What Is the Estimated Number of Homeless Planets in Our Galaxy?

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Discussion Overview

The discussion revolves around the estimated number of "homeless" planets in our galaxy, specifically the claim that there may be around 100,000 times as many wandering planets as there are stars. Participants are exploring the implications of this estimate, its validity, and the potential mass contribution of these planets to the galaxy.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant expresses skepticism about the claim of 100,000 homeless planets for every star, suggesting it seems excessively high.
  • Another participant questions the lack of photographic evidence or more substantial stories supporting the existence of such a large number of homeless planets.
  • A participant references a different estimate, suggesting there are about twice as many freely floating planets as bound planets, with the number of bound planets roughly equal to the number of stars.
  • Concerns are raised regarding the small sample size of microlensing studies that inform these estimates, with only 11 detections leading to a broader inference.
  • A later reply clarifies that the original researchers are not claiming to have proven the numbers but rather providing an upper bound based on current data and extrapolating from the mass-function of brown dwarfs.
  • One participant points out that the extrapolation to smaller planets remains uncertain, expressing skepticism about the ratio of smaller planets to Jupiter-sized planets.

Areas of Agreement / Disagreement

Participants generally express skepticism about the high estimate of homeless planets, with multiple competing views on the validity of the claims and the methodologies used to arrive at these numbers. The discussion remains unresolved, with no consensus on the accuracy of the estimates presented.

Contextual Notes

The discussion highlights limitations such as the reliance on extrapolated data, the small sample size of current observational studies, and the dependence on definitions of "homeless" planets versus bound planets.

JonDE
Number of "homeless" planets

So I stumbled upon this article and wanted to get others opinions of it. The short and long of it is it is claiming that there are roughly 100,000 X as many planets wandering about our galaxy (not attached to a star) as there are stars in our galaxy. Seems a little high to me.
Further can anyone make an estimation on how much mass this would be (percentage wise) of our galaxy? The article has some information that would be helpful.
http://www.voanews.com/english/news...Be-Awash-with-Homeless-Planets-140350363.html

p.s. I was exagerating when I said a little.
 
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I think if this were true there would be better/more stories and at least one picture of this discovery.
"Strigari also says there is a slight chance that two nomad planets could collide, flinging bacterial debris into other solar systems."

I've learned (correct me if I'm wrong) that when galaxies collide that there's not even a slight(not a unit of measurement either) chance of 2 stars colliding. Also, I think it is playing a lot of the "life out there" hype.
 


That number seems really high, and the one I'm familiar with is ~2x freely floating planets as bound planets (and the number of bound planets is ~ the number of stars).

See: http://arxiv.org/abs/1105.3544v1

These microlensing studies have a very small population of detections (only 11!), from which they infer a population of hundreds of millions of planets, so I'm somewhat skeptical of the results (but their statistical analysis appears to be sound).
 


Nabeshin said:
That number seems really high, and the one I'm familiar with is ~2x freely floating planets as bound planets (and the number of bound planets is ~ the number of stars).

See: http://arxiv.org/abs/1105.3544v1

These microlensing studies have a very small population of detections (only 11!), from which they infer a population of hundreds of millions of planets, so I'm somewhat skeptical of the results (but their statistical analysis appears to be sound).

Just a minor correction. The arxiv link you gave says there are twice as many Jupiter size planets as stars (actually the same thing my article said).
From your link
"Here, we report the discovery of a population of unbound or distant Jupiter-mass objects, which are almost twice (1.8_{-0.8}^{+1.7}) as common as main-sequence stars"

So it leaves open how many smaller planets could be out there. I am skeptical that there are 50,000 X as many smaller planets as Jupiter sized planets, unless someone has a link to that.
Also it does seem to be a very small sample size as you said.
 


First, a correction. Strigari et al aren't claiming to have proven the numbers, merely giving an upper bound based on current observational data and the mass of the Galaxy that's not bound up in stars. The 100,000/1 ratio is based on extrapolating the mass-function of brown dwarfs down to Pluto-mass objects. And, surprisingly, the observational limits are consistent with the high figure. In true scientific spirit, the researchers suggest ways of making the numbers harder based on piggy-back observations - using data from other large-scale observational studies.
 

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