Stellar Discovery: Giant Planet Survived Death of Its Star

The giant planet orbits the white dwarf just outside the gas disc. The blast of high-energy photons that it receives from the white dwarf evaporates its atmosphere, which is mainly composed of hydrogen, oxygen and sulfur. (University of Warwick / Mark Garlick)

(CN) – Astronomers have discovered a new hidden giant planet orbiting a white dwarf star, suggesting for the first time that a planet can survive its sun’s gradual demise, according to a study published Wednesday in Nature.

Researchers found this new planet after noticing unique spikes in hydrogen, oxygen and sulfur within the data of the Sloan Digital Sky Survey, a survey that helps collect information on roughly 10,000 white dwarfs. After further examining the strange body using the Very Large Telescope of the European Southern Observatory in Chile, researchers determined the spikes they were seeing were due to a gaseous disk orbiting the white dwarf known as WD J0914+1914.

Researchers say this discovery shows, for the first time, that a planetary body can survive its sun’s death. The study notes that once a sun has spent all its own fuel it will inevitably shed its outer layers, leaving behind only its now-exposed core. This is what is commonly referred to as white dwarf, and scientists have never discovered a giant planet orbiting one until now.

Boris Gänsicke of the University of Warwick and lead author of the study says this discovery teaches much about the functionality of giant planets.

“This discovery in itself is quite ground-breaking: not only can giant planets survive the demise of their host star into a white dwarf, but they can get yanked onto extremely short orbital periods around the burnt-out core of the was-once-a-star-like-the-sun,” Gänsicke said in an email.

The researchers found that the planet, which is roughly equivalent in structure to Neptune, is about four times the size of its decayed star. The star itself, researchers report, is approximately the same size as Earth.

Researchers say that while there is evidence of its existence, scientists cannot see the giant planet orbiting the dead star directly. This is because the star continues to be so hot that it is evaporating the planet and its atmosphere as the planet orbits around the star every 10 days. This evaporation, combined with the planet’s orbital speed, leaves behind an almost comet-like trail of gases that leaves chemical streaks around the white dwarf.

Scientists are hopefully that despite not being able to observe the planet directly, this revelation will lead to the discovery of other giant planets orbiting white dwarfs around the cosmos.

However, the specific methods used to discover this body might not be usable in the discovery of similar bodies given this planet’s unique characteristics, the researchers said, though data gleaned from it can certainly help the progress of other discovery methods.

Gänsicke hopes these new revelations will lead to more expansive discoveries, and that our understanding of white dwarfs and a giant planet’s ability to orbit them will continue to expand.

“To identify more than this so far unique system, and being able to measure the masses and radii of these planets – that, combined with the knowledge of their atmospheric composition would be an enormous leap in our understanding of giant planets as a whole,” Gänsicke said.

Researchers say that by observing this white dwarf and its orbiting giant planet we are getting a glimpse into the far-away future of our own solar system. Researchers say that in approximately 4.5 billion years our own sun will run out of the needed gases to sustain itself and will begin the transition to a white dwarf – a transition that will destroy Mercury, Venus, and most likely Earth in the process.

Observing white dwarfs such as WD J0914+1914, therefore, gives us a sneak peek into our own cosmic destiny.

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