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Can our Nuclear weapons destroy a Neutron Star?

  1. Mar 10, 2009 #1
    Does anyone know if an average Neutron star with a diameter of 10 miles, was headed towards Earth.. would our Nuclear weapons be able to physically destroy it? Assuming our technology can provide a direct hit, and do it in time. If so, then how many Megatons would the Nuke need to be, and how many nukes would be required?
     
  2. jcsd
  3. Mar 10, 2009 #2
    10 mile diameter would mean a radius of 8,047m, and a volume of 2,182,454,900,272 m3. Using an average density of 5 * 1017 kg/m3 gives a mass of about 0.5 solar masses. The largest nuclear bomb ever detonated (Tsar Bomba) was 50 megatons, or about 2 * 1017j. If all that energy was transferred to kinetic energy it would result in a change in speed of 0.00000065 m/s. Keep in mind that is the largest nuclear bomb ever built, and we assumed every single joule would transfer to kinetic energy. In reality the effect would be much smaller.

    There is an even bigger problem though. Even if we had enough energy to significantly move the star out of our path it would still mess with orbits. Half a solar mass, could easily move Earth out of our orbit.
     
  4. Mar 10, 2009 #3

    Nabeshin

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    The bomb would never make it to the neutron star. Tidal forces would destroy it far before it did.
     
  5. Mar 10, 2009 #4

    mgb_phys

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    If you want to blow it APART - the gravitational binding energy of a star is =3/5 GM^2 /r

    So a 10km/0.5Msol neutron star = 3/5 * 6.6*10^-11 * (10^30kg)^2/5000m
    Is about 10^46 joules,a megaton of TNT is about 5x10^15 Joules.
    So you would a mere 10^30 perfectly placed warheads.
     
  6. Mar 10, 2009 #5
    Suppose that we're somehow able to slightly deflect the neutron star so that it will collide with the Sun. Then the Sun and the neutron star will merge. The mass could be larger than the critical mass and the whole thing will collapse into a black hole!
     
  7. Mar 11, 2009 #6

    Chronos

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    Neutron star collision is a likely mode for stellar mass black hole formation in binary star systems. Solo stars tend to blow apart before reaching the critical mass. It is an unlikely scenario in our solar system [fortunately] because our sun does not have a companion [at least not one massive enough to be of concern]. A rogue neutron star could do the trick, but our galaxy is a very large shooting galaxy. The probability is remote. With regard to the initial inquiry, our nuclear devices would be useless. The entire mass of planet earth could not provide sufficient energy to measurably divert an object of such mass.
     
  8. Mar 11, 2009 #7
    I'm reminded of reading a while back that if a marshmallow was to free fall to the surface of a neutron star from about 1 AU, it would hit with the force of a megaton hydrogen bomb due to the NS having an escape velocity of about 80% the speed of light. A megaton is 5e+15 joules which is equivalent to about 45 grams which is about the weight of an egg (which is at least in the region of a marshmallow!) so it looks like what ever hits the surface from free-fall is expected to be completely annihilated, all (or at least very nearly all) of the mass of the object converting to energy.
     
    Last edited: Mar 11, 2009
  9. Mar 11, 2009 #8
    I think a better option would be to move the Earth AWAY from the path of an incoming Neutron Star!
     
  10. Mar 14, 2009 #9
    Whehe :) !

    Could anyone calculate how much the orbit of the earth will be changed if everyone in China jumps at exactly the same time?
     
  11. Mar 14, 2009 #10

    russ_watters

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    That's easy: zero!
     
  12. Mar 14, 2009 #11
    Shouldn't the earth's direction theoretically change just a tiny little bit for a tiny little time (for as long as the Chinese people are in mid-air)?
    At least, that is what I would expect due to conservation of momentum.

    It wouldn't help much if you'd want to avoid hitting a neutron star anyway :p .
     
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