A white dwarf is stealing the atmosphere from a Neptune-like exoplanet

Katie Ramirez
December 5, 2019

In what researchers known as "a kind of likelihood discoveries", they discovered an ice large exoplanet - a planet outdoors of our solar system - orbiting an Earth-sized white dwarf.

The scientists want to further study the system to shed light on what could happen to our own Solar System when the Sun reaches the end of its life.

"It was one of those chance discoveries", says researcher Boris Gänsicke, from the University of Warwick within the United Kingdom, who led the study, published today in Nature. He detailed, "For the past 20 years, it's been more and clear that there are remnants of planetary systems around white dwarfs".

To get a better idea of the properties of this unusual star, named WDJ0914+1914, the team analysed it with the X-shooter instrument on ESO's Very Large Telescope in the Chilean Atacama Desert.

Tiny spikes of hydrogen have been unexpectedly detected round this explicit white dwarf. The VLT turned its gaze on the odd white dwarf, and with the help of a powerful spectrograph instrument called X-shooter created a detailed spectrum, or breakdown, of the star's light.

"It took a few weeks of very hard thinking to figure out that the only way to make such a disk is the evaporation of a giant planet", said Matthias Schreiber, an astronomer at the University of Valparaiso in Chile, who was vital to determining the past and future evolution of the freaky system. If such a planet were to orbit the white dwarf, its atmosphere would be slowly evaporated by the intense ultraviolet radiation pouring forth from the white dwarf. Unless, that is, the planet was dropped down after the star turned into a white dwarf. He stated, "It was crystal clear that there was something extremely exciting going on in the system because we detected emissions of hydrogen, oxygen, and sulfur immediately". In fact, the searing star is sending a stream of vaporized material away from the planet at a rate of some 260 million tons per day.

If the material isn't coming from a star, and isn't coming from a rocky planet, the most likely candidate is a gas giant of some sort. This disc is what gives away the presence of the otherwise hidden Neptune-like planet.

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"This discovery is major progress because over the past two decades we had growing evidence that planetary systems survive into the white dwarf stage", said Gänsicke.

Stars like our Sun burn hydrogen in their cores for most of their lives.

The white dwarf was once a star similar to the sun but eventually ran out of fuel and swelled up into a red giant, a few hundred times the size of the sun. Even though the white dwarf is not subjected to a nuclear fusion anymore, similar to the process a normal star goes through, its remaining heat means it is still blazing at 49,500 degrees Fahrenheit (25,000 Celsius).

Scientists have spotted evidence of a Neptune-size planet orbiting a white dwarf. However, until now, scientists had never found evidence of a surviving giant planet around a white dwarf.

Researchers believe its distance from our home planet is roughly 2,000 light years, which is more than 476 times the distance of the nearest star to our Sun. This icy giant travels at a distance of just 10 million km (6 million miles) from the super-hot surface of the white dwarf, and completes a full orbit in just 10 days. If this occurred, the planet would have orbited inside the star, and friction would have slowed it, bringing the planet ever closer to the star's core. But a new example has been found with gas that has been drawn off from a Neptune-like planet.

These findings had been printed Wednesday within the journal Nature.

The team is composed of Boris Gänsicke (Department of Physics & Centre for Exoplanets and Habitability, University of Warwick, UK), Matthias Schreiber (Institute of Physics and Astronomy, Millennium Nucleus for Planet Formation, Valparaiso University, Chile), Odette Toloza (Department of Physics, University of Warwick, UK), Nicola Gentile Fusillo (Department of Physics, University of Warwick, UK), Detlev Koester (Institute for Theoretical Physics and Astrophysics, University of Kiel, Germany), and Christopher Manser (Department of Physics, University of Warwick, UK).

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