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SkepticJ
2013-Dec-15, 07:23 AM
Binary masses have long been known to be stable arrangements, orbiting around a common barycenter.

A thought occurred to me, would fractal binary systems be stable?

e.g. A (composed of worlds 1 and 2) and B (composed of worlds 3 and 4) orbit about the common barycenter between them?

If this would be stable, how deep could the fractal system go? Could world 1 actually be composed of 1a and 1b, and so on?

Not that these would be likely to form naturally, just that the physics of it works . . .

Shaula
2013-Dec-15, 07:29 AM
If the perturbations to the larger system due to each layer are small enough then yes they are stable.

http://en.wikipedia.org/wiki/Castor_%28star%29 is an example - A double star with another double star in orbit around it. In orbit around this quadruple system is another double star.

ngc3314
2013-Dec-15, 01:11 PM
To ease searching, the most common descriptor for this arrangement in astronomy is hierarchical.

SkepticJ
2013-Dec-16, 03:01 AM
What about the L4 and L5 points between the two (or composite) bodies at each scale, would they remain "islands of stability", assuming the mass at each is low enough?

SkepticJ
2013-Dec-16, 03:03 AM
That's really cool about Castor. If there are any planets there, that'd be a wild sky.

chornedsnorkack
2013-Dec-17, 12:24 PM
No one seems to know what Castor A and B consist of.

Hornblower
2013-Dec-17, 02:13 PM
No one seems to know what Castor A and B consist of.

Oh yes they do. Each one is a very close pair of spectral type A main sequence stars. One of them has an orbital period of about 9 days and the other one 3 days, so they are closer together than the Sun and Mercury. The two pairs are separated by several billion miles and orbit their common center of mass in a period of some 400 years.

chornedsnorkack
2013-Dec-17, 02:55 PM
Oh yes they do. Each one is a very close pair of spectral type A main sequence stars.
Thatīs one of the versions. The other is that each pair consists of one type A main sequence star, and one red dwarf.

Both versions are found in recent and apparently confident sources. Can anyone find a source that addresses both versions and clearly proves one of them by observations, debunking the other?
(Note that since Castor A and B are two binaries, it is not inconceivable if one of them includes two type A stars, and the other 1).

Hornblower
2013-Dec-17, 06:45 PM
It looks like I spoke too soon. In hindsight I don't know why I did not think of the possibility of M companions. The total magnitude seemed rather low for four A stars.

chornedsnorkack
2013-Dec-17, 10:01 PM
This:
http://books.google.ee/books?id=DR9j2PODQOwC&pg=PA93&lpg=PA93&dq=Castor+spectroscopic+binary+components

suggests that their nature as single lined spectroscopic binaries should make it clear that the satellites are dim.