00:01
We have a neutron star, and it is the remaining core of a giant stellar explosion.
00:06
A neutron star is comprised solely of neutrons, so it makes calculations pretty easy, at least compared to other stars.
00:15
And so what we can do is say it is just one giant atomic nucleus.
00:21
This simplifies our equations even further.
00:26
And so we have a neutron star of mass m.
00:30
And the given is that it is twice as large as the mass of the sun.
00:38
And the mass of the sun, let's just do this right now, is 1 .99 times 10 to the 30th power kilograms.
00:50
And so we're going to hear, for the mass of the neutron star, is 3 .98 times 10 to the 30th power kilograms.
01:01
Okay.
01:03
And we would like to find its radius in kilometers.
01:09
We're also given that we can model it as a nucleus with a radius found by the expression, r equals r0 times a to the one -third power.
01:23
So r -not here is just the average radius of any nucleus, which is going to be equal to 1 .2 times 10 to the 15th meters.
01:38
And a is our mass number.
01:43
In other words, how many neutrons are in our nucleus? because we're not concerned with protons or electrons or anything else because there's only neutrons here.
01:57
And so what a is, it's the total mass of the neutron star, which we know is comprised solely of neutrons, divided by the mass of one neutron...