What Distinguishes a White Dwarf from Our Sun?

The primary differences between a white dwarf and our Sun lie in their stages of stellar evolution, physical characteristics, and lifecycle. Understanding these distinctions provides insights into the diverse and fascinating nature of stars.

Stages of Stellar Evolution

Sun: The Sun is presently in the main sequence phase of its life cycle, where it fuses hydrogen into helium in its core. This phase is stable and expected to last for about 10 billion years. Given that the Sun is roughly 4.6 billion years old, it is approximately halfway through this phase.

White Dwarf: A white dwarf is the remnant of a star that has exhausted its nuclear fuel and has shed its outer layers. It represents the final stage of evolution for stars that were not massive enough to become neutron stars or black holes. This transformation occurs after the star has gone through the red giant phase.

Physical Characteristics

Mass

The Sun has a mass of about ({1 times 10^{30}}) kg. Typically, a white dwarf has a mass similar to that of the Sun but is much smaller in volume, often comparable to that of Earth.

Size

The Sun's radius is approximately 696,340 km. A white dwarf, on the other hand, has a radius of about 6,400 km, roughly (frac{1}{100}) that of the Sun.

Density

White dwarfs are extremely dense, with densities exceeding ({10^6}) kg/m3, composed mostly of electron-degenerate matter. While the Sun, being dense for a star, has a much lower average density of about 1.4 kg/m3.

Temperature

The surface temperature of the Sun is around 5500 °C or 5800 K. White dwarfs can have surface temperatures ranging from about 5000 K to over 100,000 K, varying depending on their age and cooling history.

Lifecycle

Sun

Eventually, the Sun will evolve into a red giant in about 5 billion years, then shed its outer layers, leaving behind a white dwarf.

White Dwarf

After its formation, a white dwarf will gradually cool and fade over billions of years, eventually becoming a cold, dark remnant.

Implications

While the Sun is a middle-aged star actively fusing hydrogen, a white dwarf is a dense, cooling remnant of a star that has completed its nuclear burning phase. If the Sun were magically replaced by a white dwarf of the same mass, Earth would turn into an ice ball due to the insufficient heat and light.

Stars with mass below the Chandrasekhar limit (