Macmillan Learning
When a massive star reaches the end of its life, it is possible for a supernova to occur. This may result in the formation of a very
small, but very dense, neutron star, the density of which is about the same as a neutron. A neutron has a mass of 1.7 x 10-27 kg
and an approximate radius of 1.2 x 10-15 m. The mass of the sun is 2.0 x 1030 kg.

Okay, let's break this down step-by-step:

1) A neutron has a mass of 1.7 x 10-27 kg and an approximate radius of 1.2 x 10-15 m.

So we know the mass and radius of a single neutron.

2) The mass of the sun is 2.0 x 1030 kg.

So we know the total mass of the sun, which is much greater than a neutron.

3) When a massive star reaches the end of its life, it can explode as a supernova.

This supernova can form a neutron star.

4) A neutron star has a density about the same as a neutron.

So we can conclude that a neutron star has a density of:

Density = Mass / Volume

= (1.7 x 10-27 kg) / (4/3 * pi * (1.2 x 10-15 m)3)

= 1.6 x 1017 kg/m3

5) A neutron star forms from the core collapse of a massive star during supernova.

So it has a mass on the order of 1-2 times that of the sun (2 x 1030 kg),

but compressed into a sphere only about 10-20 km in radius.

So its mass would be huge, around 2 x 1030 kg, but confined to a tiny volume,

giving it an immense density, around 1.6 x 1017 kg/m3, the same as a neutron.

Does this help explain the concepts and walk through the calculations? Let me know if you have any other questions!

Nuclear fusion in a star produces elements up to, but no heavier than, ________.
A. iron
B. lead
C. carbon
D. nitrogen