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About doubling the mass of the planets and the sun of our solar system

  1. Oct 7, 2015 #1
    I want to know that if we double the mass of the planets and our sun in the solar system,then will it make any difference in the orbits of the planets?will it be necessary to double the distance of each planet from sun?(I am asking it assuming that the sun on doubling of its mass,don't turn into a black hole,will it?)thank you.
  2. jcsd
  3. Oct 7, 2015 #2


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    What do you think would happen? Why?
  4. Oct 7, 2015 #3
    I think that it is necessary to double the distance as otherwise the gravity will dominate and the orbits might change.is it correct?
  5. Oct 7, 2015 #4


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    Certainly if you keep the distance the same and double both masses you wouldn't end up with a stable orbit. As the the exact answers, you should look up / figure out the equations for orbits and see what you come up with if you just take a single case of the Earth and the Sun with each mass doubling. What happens to the distance to get a stable orbit?
  6. Oct 7, 2015 #5
    Thank you a lot.I will work on it.
  7. Oct 7, 2015 #6


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    Hint: try equating the gravitational force between the star and a planet with the centripetal force needed to keep the planet in orbit.
  8. Oct 7, 2015 #7
    Ok will certainly do.thank you a lot.
  9. Oct 7, 2015 #8


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    You are quite welcome. By the way, welcome to the forum. I think you have probably figured out by now that we are not big on just spoon-feeding answer to questions but rather prefer to help people figure out how to solve problems themselves, and give specific help if/when they get stuck.
  10. Oct 7, 2015 #9
    Yeah now I get it.It is really a great help.I love it.And thank you again.
  11. Oct 7, 2015 #10


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    If we were to instantly double the masses of all of the Sun and all of the planets in our solar system, and keep their current positions and velocities the same, then each planet would end up in a rather elongated elliptical orbit with its current position being close to its furthest distance. This may cause some planets' orbits to cross one another, and they may eventually collide or have close encounters which could place one or the other in a very different orbit.

    Except for collisions or close encounters, most of the change in the orbits of the planets would be due to the doubling of the mass of the Sun.

    In order to make it so that the orbits remain nearly circular, we'd need to either speed up the planets' orbits or increase their distances from the Sun. As phinds mentioned, the way to figure out how to do this is to balance centripetal acceleration with the gravitational force.
  12. Oct 8, 2015 #11
    OK thanks a lot.
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