White dwarf star shows presence of pure oxygen


London: Researchers have discovered a rare white dwarf star with an atmosphere dominated by a pure layer of oxygen – a type of white dwarf that has been theorised to exist but not identified till date.

The finding could challenge the textbook wisdom of single stellar evolution and provide a critical link to some types of supernovae discovered over the past decade.

As relatively small stars (those less than 10 times the mass of our Sun) near the end of their lives, they throw off their outer layers and become white dwarf stars which are very dense.

The high gravity that occurs under such density causes the lighter elements, such as hydrogen or helium, to float to the surface of the star, masking the heavier elements below.

While combing through data from the “Sloan Digital Sky Survey” (SDSS), Kepler de Souza Oliveira Filho, a Brazilian astronomer primarily known for his work on white dwarfs, identified a white dwarf with its outer layer of light elements stripped away, revealing a nearly pure layer of oxygen.

“The identification of this white dwarf provides the first evidence of this phenomenon. One possibility is that interactions with a nearby companion in a binary star caused the white dwarf to bare its oxygen envelope,” suggested Kepler, professor at Universidade Federal do Rio Grande do Sul (UFRGS).

Another possibility is that a massive pulse of burning carbon from the centre of the star, emulating outwards, eliminated the lighter elements, he added in a university statement.

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