Introduction to the White Dwarfs

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Introduction to the White Dwarfs

Introduction: 

A small very dense star that is typically the size of a planet. A white dwarf is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula.

The Whirlpool galaxy's central region. Where new bright stars are developing can be seen in the pink regions. Lord Rosse created this image in 1845, using photos from the Hubble Space Telescope and the ground-based National Optical Astronomy Observatories. It's accompanied by a lot more minor irregularity.

• Size:

The white dwarf was discovered to be roughly 2,670 miles (4,300 kilometres) broad, making it far larger than the moon, which has a diameter of 2,158 miles (3,474 kilometres).

• Temperature:

The temperature is almost 179,500 degrees Fahrenheit.

According to New Mexico State University, a white dwarf possesses a similar carbon and oxygen mass to our sun despite being considerably smaller in size—similar to Earth (NMSU). According to NASA, the temperature of a white dwarf can reach 100,000 kelvins.

• Escape velocity:

With a radius of only 8800 kilometres, a solar mass white dwarf's surface escape velocity is around 5500 kilometres per second. With a radius of just 17 kilometres, a solar mass neutron star's surface escape velocity would be an astonishing 125,000 kilometres per second.

• Core:

White dwarfs are usually made mostly of carbon and oxygen. If the progenitor's mass is between 8 and 10.5 solar masses, the core temperature will be high enough to fuse carbon but not neon, resulting in the formation of an oxygen-neon-magnesium white dwarf.

It has a companion galaxy, NGC 5195, in orbit around it. Dwarf in white The leftovers of a star in an advanced stage of stellar evolution, made mostly of degenerate matter with close-packed atomic nuclei and electrons. When a star runs out of nuclear fusion fuel, it becomes a white dwarf. Its outer layer collapse under its own gravity, becoming a planetary nebula, while its core blows off and forms a planetary nebula. When the electrons in the core cannot be compacted any further and instead oppose collapse, the process comes to a halt. The upper mass limit for white dwarfs, according to Subrahmanyan Chandrasekhar, is 1.4 times the mass of the Sun. If a larger stellar core collapses, it must collapse into a neutron star or black hole.

Wild 2, Comet

The white dwarf Sirius B, which has a mass similar to that of the Sun, is about the same size as Earth.

Introduction to the White Dwarfs
Size comparison of Earth and Sirius B.
Source: Wikipedia Commons

In 1910, the first white dwarf was discovered. It was a star 40 Eridani B, which had a surface temperature of 17 000 K but a total brightness so low that it had to be smaller than Earth. Van Maanen's star and Sirius B, a dim companion to the brightest star in the sky, are two other well-known white dwarfs. Sirius B, discovered in 1862, has a mass of nearly the same as the Sun but is contained in a five-times-the-diameter ball. It is ten thousand times fainter than Sirius A, a typical A star.

Though collectively referred to as "white" dwarfs, these degenerate stars actually range in temperature and colour from the hottest, which are white and have surface temperatures as high as 100 000 K, to the coolest, which are red and have surface temperatures as low as 4000 K. Because they lack an internal source of energy, white dwarfs undergo a long cooling phase during which their temperature decreases. Their ultimate fate is to become a black dwarf, a dead star with no light.

White dwarf spectra are befuddling complicated, indicating a wide range of temperature and composition. Their spectra usually have very broad absorption lines; however, others don't have any at all.

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