Astronomers Discover White Dwarf Star with an Almost Pure Oxygen Atmosphere

Friday, 01 April 2016 - 12:56PM
Astronomy
Friday, 01 April 2016 - 12:56PM
Astronomers Discover White Dwarf Star with an Almost Pure Oxygen Atmosphere
There are plenty of reasons humans could never live on a star, but for one star in particular, we can cross "unbreathable atmosphere" off that list. A newly discovered white dwarf star has an outermost layer of 99.9% oxygen (compared to Earth's 21%), which astronomers had previously only theorized was possible.

Opening quote
"This white dwarf was incredibly unexpected," lead author Souza Oliveira Kepler from the Federal University of Rio Grande do Sul told Popular Mechanics. "And because we had no idea anything like it could even exist, that made it all the more difficult to find."
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A white dwarf star is the final evolutionary stage of stars that don't have enough mass to become neutron stars. When red giants don't have sufficient mass to generate the temperatures necessary to fuse the carbon and oxygen in its core, those elements build up and are left behind once the nebula sheds its outer layers, leaving a stellar remnant known as a white dwarf. 

Usually, the heaviest elements, like carbon and oxygen, sink to the dense center of the star, while the outer layer is dominated by lightweight elements like helium and hydrogen. But this star, called SDSSJ124043.01+671034.68 (nicknamed "Dox") has an almost entirely pure oxygen atmosphere. While trace elements such as neon, magnesium, and silicon make up that tiny .1% of the atmosphere, neither helium or hydrogen can be found anywhere on the star. Astronomers have long postulated that lighter elements could somehow be stripped from the atmosphere over time, but as of now, they have little idea how that could occur.

Opening quote
"What happened to all these light elements?" Kepler said. "How did they all get stripped away?"
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Although scientists theorized this was possible, this is the first direct evidence of a star with this type of atmosphere. Astronomers believe it might even be one-of-a-kind, as there are 32,000 white dwarfs we know of, and none of them have nearly as pristine an oxygen atmosphere as Dox. 

But how did this happen? Scientists are unsure, but Kepler and his co-authors believe that interactions with another star in a binary system may have stripped these elements away.

Opening quote
"I think the main problem is that we [astronomers] have dedicated the last 50 years to calculate the evolution of stars that are not interacting with each other, when at least 30 percent of stars interact with a binary companion," said Kepler.
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They hypothesize that when the other star in Dox's binary system was expanding into a red giant, Dox might have started siphoning some of the hydrogen fuel emitted from the other star onto itself, which would have rapidly raised Dox's temperature and caused a cataclysmic event. 

Opening quote
"When it reached a few million degrees, it exploded," theorized Kepler. "That explosion threw all types of matter out. That's when [Dox] might have lost all its hydrogen and helium. This type of situation is known to have happened with other stars, although it's never been seen to leave just oxygen."
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