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Author Topic: Can Stars form without Planets?  (Read 5274 times)

Offline Airthumbs

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Can Stars form without Planets?
« on: 09/04/2012 22:14:21 »
Does every star we see have at least one planet?  When I look up at the sky It would be a very nice thought to think that every star up there has it's own planetary system....  Apparantly Red Dwarf stars have a 40% chance of having a rocky earthlike planet orbiting in the habitable zone.  TELEGRAPH ARTICLE I cannot find the reference to any scientific paper here so watch out!



 

Offline damocles

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Re: Can Stars form without Planets?
« Reply #1 on: 09/04/2012 22:24:22 »
A fairly large proportion of stars are "double stars" -- two suns orbiting each other. With double stars, there is no necessity for planets to form during the accretion stages of formation, and even if they do there are no stable planetary orbits. So "double star" systems have no planets.

I do not see how a star could form from a cloud of dust and gas into a single body, but I am not an expert, or even well read up in this area. I think that if a star does not have a companion star, then it must have had a planetary system at some stage of its evolution. Conservation of angular momentum pretty much guarantees it.
 

Offline Airthumbs

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Re: Can Stars form without Planets?
« Reply #2 on: 09/04/2012 22:42:22 »
I have to say that Binary stars can have planets, in fact Binaries that have a planet only orbiting one of the stars are known to have an "s" orbit and planets that orbit both Binaries are known to have a "p" orbit. 

"Simulations have shown that the presence of a binary companion can actually improve the rate of planet formation within stable orbital zones by "stirring up" the protoplanetary disk, increasing the accretion rate of the protoplanets within" Elisa V. Quintana, Jack J. Lissauer (2007). "Terrestrial Planet Formation in Binary Star Systems"
 

Offline Geezer

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Re: Can Stars form without Planets?
« Reply #3 on: 10/04/2012 17:08:05 »
I sorta think (meaning I'm making a wild guess) that more than one body is required to form a somewhat stable system. The empirical evidence seems to be mounting too. We keep finding more and more stars that are part of a system. Somebody just claimed to have found a star with eight planets.
 

Offline Ęthelwulf

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Re: Can Stars form without Planets?
« Reply #4 on: 11/04/2012 00:58:08 »
Yes, I would imagine a large asteroid belt could form into relatively large enough objects to be considered as planets. Planetoids are just names for another size of an object. Pluto for instance, is too small to be a planet.
 

Offline Soul Surfer

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Re: Can Stars form without Planets?
« Reply #5 on: 11/04/2012 13:23:21 »
It is interesting to note that binary stars can be formed at all separations.  There are even some called "contact binaries" where the stars actually share a common envelope.
 

Offline Airthumbs

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Re: Can Stars form without Planets?
« Reply #6 on: 25/04/2012 04:34:54 »
Yes, I would imagine a large asteroid belt could form into relatively large enough objects to be considered as planets. Planetoids are just names for another size of an object. Pluto for instance, is too small to be a planet.

With the greatest of respect I don't think you understood my question fully.  Can stars form without planets? 
I take it that the Asteroid belt would be in orbit around a star?  Maybe you thought I meant can planets form without stars?  Which is also an interesting question but then you would have to say can asteroid belts form without stars.  And maybe the answer is yes because they could be in orbit around a Blackhole..........

I'm confused!

That is interesting Soul Surfer.... there seems to be a lot of diversity out there, I love it.
 

Offline CliffordK

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Re: Can Stars form without Planets?
« Reply #7 on: 28/04/2012 21:09:27 »
I'm seeing estimates that the Milky Way has about 300 Billion stars.
But, the estimates are on the order of 200 Billion planets.

I wonder if the number is low.
Logic might indicate that if our lowly solar system has 8½ planets...

Then that number may in fact be quite low.
Perhaps there would be as many as a trillion planets in the Milky Way.

As far as the Asteroid Belt.

Perhaps in the absence of other forces, and given time, an asteroid belt within a certain distance of a star (for example between Mercury and Saturn), will always coalesce into a planet.

What about the asteroid belt between Mars & Jupiter?
Could Tidal Forces from Jupiter be stirring it up, preventing larger planets from forming, or is there just not enough material to make another planet?
 

Offline Pmb

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Re: Can Stars form without Planets?
« Reply #8 on: 28/04/2012 22:06:13 »
I sorta think (meaning I'm making a wild guess) that more than one body is required to form a somewhat stable system.
Geezer - In my opinion that's a very respectable response. In my experience at posting in physics forums over the last 14 years people would far too often post what is really speculations as fact when in actuality it was a mere guess. Bravo to you good Sir! :)
 

Offline CliffordK

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Re: Can Stars form without Planets?
« Reply #9 on: 28/04/2012 22:27:03 »
I sorta think (meaning I'm making a wild guess) that more than one body is required to form a somewhat stable system.
Geezer - In my opinion that's a very respectable response. In my experience at posting in physics forums over the last 14 years people would far too often post what is really speculations as fact when in actuality it was a mere guess. Bravo to you good Sir! :)
If we look at moons, some planets have moons, some don't (Venus). 

It has been hypothesized that moons aid with axial stability of the planet, as well as seismic instability (which may aid in resource distribution).  Uranus must be ignored for the axial stability question.

The question is how that would extend to stars?  The axis of our solar system is quite tilted with respect to the Milky Way.
What is a stable stellar system without planets?
 

Offline Ęthelwulf

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Re: Can Stars form without Planets?
« Reply #10 on: 28/04/2012 22:36:11 »
A fairly large proportion of stars are "double stars" -- two suns orbiting each other. With double stars, there is no necessity for planets to form during the accretion stages of formation, and even if they do there are no stable planetary orbits. So "double star" systems have no planets.

I do not see how a star could form from a cloud of dust and gas into a single body, but I am not an expert, or even well read up in this area. I think that if a star does not have a companion star, then it must have had a planetary system at some stage of its evolution. Conservation of angular momentum pretty much guarantees it.

A good example would be Zeta Reticuli - a binary star system which in cosmological terms, is very close. I forget how close now, maybe 38 light years away? I might be way off with that. Anyway, some exobiologists believe there might be life there, including planets. We haven't detected any planets yet, but we may in the future.
 

Offline Geezer

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Re: Can Stars form without Planets?
« Reply #11 on: 29/04/2012 01:17:16 »
I put in a plug for this gent every so often. FreeCAD is a nice free simulator. If you look down the examples you'll find a simulation of the three body problem using the inverse square law. I have only used FreeCAD for more mundane engineering simulations, but I think it should be possible to expand the three body simulation to n bodies - just don't blame me if it crashes your OS and causes a power outage in your neighborhood.

You'll find it here -

http://www.askoh.com/

It might be one way to test if the "arm wavy" math has any validity.
 

Offline CliffordK

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Re: Can Stars form without Planets?
« Reply #12 on: 29/04/2012 04:35:27 »
just don't blame me if it causes a power outage in your neighborhood.
Oh,
Is it infected with the Bad Times Virus?
 

Offline Geezer

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Re: Can Stars form without Planets?
« Reply #13 on: 29/04/2012 07:22:59 »
just don't blame me if it causes a power outage in your neighborhood.
Oh,
Is it infected with the Bad Times Virus?

Sheeshh! Can't a person get at least some respect around here?
 

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Re: Can Stars form without Planets?
« Reply #13 on: 29/04/2012 07:22:59 »

 

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