This is the tenth lecture series of my complete online introductory undergraduate college course. This video series was used at William Paterson University and CUNY Hunter in online classes as well as to supplement in-person course material. 0:00:01 - White Dwarf Stars 1:07:38 - Novae and Supernovae Type Ia 1:44:23 - Neutron Stars and Pulsars 2:23:33 - Pulsars, X-ray Binaries and Kilonovas The study of stellar remnants, particularly white dwarfs and neutron stars, reveals critical insights into the life cycles of stars and the extreme conditions that arise during their evolution. White dwarfs represent the end state of solar-mass and slightly more massive stars, formed after these stars exhaust their nuclear fuel and undergo a series of transformations culminating in a stellar remnant. This process results in the formation of a white dwarf, characterized by its extraordinary density, typically exceeding 1 million kg/m³. The relationship between mass and radius in white dwarfs is governed by the principles of electron degeneracy pressure, leading to the conclusion that more massive white dwarfs are actually smaller in size. Observations of white dwarfs, such as Sirius B, provide critical data regarding their characteristics and behaviors. As part of binary systems, white dwarfs can interact with their companions, leading to phenomena such as novae and Type Ia supernovae. These explosive events occur when a white dwarf accretes material from a companion star, resulting in thermonuclear reactions on its surface. The cataclysmic explosions of Type Ia supernovae are particularly significant, as they serve as standard candles for measuring cosmic distances due to their consistent luminosity. Neutron stars, on the other hand, represent a different stage in the evolution of massive stars. Formed from the remnants of supernova explosions, neutron stars are characterized by their incredible density, rapid rotation, and strong magnetic fields. Upon the collapse of a massive star’s core, neutrons are formed, leading to a compact object with a radius of only about 10 kilometers but with a mass greater than that of the Sun. Neutron stars exemplify the extreme states of matter, often referred to as nuclear pasta, which may provide insights into the behavior of matter under such intense conditions. One of the defining characteristics of neutron stars is their rapid spin, which results from the conservation of angular momentum during the collapse of the progenitor star. This spin generates a significant magnetic dynamo, creating intense magnetic fields that can exceed one billion teslas. These fields are responsible for powering emissions observed in X-rays and gamma rays, leading to the classification of neutron stars into two categories: pulsars and magnetars. Pulsars emit beams of electromagnetic radiation that sweep across space, producing periodic signals detectable from Earth. The Crab Pulsar serves as a classic example, showcasing the interplay between stellar evolution and high-energy emissions. Overall, the segment emphasizes clear definitions, underlying geometry, and practical observing guidance so viewers can connect the concept to the real sky.