chornedsnorkack

2011-Oct-20, 09:01 AM

How fast is the Sun undergoing brownian motion due to weak collisions with stars?

The relaxation time of Milky Way is quoted as in the order of 10^14 years. The orbital period of Sun is 10^8 years, so about 10^6 times smaller. Since the velocity grows with square root of time, the uncertainty of Sunīs velocity after 1 orbital period is 10^-3 times of... what? The translational orbital speed (250 km/s) or the peculiar velocity (mere 20 km/s)?

Also, how does the position uncertainty of Sun scale with time? To the power of square root of time like speed, to the power of square root of the cube of time, or to some other power?

The relaxation time of Milky Way is quoted as in the order of 10^14 years. The orbital period of Sun is 10^8 years, so about 10^6 times smaller. Since the velocity grows with square root of time, the uncertainty of Sunīs velocity after 1 orbital period is 10^-3 times of... what? The translational orbital speed (250 km/s) or the peculiar velocity (mere 20 km/s)?

Also, how does the position uncertainty of Sun scale with time? To the power of square root of time like speed, to the power of square root of the cube of time, or to some other power?