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Saloed
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I was wathcing a video about radial velocity method for seeking exoplanet(video) and on 3:05 author writes that momentum of a star equal momentum of a planet. Why?
I assume he's using conservation of momentum of a two-body system. In the rest frame (*) of a star-planet system the total momentum is zero (by definition), hence the planet and star have equal and opposite momenta.Saloed said:I was wathcing a video about radial velocity method for seeking exoplanet(video) and on 3:05 author writes that momentum of a star equal momentum of a planet. Why?
Al_ said:You mention "radial velocity" - so, did the video mean to say "radial momentum"? In a simple system of one star and one planet, would they have equal radial momentum around their shared centre of mass?
sophiecentaur said:If there were more than just one large planet in the system, the wobble of the star would be affected by both of the big planets according to their size. The effect of variation in red shift would presumably have more than one significant frequency component.
Yes - of course - but the wobble (of the star) would produce two variations in red shift, with different periods and the two frequencies would give the clue that there are more than one large planet in the system.stefan r said:The momentum of the system would still add up to 0 when averaged over several orbits.
The momentum of a star and a planet is equal because of the law of conservation of momentum. This law states that in a closed system, the total momentum remains constant. Since a star and a planet are part of the same system, their momentums must be equal.
The mass of a star and a planet do not directly affect their momentum. However, their masses do play a role in determining their velocities, which in turn affect their momentum. According to the equation p = mv, a larger mass would result in a smaller velocity to maintain equal momentum.
Yes, the momentum of a star and a planet is always equal as long as they are part of a closed system. This means that any changes in momentum of one object must be balanced by an equal and opposite change in momentum of the other object.
Yes, the momentum of a star and a planet can change if there is an external force acting on them. For example, if a planet's orbit is affected by the gravitational pull of another object, its momentum will change accordingly.
The distance between a star and a planet does not directly affect their momentum. However, it does play a role in determining the gravitational force between the two objects, which can in turn affect their velocities and therefore their momentum. A larger distance would result in a smaller gravitational force and potentially a smaller velocity to maintain equal momentum.