White Dwarf

Context

• Only a smidge bigger than the moon, a newfound white dwarf is the smallest of its kind known.

About

• A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel.
• Near the end of its nuclear burning stage, this type of star expels most of its outer material, creating a planetary nebula.
• Only the hot core of the star remains.
• This core becomes a very hot white dwarf, with a temperature exceeding 100,000 Kelvin.
• The white dwarf then cools down over the next billion years or so.
• Many nearby, young white dwarfs have been detected as sources of soft, or lower-energy, X-rays.
• Recently, soft X-ray and extreme ultraviolet observations have become a powerful tool in the study the composition and structure of the thin atmosphere of these stars.
• 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.
• Earth itself has an average density of only 5.4 x 103 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.

Composition

• Usually, white dwarfs are composed of carbon and oxygen (CO white dwarf).
• Neon Magnesium Helium white dwarf may also form.

https://www.sciencenews.org/article/white-dwarf-star-smallest-ever-found-moon-size-most-massive