Quote:
Originally Posted by C.A.
Hmmm are you suggesting that undetected nomad planets can make up a large portion of mass and gravity to account for dark matter? Do they not have gravity and give off radiation enough to be detected?
If large undetected planets can account for alot of mass, I'm sure smaller objects like asteroids, dust and even gas spread over huge regions of space can account for significant mass.
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I'm not expertly versed in astrophysics, so I don't know the particulars of how exactly you miscount up to five orders of magnitude the number of planets per sun in our galaxy (I assume it has to do with the fact that they are all moving on giant orbits, and rather hard to detect when they are not passing a star since their relatively small to the total volume of a galaxy. That's, as far as I'm aware, how its worked in the past for far off star system detection methods. They watch stars for years and wait for awkward shadows that reoccur with some definitive period which are likely planets in an orbit. You can't do the same with nomad planets as they'd have hundreds upon hundreds of years of time for a single orbit, and with their small size they are not exactly things that stick out against the background). That's a lot of mass (assuming the 100,000:1 upper limit on planet:star ratio) and it *may* account for something but we have no idea how large they are and, still, I don't think they'd account for the very large discrepancies between visible matter and calculated mass of our galaxy. Planets are big but they're pretty paltry in size relative to stars. Let's pretend that each nomad planet is roughly the size of the Earth (mass of 5.97E24 kg) and we'll use our sun (even if its a small on at 1.99E30 kg) as a base reference. The mass of the sun is 300,000 times that of the Earth. So if we had a 100,000 more Earth's floating around, we'd roughly have 1/3 the mass of the sun more mass to our solar system. So let's guestimate this over the whole galaxy to mean that we have roughly another 30% of unaccounted for mass over the current visible... which is a big chunk but its not enough, IIRC, by a long shot.
Moreover, dark matter has observable results to it that doesn't fit standard matter. So there's most certainly something exotic out there that isn't just scattered hydrogen, helium, and Li-7.