Sunday, December 3, 2017

Neutron Starz

Something new I learned this week is that there are objects in our universe called "neutron stars" which astrophysicists barely understand. They are made of a substance which scientists are only now learning more about. Perhaps the most interesting factoid about neutron stars is their extremely high density; the article I read said "the matter inside a neutron star is so dense that a teaspoonful would weigh a billion tons." Of course, I had no idea what they were talking about because they didn't convert to SI units! So I took this task upon myself. A teaspoon occupies the same volume as 4.93 mL, which converts to 4.93E-6 cubic meters. One ton is 907 kg, so 1,000,000 tons would be 9E11 kg. That's heavy stuff. If we divide the mass by volume, we find the approximate density to be 1.84E17 kg/m^3. To put that into perspective, the material in a neutron star is 184 trillion times more dense than water!

The most exciting discussion of the article was about a collision between two of these neutron stars, since this occurrence allowed scientists to learn more about the properties of this stellar material. I was really excited to see that conservation of momentum and rotational kinetics were used in order to determine the limits on the mass and radius. I noticed that the collision must have been inelastic, since they stated "In the collision, the two neutron stars merged into a single behemoth." Although the specifics of how they determined their conclusions are way above the scope of this class, I was able to understand that the collision allowed them to infer that the stars are not "squishy." In other words, the material of the star is not easily compressed. A squishy star would have to be smaller than a stiff one of the same mass, and would thus collapse more quickly in a collision. Since there was a delay, they could infer that the star material was stiff and not squishy. Researchers are still working on finding what exactly these stars are made of, but with more collisions comes more conclusions!

Here's a link to the article: https://www.sciencenews.org/article/collision-illuminates-mysterious-makeup-neutron-stars

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