That always confused me. We have an Oort cloud, whose members we cannot resolve very well/at all. Why do we assume only our star has such a thing? If all stars did, that isn't enough mass to explain dark matter?
The total mass of the Oort cloud is guessed at (3×10^25 kg), or about five Earth masses. With dark matter, we are talking about roughly 5.6x the amount of the total solar system mass. The Oort could would need to be about 371,691x more massive than it is.
Could be an anthropic explanation for that. In a solar system with a hypothetically-"normal" Oort cloud, comets and debris from the cloud might wipe out life on the habitable inner planets every few hundred million years, never allowing it to advance to human-like levels.
So we might be here only because our solar system is surrounded by an unusual amount of nothing.
But we also look at a lot of other stars in the sky. If every single one (or almost every single one) had a massive 5x mass Oort cloud around it, it would affect the light we see from that star.
Consider that we can currently detect differences in luminosity small enough to tell whether an Earth-size planet is passing between us and the star. A 5x mass Oort cloud would be thousands of times more mass than that. It would have noticeable effect on luminosity.
And, while our sun has an Oort cloud, there are a lot of stars out there that probably don't--too small, too big, too hot, too young, too old, etc.
Well for that explanation to scale up, the Oort Cloud would have to total about 5x the mass of the sun. That would have a pretty good chance of perturbing the orbits of all the planets, and vice versa.
A bit of Googling tells me that the current estimate of its mass is in the order of 5-10 Earth masses--not nearly enough to explain dark matter.
Google "sun percentage mass solar system" and the highlighted answer is "By far most of the solar system's mass is in the Sun itself: somewhere between 99.8 and 99.9 percent."
Please don't just disagree when you don't know what you are talking about.
I think you've misinterpreted my post. The "No" was in response to this:
> That always confused me. We have an Oort cloud, whose members we cannot resolve very well/at all. Why do we assume only our star has such a thing? If all stars did, that isn't enough mass to explain dark matter?
No, that isn't enough mass to explain dark matter, since it's only 0.1% to 0.2% of the mass of the solar system.
The text I quoted was in complete agreement with what you and others have posted. I was pointing out that the questioner's point had already been answered.
Ok, that's just a really confusing way of communicating, nobody is going to puzzle that out when the obvious way of looking at your response is disagreement with the grandparent.
