What Are White Dwarf Stars?

Summary of Scientific Concepts and Discoveries about White Dwarf Stars

Definition: White dwarfs are the burned-out cores of stars, primarily composed of carbon and oxygen, with outer layers of helium and hydrogen.

Formation:

• Stars with an initial mass up to 3 or 4 solar masses expand into red giants after exhausting their hydrogen fuel.
• Upon ceasing fusion, these stars expel their outer layers, forming a planetary nebula, leaving behind the core that becomes a white dwarf.

Characteristics:

• White dwarfs are extremely hot, with temperatures exceeding 100,000 Kelvin.
• They are very dense, containing about the mass of the Sun but with a radius similar to that of Earth.
• A teaspoon of white dwarf matter can weigh up to 100 tonnes.
• The surface gravity is approximately 350,000 times that of Earth.

Cooling Process:

• Without ongoing fusion, white dwarfs cool over billions of years and eventually become invisible, transitioning into black dwarfs.
• No black dwarfs are currently expected to exist as the cooling process exceeds the current age of the universe (13.8 billion years).

Interactions in Binary Systems:

• In binary systems, white dwarfs can accrete material from a companion star, potentially leading to:
• Collapse into a neutron star.
• Increase in temperature, triggering a runaway reaction that results in a supernova explosion.

Featured Researchers/Sources

• NASA
• Hubble Space Telescope