Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Hannah LS on 06/12/2018 09:14:00
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Ralph asks:
Do coronal mass ejections change the trajectory of the Sun within the galaxy like thrusts would a spacecraft?
Any thoughts?
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CMEs can have velocities from 20-3200 km/sec, with an average of 489 km/sec. The escape velocity from the surface of the Sun is 618 km/sec, so the higher speed CMEs will escape the Solar system.
As to how much this will effect the Sun's motion:
The average mass of a CME is 1.6e12 kg. If we assume a top end velocity for the CME, the velocity change generated owuld be in the order of 2.6 picometers per second* At this rate, it would take the Sun ~12378 years to move 1 meter from its original position. During which time, other CMEs will have occurred, all pointing in different directions, On average, they will cancel each other out. So the net movement of the Sun due to CMEs over any time period will be exceedingly small, and over long scales averages out to being none.
* This number is a tad high, as it just used the CME ejection velocity directly, and doesn't account for the effective velocity loss caused by climbing out of the Sun's gravity well.
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CMEs can have velocities from 20-3200 km/sec, with an average of 489 km/sec. The escape velocity from the surface of the Sun is 618 km/sec, so the higher speed CMEs will escape the Solar system.
As to how much this will effect the Sun's motion:
The average mass of a CME is 1.6e12 kg. If we assume a top end velocity for the CME, the velocity change generated owuld be in the order of 2.6 picometers per second* At this rate, it would take the Sun ~12378 years to move 1 meter from its original position. During which time, other CMEs will have occurred, all pointing in different directions, On average, they will cancel each other out. So the net movement of the Sun due to CMEs over any time period will be exceedingly small, and over long scales averages out to being none.
* This number is a tad high, as it just used the CME ejection velocity directly, and doesn't account for the effective velocity loss caused by climbing out of the Sun's gravity well.
Very informative. Given that the trajectory of the sun is determined in part by the gravitational influence of (primarily) the rest of the galaxy does the loss of mass caused by nuclear fusion have any effect on that trajectory?
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does the loss of mass caused by nuclear fusion have any effect on that trajectory?
The energy of nuclear fusion is radiated equally in all directions, providing no net thrust to the Sun.
The mass of the Sun will be slightly less due to nuclear fusion and CME, and slightly more due to swallowing the occasional comet orbiting the Sun.
But the center of mass of the Sun will continue on its original trajectory.
Does the position of the Sun change?
Oumuamua, the recent visitor from outside our Solar System took an hyperbolic path through the Solar System.
It has been said that in fact Oumuamua was virtually at rest compared to the average velocity of nearby stars, the "local frame of reference".
The relative velocity between the Sun and Oumuamua was due to the velocity of the Sun.
The slight bend in the path of Oumuamua would have imparted a miniscule change in velocity to the Sun.
- How much of a change depends on the mass of Oumuamua
- This mass is rather uncertain, since astronomers didn't notice it until it was moving away
- Mass and size estimates were assuming "typical" asteroid composition and albedo (reflectivity).
Listen: https://after-on.com/episodes-31-60/040