Question

Why 1 teaspoon of neutron star material would weigh million tonnes?​

Answer 1

Answer:

Because it's density is very very high.

Answer 2

This is why it weighs so heavy on earth.

The collapsed star is so dense that electrons and protons do not exist separately, but are fused to form neutrons. Despite their small diameters—about 12.5 miles (20 kilometers)— neutron stars boost nearly 1.5 times the mass of our sun, and are thus incredibly dense. Just a sugar cube of neutron star matter would weigh about one hundred million tons on Earth.