Physics experts answer this for me.... How do we know this true?

Question

Neutron stars can pack more than a sun's worth of material into a city-sized sphere. A few cups of neutron-star stuff would outweigh Mount Everest.

We have only been to mars, a rover on a saturn moon, have sent probes out to charter the universe, Voyager is by the farthest but still no where near a neutron star. How do they know that a few cups of neurton star "STUFF" (which is a great scientific term) would out weigh Mt Everest.

I am well aware by the way that astronomers used the European Space Agency's XMM-Newton X-ray Observatory and the Japanese/NASA Suzaku X-ray to survey three neutron-star binaries: Serpens X-1, GX 349+2 and 4U 1820-30. They also studied the spectral lines from hot iron atoms that whirl around in a disk just beyond the neutron stars' surfaces at speeds reaching 40 percent light speed.


BUT what are the odds that they are completetly wrong about all of the measurements in deep space?

Answer 1

Estimation and theory.

The nearest neutron star is several generations away and would be a very poor place to visit so we may not get anywhere near one for quite some time. However, we can observe them in our telescopes (including radio telescopes). We know certain things about the universe and we use those constants to tell us what else is going on elsewhere.

For example we know that the sun is mostly hydrogen and when an element is burned then it gives off a spectral light pattern that is unique to the element. Therefore when we see hot gases and stars we can take spectral readings to determine what is in them.

As for neutron stars we only have theory to go on. We know the gravity force, we know the size of a sun that is needed to create that gravity force and we infer other things from there. We know the size of a neutron, the strength of the strong and weak nuclear forces inside of an atom and then we determine how much a sample size of neutron star matter would weigh. We then check the size of the neutron star from the dust cloud it attracts and we calculate the weight of the star from there.

Since quantum theory explains the universe, chemistry and so much else we know it is correct and then we can use it to determine what is going on in regions of space that we can only observe.

Classical physics is pretty easy to understand once you are able to wrap your head around it and the power of gravity is constant. Astronomers can use it to calculate the orbit of other items, the speed of falling gas and how massive objects interact. That’s why we can plot a course to Jupiter and then Saturn and beyond with only a few minor course corrections on the way.

The reason why Steven Hawking chose astrophysics was because he could do thought experiments to determine how much mass a black hole needs or the size of a neutron star; and all of it can be done in his head. He had a choice of the very large or the quantum world of the very small, and since there were no cyclotrons (atom smashers) nearby he went for astrophysics.

All the calculations for what we know in the universe are similar; based on constants like the speed of light, the force of gravity and the quantum properties of an atom. Because we can’t go there we have to do the study and research all in theory, but it is a theory around which our universe is constructed so the astrophysicists feel pretty safe.

It all holds together for the same reason that H20 holds together, if our understanding is wrong then a lot of theories are going to be upset. The problem is that when a fundamental change is made in the field that is exactly what happens. For example prior to Steven Hawking White Dwarf matter was thought to be the densest matter in the universe. This is the stellar stuff left over after a sun of our size dies.

Now you see why dark matter and dark energy are so important. Does a black hole weigh as much as we think it does or does dark energy enter the equation somehow. Could dark matter lie inside of neutron stars to increase their mass? We don’t think so, but we can’t be sure. What if the speed of light is a limit due to the proximity of gravity and not effective in deep space? We don’t know and until we get Star Trek type technology the only way we can know is through our theories and understanding of the fundamentals.

Answer 2

Well, the easy answer is that that point source has an intense gravitational field which warps space around it. We can see the effect on the light coming from more distant stars. Light is subject to gravity bending. Some neutron stars are also close to other bodies and we can see the gravitational effects on them and the radio pulses as material is crushed onto the star.
In 1967, Jocelyn Bell and Antony Hewish discovered regular radio pulses from the location of the Hewish and Okoye radio source. This pulsar, was later interpreted as originating from an isolated, rotating neutron star. The energy source of the pulsar is the rotational energy of the neutron star. The largest number of known neutron stars are of this type (See Rotation-powered pulsar).

In 1971, Riccardo Giacconi, Herbert Gursky, Ed Kellogg, R. Levinson, E. Schreier, and H. Tananbaum discovered 4.8 second pulsations in an X-ray source in the constellation Centaurus, Cen X-3. They interpreted this as resulting from a rotating hot neutron star. The energy source is gravitational and results from a rain of gas falling onto the surface of the neutron star from a companion star or the interstellar medium
http://en.wikipedia.org/wiki/Neutron_star

There has been conciderable research on this and it is unlikely that another explanation will supplant it since this one fits the real observed evedence so well.

For a fun read about the effects pick up a copy of Neutron Star by Niven. It's a collection of short stories. In The first of the short stories is Neutron Star. Basically, a pilot has to fly a superstrong space ship around a Neutron star. The trouble is the previous crew was killed in the attempt. However, the pilot, Shaffer, must do the mission for the super intelligent beings, the Puppetters, else risk going to prison because Shaffer is broke and debtors go to prison in the future (could have used this for present day Enron).

The rest of the short stories are fun, not too deep, and the pages just fly by. The Soft Weapon is a story with the introduction of the Kzin, a race of war-like cats. This story was later adapted to the old cartoon show "Star Trek", of the early 70s.

Answer 3

At the moment there isn't any proof that such a star exists outside of theory. Such a star was proposed to exist only one year after the neutron was actually proposed itself (even the neutron is a theory by the way; there isn't any way to prove that it exists yet either). Its existence is credited to the supernova of a giant red star and is believed to be the result of a supernova in the crab nebula c. 1050 A.D. But, still, it is merely a theoretical model. At the moment it is just as plausible to believe that the supernova of a giant red star could result in a pound of cottonballs strung together by blue rubber bands.

Answer 4

Huge.