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Giant planet orbiting a white dwarf star is discovered

publicado a la‎(s)‎ 9 dic. 2019 6:06 por Plataforma Sites Dgac   [ actualizado el 1 sept. 2020 6:33 ]
Scientists from the European Southern Observatory (ESO) said that it is located at the Cancer constellation, 1,500 light years from Earth, and that its size is twice the size of the star.
An artistic rendering of the white dwarf WDJ0914+1914, with the giant nearby planet in a state of evaporation.

(Source: European Southern Observatory)
Using the Very Large Telescope (VLT) at the Atacama desert, in Chile, a team led by researcher Boris Gänsicke, from UK’s University of Warwick, detected a giant planet close to a hot white dwarf, the remnant of a star similar to the Sun. That makes the planet to lose its atmosphere and a gas disc is forming around the star.

Sun-like stars burn hydrogen in their nucleus during almost all of their existence. When they run out of that fuel, they bloat and become giant red stars, hundred of times bigger and they envelope nearby planets.

In the case of the Solar System, that will include Mercury, Venus and even the Earth, that will be consumed by a red giant Sun in about 5,000 million years. Finally, the Sun-like stars lose their external layers and all that remains is a dying nucleus, a white dwarf.

Those star remains can still support planets and it is believed that there are many of those systems in the Milky Way. However, until now the scientists had never found evidence of a surviving giant planet around a white dwarf.

Gas disc

The team studied around 7,000 white dwarves and discovered that one of them was different to the others because when analyzing the star subtle light variations they found chemical elements in quantities that the scientists had never found in a white dwarf before.

“It was one of those accidental discoveries. We knew that there had to be something exceptional about this system and we speculated that it could be linked to some kind of planetary remnant”, said Gänsicke in a study published by Nature.

To get more data on the star, called WDJ0914+1914 and located 1,500 light years away, at the Cancer constellation, the team used an instrument called “X-shooter”, installed on the VLT. The observations confirmed the presence of hydrogen, oxygen and sulphur linked to the white dwarf.

Planetary evaporation

“Studying the very details of the spectra taken by ESO’s X-shooter, the team discovered that these elements were in a gas disc that rotated toward the white dwarf and that didn’t come from the star itself,” according to an article published at ESO’s website.

“Several weeks of work were needed to reach the conclusion that the only way to form a disc of this type is the evaporation of a giant planet,” said Matthias Schreiber, a researcher at the University of Valparaíso’s Physics and Astronomy Institute, who computed the past and future evolution of that system.

According to University of Warwick’s Odette Toloza, it’s the first time that the scientists have been able to measure the gas quantity, as oxygen and sulphur, which hints to the composition of the exoplanets’ atmospheres.

“The discovery also opens a new window to know more about the final destiny of the planetary systems”, added Gänsicke.

Source: European Southern Observatory (www.eso.org)
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