Red giant phase confusion....

[mmkilani]

Aldebaran, a star in taurus constellation is currently in its red giant phase. In a red giant phase we understand that expansion of such a star is resulted from lack of continuous energy source to keep its gravitational force from collapsing. Such a star will become so large that the radius and luminous intensity will increase tremendously. Now, if one day our own solar sun energy source is exhausted and a consequent puffing out, our planet earth will move farther away from the present position by about 70% to balance the gravitational radius. How can we reconcile the notion that a galaxy called Aldromenda which is on a collision path with the earth in possibly about 5billion years to come and the prediction of sun red giant phase in possibly about 4.5billionyears time....... I reasoned that, the planet earth would have gone out of the collision course with aldomenda. Open for discussion.

 

[crazyeddie]

Aldebaran, a star in taurus constellation is currently in its red giant phase. In a red giant phase we understand that expansion of such a star is resulted from lack of continuous energy source to keep its gravitational force from collapsing. Such a star will become so large that the radius and luminous intensity will increase tremendously. Now, if one day our own solar sun energy source is exhausted and a consequent puffing out, our planet earth will move farther away from the present position by about 70% to balance the gravitational radius. How can we reconcile the notion that a galaxy called Aldromenda which is on a collision path with the earth in possibly about 5billion years to come and the prediction of sun red giant phase in possibly about 4.5billionyears time....... I reasoned that, the planet earth would have gone out of the collision course with aldomenda. Open for discussion.

There's nothing to reconcile. The death of the sun in 5 billion years has no bearing on the collision of the Andromeda galaxy with the Milky Way, which will happen anywhere from 2 billion to 10 billion years from now, depending on how much lateral or sideways speed Andromeda has. The Earth's sun may still be burning on the main sequence in the early projection, but not in the latter ones. In any case, the Earth will still continue to orbit the sun, no matter what state it's in: main sequence, red giant, or white dwarf......and it will be pulled along if the galactic collision either draws the solar system into a new orbit around the merged galaxies, or if it's ejected into intergalactic space. It's highly unlikely that the sun will collide with another star when the two galaxies merge.

 

[neilsox]

I had not heard the 70% farther away theory before. Perhaps it is not mainstream. If our red giant Sun throws 70% of it's mass beyond Neptune (intense solar wind) then reasonably the radius of Earth's (and the other planets) orbit increases, but likely not by 70%.
If Earth moves to Jupiter's present orbit. That is not even a millionth part of the diameter of Andromeda, so the movement has negligible impact on the collision of the Milky way with Andromeda. Otherwise both you and crazyeddy have the theory correct, as far as I know. You likely should have typed: the hydrogen in the Sun's core was exhausted. Neil