Question

See problem 52 in Chapter 13 of the 3rd Edition of Knight for some background information about neutron stars. Consider a neutron star with a mass equal to 0.7 times the mass of the Sun, a radius of 14.2 km, and a rotation period of 1 s. What is the speed of a point on the equator of this neutron star?

What is gg at the surface of this neutron star?

A stationary 1.0 kg mass has a weight of 9.8 N on Earth. What would be its weight on the neutron star?

How many revolutions per second are made by a satellite orbiting 1.0 km above the surface?

Answer 1

Mass of neutron star, M = 0.7*M_sun

M = 1.3923*10³⁰ kg

Radius of neutron star, R = 14.2 km

Time period of rotation, T_o = 1 s

Speed at a point on the equator of neutron star, v = rw = r*2*pi/T_o

Speed at a point on the equator of neutron star, v = 89221.23 m/s

Acceleration at the surface of this neutron star, g = GM/R² = 6.674*10-11* 1.3923*10³⁰ /(14.2*1000)²

Acceleration at the surface of this neutron star, g = 4.61*10¹¹ m/s²

Weight of mass 1.0 kg on neutron star, W = m*g = 1*4.61*10¹¹ m/s²

Weight of mass 1.0 kg on neutron star, W = 4.61*10¹¹ N