Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: watsisname on November 23, 2010, 11:06:22 pm
-
The Sun steals comets from other stars (http://science.nasa.gov/science-news/science-at-nasa/2010/23nov_aliencomets/)
My mind was blown by this, yet in hindsight it makes so much sense. The Oort cloud, assuming it exists, is freaking huge, and being so far out there those comets are extremely loosely bound to us. Which means that even a modest encounter with another sun with a similar Oort cloud would cause comets to be exchanged between the two stars. Such encounters should happen pretty regularly throughout our solar system's history.
This might also shed some light on the "Nemesis" (http://en.wikipedia.org/wiki/Nemesis_%28star%29) hypothesis for mass extinctions, which argues that a large object (brown dwarf perhaps) orbiting our sun sometimes sweeps through the Oort cloud, thus knocking comets toward the inner solar system. With this new model, perhaps it's close encounters with other solar systems that cause the extinction events, instead of some mysterious binary which we have no direct evidence for.
-
This is part of the foundation of Gef ideology!
-
you have to realize that most of the stuff in the oort cloud is orbiting at very low speeds. it doesnt take much to send something into the sun or to fling it completely out of the solar system. so when these objects collide, they just kinda bump into eachother and its enough to change their orbits drastically without completely destroying the objects.
-
It's indeed true that with lower orbital velocity, a smaller Δv is needed to change the orbit, but there's two other considerations to be made:
1: With lower orbital velocity, the resulting change in momentum from a collision is also less.
2: The volume taken up by the Oort Cloud is enormous, much more so than the asteroid belt. As a result, the average density is extremely low, thus making collisions extremely rare events.
Unless you have things orbiting in vastly different directions (possible in the case of the Oort Cloud, I wouldn't know) then collisions alone are not enough to cause a tremendous change in the orbit. I'd imagine that most interactions are gravitational rather than collisional in nature.
-
It's indeed true that with lower orbital velocity, a smaller Δv is needed to change the orbit, but there's two other considerations to be made:
1: With lower orbital velocity, the resulting change in momentum from a collision is also less.
2: The volume taken up by the Oort Cloud is enormous, much more so than the asteroid belt. As a result, the average density is extremely low, thus making collisions extremely rare events.
Unless you have things orbiting in vastly different directions (possible in the case of the Oort Cloud, I wouldn't know) then collisions alone are not enough to cause a tremendous change in the orbit. I'd imagine that most interactions are gravitational rather than collisional in nature.
question is could a collision or gravitational interaction extend an orbit such that it could come under the influence of objects in another stars cloud. i mean this stuff is already a light year out and under the influence of very little gravity.
-
Yes, most certainly for both cases. Again the effect of a collision depends almost entirely on how different the orbits of the colliding objects are. If they are in nearly the same orbit and going in nearly the same direction, then the collision velocity is almost zero, while if one thing is going in the opposite direction of the other then the collision velocity is twice the orbital velocity. Most renditions of the Oort cloud show a big disk that spreads out into a spherical shape (which requires objects with random/chaotic orbits), so if that interpretation is correct then then that adds to the case of collisions having more significant effects.
That said, I still think collisions would be extremely rare events given the size of that region of space. It's probably interaction with other stars passing a few LY away from us that causes the majority of disruption, and by extension the transfer of material from one cloud to the other as the article demonstrates.
-
so she stole from some measly comets, she's hot enough that I can forgive her.
-
maybe she never owned the comets to begin with, maybe the comets are revolting against countless eons of bondage (not the good kind).
-
No! Bad Sol!
How dare you :p
-
I would have thought, though, that unless the Sun was of a significatly higher mass than its sister stars, it would have been more like a game of Pass the Comet rather than actual theft, i.e. more a case of swapping than stealing?
-
its just a matter of writers anthropomorphizing the universe to make their articles suck less.
-
I would have thought, though, that unless the Sun was of a significatly higher mass than its sister stars, it would have been more like a game of Pass the Comet rather than actual theft, i.e. more a case of swapping than stealing?
IIRC most of the closest stars are brown dwarfs.
-
its just a matter of writers anthropomorphizing the universe to make their articles suck less.
This. :p
On a related note, this (http://en.wikipedia.org/wiki/Gliese_710) wikipedia article was also a good read.
tl;dr: Gliese 710 will pass about one light year from Sol (that's 1/4th the distance to the current closest star) in another 1.4 million years, very likely disrupting our Oort Cloud a bit when it does.
-
I would have thought, though, that unless the Sun was of a significatly higher mass than its sister stars, it would have been more like a game of Pass the Comet rather than actual theft, i.e. more a case of swapping than stealing?
IIRC most of the closest stars are brown dwarfs.
As I understand it, dwarf stars are common all over the place, and when you are dealing with an object moving at something like 500,000 miles per hour in relation to the core of the Milky way, over a period of several billion years, those stars may no longer be anywhere near us. it depends on a lot of stuff we don't know with regards to relative angles of velocity etc.
I'll admit that it doesn't rule out the possibility that the Sun was the only main series star to evolve in our stellar nursery, but a look at most nurseries, or something like the Pliaedes cluster suggests that this would be an extremely rare occurance, though again, I'll stress, not impossible.
-
A thief you say?
(http://www.descent2.com/goodies/3dmodels/thinman/previews/3d_065.jpg)
so she stole from some measly comets, she's hot enough that I can forgive her.
Can you forgive the Bandit for stealing all your weapons and then loosing them all when u find him again? I think not.
-
The theifbot is significantly less hot and significantly more annoying than our beloved sun.
Then again, when that thing gets in my eyes while I'm driving... :mad:
I'll admit that it doesn't rule out the possibility that the Sun was the only main series star to evolve in our stellar nursery, but a look at most nurseries, or something like the Pliaedes cluster suggests that this would be an extremely rare occurance, though again, I'll stress, not impossible.
Well, not strictly impossible I suppose... but so ridiculously unlikely that I'd never bet on it. Molecular clouds have to contain a given amount of mass in order to collapse (see "Jeans' Instability Theorem" (http://en.wikipedia.org/wiki/Jeans_instability)). Once they start collapsing, they don't stop until the cloud gets disrupted by the hot winds from the newly formed stars. Inevitably a bunch of stars are formed by the time that happens.
IIRC red dwarf stars take up the largest percentage of the stellar population in our neighborhood. Can't say much about brown dwarfs though, they're notoriously hard to detect. :/