Oxygen-Neon-Magnesium White Dwarf

Definition

An oxygen-neon-magnesium white dwarf is a type of white dwarf star that has a core composed primarily of oxygen, neon, and magnesium. These stars represent the final stage of evolution for low-mass stars, forming after the star has shed its outer layers and the core has collapsed into a dense, degenerate state.

5 Must Know Facts For Your Next Test

1. Oxygen-neon-magnesium white dwarfs are the end-state of stars with initial masses between 8 and 10 solar masses.
2. The high density and pressure in the core of these stars causes the nuclei of oxygen, neon, and magnesium to fuse, creating a degenerate core.
3. Oxygen-neon-magnesium white dwarfs are among the most massive white dwarfs, with typical masses between 1.1 and 1.3 solar masses.
4. These stars have extremely high surface temperatures, often exceeding 100,000 Kelvin, and emit most of their radiation in the ultraviolet and X-ray regions of the spectrum.
5. Oxygen-neon-magnesium white dwarfs are believed to be the progenitors of certain types of supernovae, known as accretion-induced collapse supernovae, which occur when the white dwarf accretes material from a companion star and exceeds the Chandrasekhar limit.

Review Questions

• Explain how the composition of an oxygen-neon-magnesium white dwarf differs from a typical carbon-oxygen white dwarf.
  • The key difference is that oxygen-neon-magnesium white dwarfs have a core composed primarily of oxygen, neon, and magnesium, rather than the carbon and oxygen found in more common white dwarfs. This difference in composition is due to the higher initial mass of the progenitor star, which allows for the fusion of heavier elements in the core before the star sheds its outer layers and collapses into a white dwarf.
• Describe the process by which an oxygen-neon-magnesium white dwarf can undergo a supernova explosion.
  • Oxygen-neon-magnesium white dwarfs can undergo a specific type of supernova known as an accretion-induced collapse supernova. This occurs when the white dwarf accretes material from a companion star, causing its mass to increase and exceed the Chandrasekhar limit. At this point, the core of the white dwarf collapses, triggering a runaway fusion reaction that leads to the star's violent explosion and the ejection of its outer layers into space.
• Analyze the significance of oxygen-neon-magnesium white dwarfs in the context of the death of low-mass stars.
  • Oxygen-neon-magnesium white dwarfs represent a crucial stage in the evolution of low-mass stars. These stars, with initial masses between 8 and 10 solar masses, are able to fuse heavier elements in their cores before shedding their outer layers and collapsing into a degenerate white dwarf state. The formation of these white dwarfs, with their unique composition and high densities, is an important step in the lifecycle of low-mass stars and contributes to our understanding of the diverse outcomes of stellar evolution.

Related terms

White Dwarf:

A white dwarf is a dense, compact star that has exhausted its nuclear fuel and shed its outer layers, leaving behind a dense core composed primarily of carbon and oxygen.

Degenerate Matter:

Degenerate matter is a state of matter found in the cores of white dwarfs and neutron stars, where the electrons are packed so tightly that they become degenerate, exhibiting quantum mechanical properties.

Core-Collapse Supernova: A core-collapse supernova is a type of supernova that occurs when the core of a massive star collapses, resulting in the star's outer layers being ejected violently into space.