Slashdot Mirror
Unruly Milky Way
empaler writes "Space.com is running a story about the movement history of the local group near our solar system. The belief until now has been that after an initial period of chaos in our galaxy, it had since 'been rather calm'. 'But this turns out not to be true. Stars have been perturbed all the time throughout the Milky Way history.'"
In the cases of both stars or galaxies apporaching each other to the point of *collision*, there is almost always some orbital component, in which case angular momentum is conserved as the get closer.
If the universe were nice and tidy, even the impressive accelerations seen there would be quite predictable. But complicating matters are the realities of *open systems* such as binary - or other multiple star - systems that *shed* mass from one star to a companion, or instabilities that may result in a star assuming a new size or perhaps *blowing up*.
One wonders where the initial assumption came from: the belief until now has been that after an initial period of chaos in our galaxy, it had since 'been rather calm'.
It seems it's just a slightly modified version of the geocentric view of the universe, in the sense that *that* view was hard to shake because it threatened not only the religious views but the general sensibilities of many people. If it *looked* like things moved around the Earth - so the story goes - Interestingly, it was the observations of those willing to travel a bit, whether Eratosthenes measuring the Earth or countless mariners - along with some good logic - that built a *database* that would allow others to get a handle on cosmic movement to a greater extent.
When we have looked out through the big domes over the last 90 years or so and seen these *violent* things - supernovae, etc - occurring in distant places - because we are capable of seeing so many *times* at once - It must have seemed like our part of the universe was pretty quiet.
But in this case it was taking the time to not rush to judgement (or to disprove an assumption that had been rushed) in that these astronomers "spent 15 years making 1001 nights of observations to detail the motions of more than 14,000 stars that are currently in the solar neighborhood"
That's a lot of time and a lot of stars for a research paper that will added to the file as 'done that'.
Stars do collide - I'm sure quite frequently given the number of them. It's just a question of how likely it is to happen to any one particular star - ie: ours.
Sorry, but stars collide quite rarely, because they are so astonishingly small compared to the space around them. Even in galactic clusters -- as dense as space gets when one is looking at stars -- stars rarely physically collide.
Now, star SYSTEMS collide. That means that in a galactic cluster, two solar systems can pass closely enough to cause orbital disruption. This would be especially a risk to life, as any disruption of a star's Oort cloud would cause an incoming rain of cometary objects.
But that being said, the frequency of stars physically colliding is unimaginably small.
Even when galaxies collide, it's a gravitational "collision" and not a collision like a car hitting a wall. When galaxies collide, there are no stellar collisions. Yes, people get a hole-in-one in a golf course. But to go to the original example, if the tee was ten miles from the cup, how often would that happen? Keep in mind that stars are not aimed. :)
About the only way for stars to collide would be gravitational capture with something causing the orbit to lose energy. With that, one star would spiral into another (or more reasonably the two stars would spiral toward each other).
Supermassive black holes do not require stars collding into them. The huge quantities of dust and gas in the center of a galaxy are sufficient. And easier to capture.