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Fraser
2006-Jun-06, 06:53 PM
SUMMARY: Instead of forming around a star, planets and moons could collect around objects not much bigger than Jupiter; redefining the concept of a solar system. New research by an international team of astronomers suggests that these "planemos" could form out of gas and dust, and then freely float through space - without a parent star. Astronomers have turned up a few potential examples, including a planet with 8x the mass of Jupiter that has its own disk.


View full article (http://www.universetoday.com/am/publish/planemos_new_planet.html)
What do you think about this story? post your comments below.

altizar
2006-Jun-06, 08:40 PM
It just takes two molecules too close together to start a chain reaction that leads to stellar/planetary formation.

The only difference would be the initial size of the dust cloud acting as the source.

As to the redfining of the term planet. I would still say that it is an object that revolves around a central star that has/is undergoing nuclear fusion. Otherwise I'd label them as Extrenal-Solar Objects.

WaxRubiks
2006-Jun-06, 09:12 PM
But could life evolve on one of these planets in the same way as people postulate about life on Europa ie through heat from the inside of the planet?
I don't see why not.

Ronald Brak
2006-Jun-06, 11:15 PM
Without a nearby star to blow it away a moon around a brown body could retain its original atmosphere which can have a very high greenhouse effect trapping heat generated by radioactive decay and tidal forces, so chemosynthetic life could perhaps exist on the surface. If the rule of many smalls holds there could be more life in between stars than around them.

jhwegener
2006-Jun-07, 06:40 AM
Such objects (planemos and similar) could perhaps even be more common than "regular" stars?
If only a small percentage of galaxys matter exists in such objects they wil08:34 07-06-06l be!
This lead me to ask if the nearest neighbour to visible stars and planet systems normally is such still "invisible"(?) ones? Could even our solar system have such still undetected neighbours?
Could there be some serious consequences for the "average" planetsystem if such small systems are very common?
One such consequence could be a much higher probability two systems migth become very close during a lifetime of several billion years. The "traffic" will be more dense, leading to more "dangerous situations", and even perhaps, collisions.
And all types of "planetary systems" could be less stable than we use to think of. Normally scientists seems they take it for granted that our sun has its companions "for life".
Could it be that many larger and smaller objects, "planets and stars and in-betweens, have different companions during their existence?
(being a planet of different stars or other central objects).

Mike525
2006-Jun-07, 11:09 PM
It just takes two molecules too close together to start a chain reaction that leads to stellar/planetary formation.
There's probably some researchers modeling these possibilities right now.
Just a guess but how about a Gaudin distribution (diff from Gaussian) with mass and population parameters? Once we get enough of a sample maybe we can play with the possible statistical values. My guess is that the population of the mass range of planemos may be higher than stellar systems.

Good points made from a posters here about the potential of heat generation and chemo-bio environments.

Mike525
2006-Jun-28, 09:23 AM
There's probably some researchers modeling these possibilities right now.
I thought I'd take a shot at this....here's a general statistical model idea.

Fact: 250 of the 300 nearest stars to our sun are red dwarfs (RD's)

This is a 5 to 1 ratio of RD's to solar mass stars.

1) How many of these RD's have brown dwarf (BD) companions? Let's say 50% of them do. 125 BD's.

2) How many BD's form independently? Let's take a conservative estimate and say there's a 2 to 1 ratio of BD's to RD's in our neighborhood. That's 500 BD's.

3) How many planemos? Let's use #2 estimate of the # of BD's and consider 500 planemos in our neighborhood.

So add #2 and #3 and we have 1000 potential mini-systems. That's a ratio of 20 to 1 in comparison to solar mass stars in our neighborhood and a ratio to red dwarfs of 4 to 1. Is this a valid distribution?

I mentioned the Gaudin distribution named after its founder, a mathematician who applied it to random matrix theory. It is also called the GUE distribution or "Gausian Unitary Ensemble spacing distribution" which "reflects a "unitary" symmetry displayed by random Hermitian matrices" and applies to chaotic quantum systems.

If we consider the condensing of huge dust clouds into stars and the various effects of gravitation within the cloud volume ie collisions and slingshot effects plus the external gravitational effects there is an ample degree of chaos dynamics taking place.

The Gaudin distribution curve looks like a basic bell curve but skewed to the left and quite steep. The distribution curve would reflect population vs mass and lets consider the mean as 1 solar mass (S) with log2 mass scale. (for example .03125S, .0625S, 0.125S, 0.25S, 0.5S, 1S, 2S, 4S, 8S....).

Since the RD's are mass ranges 0.1S < M <0.4S (approx) then the curve will definitely skew to the left quite sharply and possibly trace out to be a Gaudin curve which can then be "normalized" and analyzed to indicate how many lower than RD mass objects are possible.

If someone has access to mass and population data this would be an interesting way to extrapolate the possibilities.

Anyone have this knowledge and skill set to play with this? I welcome your input.

antoniseb
2006-Jun-28, 11:43 AM
Anyone have this knowledge and skill set to play with this? I welcome your input.

There are factors that you aren't considering, but I think your guess is probably within an order of magnitude (which is all we can hope for without direct observation).

Two factors to through in:
- It appears that higher metallicity stars have larger planets. This may reduce the number of planets orbiting old brown dwarfs.
- We don't really understand the whole star forming process to determine what are the most likely sizes for stars. Again metallicity may play a role. I suspect that most star form in star forming regions, and have their primary growth stopped when a nearby supernova blows away the unbound accreting material. There may starless cores may go through a period of rapid initial condensation that makes the smaller brown dwarf sizes unlikely possibilities for later existance (not impossible, but less likely than bigger ones). There may also be a minimum size starless core that could ever coalesce into a gas giant, without a larger neighbor to help hold the material in place.

Anyway, my point is that I think you're as right in your guess as I could be, but there are things we don't know yet that could be reasons we're both wrong.

Mike525
2006-Jun-29, 06:37 AM
There are factors that you aren't considering, but I think your guess is probably within an order of magnitude (which is all we can hope for without direct observation).

I agree, I would assume several significant factors that I'm not aware of that lend themselves to chaotic dynamics and several that are limiting factors (ie metalicity) that lend to stabilizing the system of formation from cloud to stars/BD's/planemos in various proportions.

In reference to our local neighborhood of 300 stars I wonder if it would be valid to target the interstellar regions, the median regions, and see if our telescopes could detect in the specific infrared range for these lower mass objects.

My assumption is that there is more than ample distance between stars to allow for these relatively vast regions to be occupied by the lower mass objects. At least in the case of our neighborhood.

An analogy would be the branch of sphere-packing mathematics in which various sized spheres would represent the various mass stars and their outer boundary distance which could be considered a "gravitational limit" or even a Lagrangian type effect.

If you were to pack the 300 different sized spheres (local stars) you still get many interstices in which can fit many smaller spheres or lower mass objects. It's pure math modeling but would be a way to determine where to target the telescopes.

I'm sure there's several groups ie Univ. of Toronto astronomy dept. that are on top of this and have models in the making.

homo_cosmosicus
2006-Jun-29, 07:37 AM
Question:
How do I find this story on the front page of Universe Today, or in one of the Categories?
I tried looking it up yesterday but couldn't find it...

What do I think about this story?

It shows that we really need to think hard and decide what acctually is a planet.

R.A.F.
2006-Jun-29, 12:46 PM
It shows that we really need to think hard and decide what acctually is a planet.

I don't know why. "That which we call a rose" and all that.

It's just descriptive words, nothing more. It certainly doesn't change the physical make-up of objects. They are just "handles" which we use to describe something...

No hard thinking required...

Mike525
2006-Jul-23, 06:17 PM
Here's a relevant link with info and interesting comments about "orphan planets" and potential #'s in interstellar regions.

http://www.centauri-dreams.org/?p=689#comments

greenfeather
2006-Jul-26, 02:21 AM
But could life evolve on one of these planets in the same way as people postulate about life on Europa ie through heat from the inside of the planet?
I don't see why not.

If there can be life on planets that don't really have a sun...maybe that's why the standard "alien" picture is of a guy with huge eyes. Because these sunless planets would be pretty dark, wouldn't they? The poor guys would never really have "days". Certainly no need for sunblock...

publiusr
2006-Aug-25, 06:53 PM
Here's a relevant link with info and interesting comments about "orphan planets" and potential #'s in interstellar regions.

http://www.centauri-dreams.org/?p=689#comments

Cool.