How is it possible for white dwarfs to have a lower luminosity than the Sun even though the Sun is much cooler than the white dwarfs?

How is it possible for white dwarfs to have a lower luminosity than the Sun even though the Sun is much cooler than the white dwarfs?

White dwarfs have an extremely small surface area to radiate this heat from, so they cool gradually, remaining hot for a long time. As a white dwarf cools, its surface temperature decreases, the radiation which it emits reddens, and its luminosity decreases.

How dense is a white dwarf?

A typical white dwarf is half as massive as the Sun, yet only slightly bigger than Earth. An Earth-sized white dwarf has a density of 1 x 109 kg/m3. That means a white dwarf is 200,000 times as dense. This makes white dwarfs one of the densest collections of matter, surpassed only by neutron stars.

How can white dwarfs be both very hot and have very low luminosity?

The core collapse which creates a white dwarf makes it initially very hot. White dwarfs emit radiation while they cool down over a very long time period. They are very small and have very low luminosity. A star like the Sun on the other hand is constantly producing energy from fusion reactions in the core.

How do you find the average density of a white dwarf?

Summary. The density of the white dwarf stars is reconsidered from the point of view of the theory of the poly tropic gas spheres, and gives for the mean density of a white dwarf (under ideal conditions) the formula ρ = 2·162 × 106 × (M/Θ ) 2.

How is it possible for white dwarf stars to have a lower luminosity than the sun even though they are hotter than the sun?

how is it possible for white dwarf stars to have lower luminosity than the sun even though the sun is cooler than white dwarfs? white dwarf stars have lower luminosity then the sun because it is smaller and less dense.

What is the average density of a typical white dwarf compared to water?

The white dwarf produces pronounced excitation and heating effects in the K-type star’s atmosphere. The white dwarf’s mass is about 0.6 that of the Sun, but its diameter is only 16,000 km (10,000 miles); hence, its density is about 650,000 times that of water.

What is the density of a neutron star?

1017 kg/m3
Neutrons stars are extreme objects that measure between 10 and 20 km across. They have densities of 1017 kg/m3(the Earth has a density of around 5×103 kg/m3 and even white dwarfs have densities over a million times less) meaning that a teaspoon of neutron star material would weigh around a billion tonnes.

What is the density of sun?

1.41 g/cm³Sun / Density

Why do white dwarfs have a lower luminosity?

The stars of this group are known as White Dwarfs, and they have low luminosities because their radii are in general quite small, about the same as the Earth’s radius.

Why are white dwarfs hot but dim?

A white dwarf star can be both hot and dim because of its small size. The star only has a volume around the same size as the planet Earth but compacts…

What is the average density of a white dwarf star?

An Earth-sized white dwarf has a density of 1 x 10 9 kg/m 3 . Earth itself has an average density of only 5.4 x 10 3 kg/m 3. That means a white dwarf is 200,000 times as dense. This makes white dwarfs one of the densest collections of matter, surpassed only by neutron stars.

Why do white dwarfs have no internal pressure?

Because a white dwarf is not able to create internal pressure (e.g. from the release of energy from fusion, because fusion has ceased), gravity compacts the matter inward until even the electrons that compose a white dwarf’s atoms are smashed together.

Why are white dwarfs considered degenerate matter?

Degenerate matter has other unusual properties. For example, the more massive a white dwarf is, the smaller it is. This is because the more mass a white dwarf has, the more its electrons must squeeze together to maintain enough outward pressure to support the extra mass.

What is the density of matter in a neutron star?

Little Green Men The density of neutron stars matter, neutronium, is about 400 million metric tons per cubic inch. Phil tells us this is like squishing _________________ into one single six-sided die. What happens when protons and electrons are pushed together under extreme pressures?