Colliding planetary discs

When a star forms, it creates a planetary disc.

The disc then makes the planets, asteroids, comets etc.

When a double star forms, not a close binary, but one like Alpha
Centauri, they must both make a planetary disc.

They probably rotate in the same direction, which means that the two
discs must collide head on from time to time.

There are simulations of the formation of the planet system around
*one* star, have anybody made a simulation of a double star formation
?

Regards

Carsten Nielsen
Denmark

but one like AlphaCentauri, they must both make a planetary disc.
They probably rotate in the same direction, which means that the two
discs must collide head on from time to time.

No, they "mustn't", what we tend to see are 2 stars from 1 solar
nebula and 1 shared protoplanetary disc.
jc



--
http://mysite.wanadoo-members.co.uk/jc_atm/

John Carruthers wrote:
but one like AlphaCentauri, they must both make a planetary disc.
They probably rotate in the same direction, which means that the two
discs must collide head on from time to time.


No, they "mustn't", what we tend to see are 2 stars from 1 solar
nebula and 1 shared protoplanetary disc.
jc


Depends... some binary stars are pretty far apart and may evolve
separate planetary discs.

"John Carruthers" wrote in message ...
but one like AlphaCentauri, they must both make a planetary disc.
They probably rotate in the same direction, which means that the two
discs must collide head on from time to time.

No, they "mustn't", what we tend to see are 2 stars from 1 solar
nebula and 1 shared protoplanetary disc.
jc

You mean that you'll get a protoplanetary disc around *both* stars ,
not each their own ?

The material must come from each star, then be driven out by the
magnetic field of the star it is in orbit around. This according to
Fred Hoyle: The Cosmogony of the Solar System.

Of course he only discussed the case of a single star, but if there
are two stars in a binary, and they are far enough from each other,
the protoplanetary discs should form, then be driven out, then I think
they get in the way of each other.

I have seen sources, where they predict that binaries can have
planets in orbit around one component, if they are far enough apart.
This led me to believe that each star has its own planetary system,
made by its own planetary disc.

Regards

Carsten Nielsen
Denmark

The material must come from each star, then be driven out by the
magnetic field of the star it is in orbit around. This according to
Fred Hoyle: The Cosmogony of the Solar System.

Fred was a great man, he'd argue black was blue, the original troll
(except he has since often been proven right). I think the
protostellar nebula rotates around a common barycentre and
condenses/coalesces into a proto planetary disc (also rotating around
the barycentre) in which n- stars form and planetesimals condense.
Quite how these planets migrate though I do not know, nor I think does
anyone else :-)
jc



--
http://mysite.wanadoo-members.co.uk/jc_atm/

Carsten Nielsen wrote:
You mean that you'll get a protoplanetary disc around *both* stars ,
not each their own ?

The material must come from each star, then be driven out by the
magnetic field of the star it is in orbit around. This according to
Fred Hoyle: The Cosmogony of the Solar System.

It *must* do no such thing. It's not as though the star condenses
from an amorphous gas and *then* sprouts a protoplanetary disc. The
disc happens at the same time as the condensation.

I seem to recall that the magnetic field doesn't drive out material
so much as it brakes the rotation of the star. That angular momentum
has to go somewhere, and it goes the only place it can go: the disc.

If the stars are sufficiently far apart, then no collective disc forms
and the two stars separate with their own distinct discs. If, however,
the two developing stars are too close to one another, they stay
tightly together and planets form around the pair.

Of course he only discussed the case of a single star, but if there
are two stars in a binary, and they are far enough from each other,
the protoplanetary discs should form, then be driven out, then I think
they get in the way of each other.

The discs won't intersect, for the reason you point out. Their
particles will interfere with one another, and the extreme parts of
the disc will collapse. You'll likely never get to a point where
planets form out there.

I have seen sources, where they predict that binaries can have
planets in orbit around one component, if they are far enough apart.
This led me to believe that each star has its own planetary system,
made by its own planetary disc.

It can be that way, but there is no reason it *must* be that way.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

When a double star forms, not a close binary, but one like Alpha
Centauri, they must both make a planetary disc.

Once you get far enough apart in a binary, you are also likely looking at
separate formation and subsequent capture of each other --- which would
initially mean separate disks and could mean separate planetary systems.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try http://groups.yahoo.com/group/lunar-observing/

Are you interested in understanding optics?
Try http://groups.yahoo.com/group/ATM_Optics_Software/

To reply, remove Delete and change period com to period net
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They probably rotate in the same direction, which means that the two
discs must collide head on from time to time.

There are simulations of the formation of the planet system around
*one* star, have anybody made a simulation of a double star formation
?

Regards

Carsten Nielsen
Denmark

The material must come from each star,

?????

The material comes from the disk, which coaleses at the same time as the
star.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try http://groups.yahoo.com/group/lunar-observing/

Are you interested in understanding optics?
Try http://groups.yahoo.com/group/ATM_Optics_Software/

To reply, remove Delete and change period com to period net
************************************************** ************

then be driven out by the
magnetic field of the star it is in orbit around. This according to
Fred Hoyle: The Cosmogony of the Solar System.

Of course he only discussed the case of a single star, but if there
are two stars in a binary, and they are far enough from each other,
the protoplanetary discs should form, then be driven out, then I think
they get in the way of each other.

I have seen sources, where they predict that binaries can have
planets in orbit around one component, if they are far enough apart.
This led me to believe that each star has its own planetary system,
made by its own planetary disc.

Regards

Carsten Nielsen
Denmark