by kovil » Fri Mar 03, 2006 5:40 pm
Axel,
Not to be too philosophical, but, the edge is a definitionary sort of thing. It is as we define it to be. My guess at the definition is;
A galaxy's boundary is where its gravity tapers off to such an extent that material in the interstellar medium is unsure of what direction to go in.
Under this idea, the long spiral arms in the photo that have gas clouds condensing to form bright star birthing nurserys, and are quite a ways away from the contiguous galactic homogenious area; those island bright star areas are a part of the galaxy, as well as the gas and dust that is not emitting visible light, and probably difusely parsed all over the general area.
I would think a galaxy's bailiwick is as far as its gravity can muster contributions, even tho there is no visible material in some of those areas.
And to include any outlying island clouds within a diameter from the central area, or maybe more.
After all, to whom would those outrigger star clouds be attracted to?
Thusly possession is still 9/10's of the Law of the Universe !
and Gravity be the Judge.
Greatergood,
Galaxies spin because, when the material that drew together which made the galaxy, it was not all going directly toward the compromise center of todays galaxy, so it began in its various fashions, to orbit the agreed upon center of the galaxy.
Any breezes in the primordial hydrogen and dust clouds, would translate into a path that will end up in an orbit around the compromise center of the galactic mass. Any vector will end up turning under gravity and become an orbit, thus the galactic rotation.
Otherwise, under perfect uniform conditions of all material drawing directly toward the center of the new galaxy, it would become a black hole very quickly, as everything would fall straight in.
Any direction other than straight in will end up in a spin of some sort, and by the gravitational interaction between the material in the mean time, it will again compromise into the spiral arms etc that the galaxy shows.
Now an elliptical galaxy is one where the gas cloud was exceptionally still during its clumping into stars. So the stars formed before the galaxy ever started to rotate, as everything was stillness; then the stars began to move as their gravity began to pull slowly on each other unevenly, and we end up with the stars moving around a compromise center of mass, but because there is so much space between the stars they hardly ever collide, they swerve around each other like a in a do-se-do square dance.
Also, the stars condensed and began to shine before the entire cloud had time to condense into a black hole; and then the stars began to dance before they were able to fall into the black hole either.
In this way spacetime, being so large; it kept the matter from falling into a black hole too soon, and thusly the Universe Lives !
Axel,
Not to be too philosophical, but, the edge is a definitionary sort of thing. It is as we define it to be. My guess at the definition is;
A galaxy's boundary is where its gravity tapers off to such an extent that material in the interstellar medium is unsure of what direction to go in.
Under this idea, the long spiral arms in the photo that have gas clouds condensing to form bright star birthing nurserys, and are quite a ways away from the contiguous galactic homogenious area; those island bright star areas are a part of the galaxy, as well as the gas and dust that is not emitting visible light, and probably difusely parsed all over the general area.
I would think a galaxy's bailiwick is as far as its gravity can muster contributions, even tho there is no visible material in some of those areas.
And to include any outlying island clouds within a diameter from the central area, or maybe more.
After all, to whom would those outrigger star clouds be attracted to?
Thusly possession is still 9/10's of the Law of the Universe !
and Gravity be the Judge.
Greatergood,
Galaxies spin because, when the material that drew together which made the galaxy, it was not all going directly toward the compromise center of todays galaxy, so it began in its various fashions, to orbit the agreed upon center of the galaxy.
Any breezes in the primordial hydrogen and dust clouds, would translate into a path that will end up in an orbit around the compromise center of the galactic mass. Any vector will end up turning under gravity and become an orbit, thus the galactic rotation.
Otherwise, under perfect uniform conditions of all material drawing directly toward the center of the new galaxy, it would become a black hole very quickly, as everything would fall straight in.
Any direction other than straight in will end up in a spin of some sort, and by the gravitational interaction between the material in the mean time, it will again compromise into the spiral arms etc that the galaxy shows.
Now an elliptical galaxy is one where the gas cloud was exceptionally still during its clumping into stars. So the stars formed before the galaxy ever started to rotate, as everything was stillness; then the stars began to move as their gravity began to pull slowly on each other unevenly, and we end up with the stars moving around a compromise center of mass, but because there is so much space between the stars they hardly ever collide, they swerve around each other like a in a do-se-do square dance.
Also, the stars condensed and began to shine before the entire cloud had time to condense into a black hole; and then the stars began to dance before they were able to fall into the black hole either.
In this way spacetime, being so large; it kept the matter from falling into a black hole too soon, and thusly the Universe Lives !