April 1, 2016

Meet Dox, a one-of-a-kind star with an atmosphere of pure oxygen

Researchers recently announced the rare discovery of a distant star with an atmosphere almost completely made of oxygen, according to a new report in the journal Science.

Essential to life as we know it, oxygen is actually quite rare in the universe, and particularly in high concentrations, like the concentration found in the atmosphere of the star in the report known as SDSSJ124043.01+671034.68.


The star, nicknamed Dox, is actually a never-before-seen type of white dwarf star, the study said. Scientists currently know of about 32,000 white dwarf stars.

“Most stars in the universe are in the process of burning hydrogen into helium via nuclear fusion deep inside their cores, which powers their luminosity and provides the thermal pressure that stops them from collapsing under their own weight,” noted Boris Gänsicke, an astronomer at the University of Warwick, in the UK, who wrote an essay on the discovery.

“Stars end their lives once the nuclear fuel runs out, at which point they will either explode in a supernova, or, much more commonly, shed most of their mass and leave behind a white dwarf.”

Dox was found in a mountain of 4.5 million individual star observations, amassed over the last 15 years by the New Mexico-based Sloan Digital Sky Survey. It was discovered by physically looking for strange, new kinds of white dwarfs in a pile of 300,000 survey observations. These observations are basic graphs detailing the colors of light coming from pinpoints of light in the sky.

Gänsicke wrote that spectral data showed Dox’s atmosphere has traces of neon, magnesium, and silicon, but is otherwise all oxygen.

“This white dwarf challenges the textbook wisdom of single stellar evolution and may provide a link to some of the types of supernovae discovered over the past decade,” he commented.

Nearly all other white dwarfs have an atmosphere packed with hydrogen and helium. These lightweight elements are the remnants of the star's elemental fusion fuel that survived from the star's past life. Simply due to their weight, these light elements drift to the top of white dwarfs. This makes the discovery of Dox that much more confounding, the researchers said.


Image credit: Popular Mechanics