Orbiting a white dwarf, it was detected thanks to the Keck telescope by a team of astronomers from the University of Tasmania: it offers a vision of what the solar system will be like in a few billion years, when the sun dies.
Artist’s impression of a gas giant orbiting a white dwarf / NASA
A new planet, a gas giant about 6,500 light-years away from Earth, has been detected during its orbit around a white dwarf star in the Milky Way. The discovery published on Nature it is due to a team of astronomers from the University of Tasmania in Hobart, Australia, led by researcher Joshua Blackman, who identified its presence thanks to the Keck telescope, offering a vision of what the solar system will be in a few billion years , after the disappearance of the Earth, when the Sun will have become a white dwarf. “It is proof that the planets around white dwarfs can survive the giant phases of their star”Indicate the scholars.
The planet, similar to Jupiter, was detected using an effect called microlensing, or “gravitational microlensing”, whereby when a star close to the Earth aligns with a more distant star, the gravity of the star in the foreground acts as a lens, amplifying the light of the star in the background. “But if there is a planet orbiting the nearest star, the shape of the lens will be continuously altered by the planet’s gravity as it orbits its star” explain the experts of the National Institute of Astrophysics ( INAF) -. Equally deformed will therefore appear the amplified light coming from the star in the background ”.
These “deformations” of the lens were observed with telescopes at the Keck Observatory in Maunakea, Hawaii, and the nature of the light allowed the researchers to rule out that it was a brown dwarf. “We were also able to rule out the possibility that it was a neutron star, or a black hole. This means that the planet is orbiting a dead star, a white dwarfAdded the French CNRS astronomer and study co-author Jean-Philippe Beaulieu.
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The planet, with the unthinkable name of MOA-2010-Blg-477Lb (this is how the gravitational lensing event was classified) is not the first gas giant ever observed around a white dwarf, but it is the first to be very similar to the gas giant of the Solar System. Its distance from the white dwarf is about 3 astronomical units, comparable to the distance between Jupiter and the Sun, and its mass is also comparable, just 40 percent greater.
Astronomers believe it likely that the white dwarf represents an analogue of the final states of the Sun and Jupiter in our solar system, when in five or six billion years our star will have expanded into a red giant and then died as a white dwarf. Jupiter could therefore survive, while the innermost planets, at least as far as Earth, will already be burned for some time. “Our discovery confirms that planets orbiting at a sufficiently large distance can continue to exist even after their star dies. – concluded Blackman -. Since this system is an analogue of the Solar System, its existence suggests that Jupiter and Saturn could survive the sun’s red giant phase, when the nuclear fuel is exhausted it will self-destruct”.