about 15,000 times the Earth-Sun distance, or about a quarter of a light-year, away. Several billions of years ago all three stars were born close together, before a violent event sent Proxima out into its wide orbit, where it has been moving ever since.

The paper by Reipurth and Mikkola about the formation of the widest binaries is published in this week's issue of the journal Nature.

Explore further

UKIRT discovers 'impossible' binary stars

More information: Formation of the widest binary stars from dynamical unfolding of triple systems, Nature (2012) doi:10.1038/nature11662
Journal information: Nature

Citation: Computer simulations reveal formation mechanisms of wide binary stars (2012, December 5) retrieved 21 September 2019 from
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Dec 05, 2012
We have the orbital parameters of our Sun's ultra tiny half Jupiter sized brown dwarf star. The period has been verified to about 90% certainty.

Dec 06, 2012
We have the orbital parameters of our Sun's ultra tiny half Jupiter sized brown dwarf star. The period has been verified to about 90% certainty.


Dec 06, 2012
Google: "Vulcan revealed"
Orbital parameters etc. listed.
While it never gets much closer than about 130 AU, but it draws in Kuiper Belt objects. This body and the mass of the Jovians relative to the Sun has only been known about for 4300 years. We are a warrior species so look to the military, not the academics, if you want to find out what is really going on.

Dec 06, 2012
"A well circulated, but unpublished, case occurred on 6 Oct. 1974. The individual was invited on-board a saucer. Figure 3 is the Invitee's description of the alien's interpretation of our alphabet and a description of our solar system. Our planetary symbols were employed by the aliens, but they may have been deduced years before they left on their long journey to our solar system. The first three alien symbols, 12V, translates to G2V. The Sun's recognized astronomical characterization is that of a G2 main sequence spectral class V star."
from vulcan revealed.....
please dont ever mention garbage like that again as science.

Dec 06, 2012
"please dont ever mention garbage like that again as science."
Have you considered a career in astronomy?


Dec 06, 2012
So you really believe that stuff? I'm sorry but thats NOT science. those are a bunch of stories and nonsense about et and a supposed brown dwarf half the size of jupiter. i wont even touch on the size of this supposed brown dwarf, but its not real in any way shape or form. neither are ets visiting earth and interacting with humans.

Dec 07, 2012
The US Air Forces ICBM launch officers and others of the same ilk securing nuclear weapons seem to disagree with you. The half Jupiter sized brown dwarf is ultra tiny even for a brown dwarf. But a brown dwarf is what Dr. J. Allen Hynek (Astronomer) calls it:

Civilian scientific consultant to the U.S. Air Force (1948/49-1969) i.e. 20 years. He began as a debunker of UFO sightings, however he discovered there was what he felt were a significant percentage of these reports which he could not explain. He became convinced they deserved further study by the scientific community.

Dec 10, 2012
We have the orbital parameters of our Sun's ultra tiny half Jupiter sized brown dwarf star. The period has been verified to about 90% certainty.

I see from your profile that someone has graced you with a Ph.D.,, In physics no less. Would you help me with something (in small words and simple phrases if you please)?

Could you briefly describe the "physics" involved of a brown dwarf forming with half the mass of Jupiter? How does this thing work? Does it involve another universe in the multiverse?

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