How can astronomers determine the size of tiny Neutron stars but always had trouble with Pluto?

Pulsar J0030+0451 appear 1.3 times the mass of our Sun and has a diameter of 25km. It sits at a distance of 1,100 light years from Earth. Now how it is possible, even with today's equipment to measure a body that is only 25km in size on such a distance, while Pluto, being 2,377km in diameter (determined accurately by New Horizons) could never be accurately measured, even if that dwarf planet is 95 times the size and 1,751,592 times closer by than the Pulsar.

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  • 1 month ago
    Favorite Answer

    If you know the mass (stated as 1.3 times the mass of our sun), then - if it's made solely of neutrons - you can figure the size, knowing how many neutrons can fit in a certain volume, suffering degeneracy. 

    • Snowwie8881 month agoReport

      RIGHT!!!....that makes SENSE..... of course, degenerate matter in the form of neutronium can only be 'packed' to a certain density (after that it become a Black Hole), so yes: Mass equals est. size. And mass can be measured more easily. Thanks. :-)

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  • YKhan
    Lv 7
    1 month ago

    The neutron star produces its own light (actually radio waves), whereas Pluto depends on reflected sunlight. So detecting a neutron star is pretty easy.

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  • 1 month ago

    Pluto being in the neighborhood can be measured directly.  Things far away depend on how we interpret the electromagnetic and gravity waves that travel a long way to reach the earth.  Astronomical "measurements" from outside our solar system are actually estimates based on many theories (how waves travel, how things change over time, effects of high gravity, etc).  We have no way of directly measuring over enormous distances, times, speeds or in extremely high gravity.  Smart people come up with theories and test them against what we can measure, but it is a young changing branch of science and if one of those theories changes then the age, size and distance of virtually everything in the universe can change with it.  Don't be surprised if the diameter or distance of your pulsar goes up 20% or down 20%, it is all an estimate.

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  • Anonymous
    1 month ago

    We can't even see tracks on the Moon where we have allegedly landed a few times.

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  • 1 month ago

    Pluto was a heck of a lot closer and found by the comparison of photographic slides over consecutive nights

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    Source(s): Pluto, refused to comment
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  • 1 month ago

    A dwarf planet is nothing like any star, even tiny nutron.

  • 1 month ago

    If I told you I had an amount of water, and it weighed 8 pounds, you could determine that it was a gallon, and if it were a sphere, you could tell me the diameter.  This is because water is a well-defined substance.  Neutronium, the substance of neutron stars, is well-defined, also.

    Also, to make and maintain a neutron star, there has to be just the right amount of pressure between particles in it, which sets strict upper and lower limits on mass and size.  For an earthly example, think of carbon dioxide.  At room temperature, it's normally a gas, but put it under great  pressure, and it will become a solid.  At just the right pressure, it will become a liquid.

    • don't you have to pile theoretical construct upon theoretical construct to arrive at another theoretical construct when you get there?

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  • 1 month ago

    The size or sizes of neutron stars  can be determined hypothetically by using math and the laws of physics, thermodynamics and quantum mechanics. At this time, we do not have the technology with the capability and resolution to confirm visually by observation, a type of remote field truthing, the sizes of neutron stars. 

    Determining the size of Pluto also had similar problems in resolution

     The Hubble Space telescope in low earth orbit had relative low resolution with all of Pluto being covered by 20 pixels at a distance of 4 billion miles. New horizons came much closer and the sensors had much better resolution so the size of Pluto could be determined much more accurately.

    Although somewhat off topic,  right now the math and various observations tell us that a super Earth planet 9 may be orbiting the Sun, Dr. Brown and his team and another team of scientists still have NOT visually confirmed that Planet 9 really exists. There may be multiple  smaller planet's and KBO's mass and gravity changing the orbits of  of the gas and ice giants. 

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  • 1 month ago

    a lot of it is theoretical bs.

    theoretical physics is a lot like any Liberal Arts discipline. you can make up endless ad hoc hypotheses and claim it's Hard Science. because it is hard for Scientist. this is one of those disciplines where you can get away with not knowing but then adamantly claiming to know.

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