Astronomy Practice Exam

What defines a neutron star or pulsar?

1. A star that has entered its red giant phase

2. The end stage of a low mass star life cycle

3. The end stage of a high mass star life cycle, emitting light and radio waves

4. An early stage in the formation of a galaxy

The correct answer is: The end stage of a high mass star life cycle, emitting light and radio waves

A neutron star or pulsar is indeed defined as the end stage of a high mass star's life cycle. This occurs after the star has undergone a supernova explosion, which occurs when a massive star exhausts its nuclear fuel. The core collapses under gravity, resulting in incredibly dense remnants that are composed primarily of neutrons. These neutron stars are notable for their small radius—often only about 10 kilometers—yet they contain mass greater than that of the Sun. Pulsars are a specific type of neutron star that emit beams of electromagnetic radiation, which can include radio waves. As the neutron star rotates, these beams sweep across space, and if they intersect with the Earth, they can be detected as regular pulses of radiation, giving pulsars their name. Hence, the defining characteristic of a neutron star or pulsar involves both its formation process and the emissions it produces as part of its physical properties.