In an article published today in the prestigious scientific journal Nature, and in which the astronomer Matthias Schreiber of the Institute of Physics and Astronomy of the University of Valparaíso (IFA) took part, discovered a giant planet, frozen and hidden very similar to Neptune, which orbits around what was the core of a small extinct star, or white dwarf.
This is the first evidence of a gas planet orbiting a white dwarf, in the form of a disk of gas produced from its evaporating atmosphere. “The planet orbits the star (which is a quarter of its size), once every ten days, leaving a gas tail similar to a comet in its path, composed of hydrogen, oxygen and sulfur,” as described by the UV astrophysicist, who is also deputy director of the Nucleo of Planetary Formation (NPF).
White dwarfs are stellar remnants that occur when a star with mass similar to the Sun depletes its nuclear fuel. Then, the outer layers of this star are detached leaving the nucleus inert to the center, which from that moment is called white dwarf.
Currently, about three thousand stars are known to host planets, and it is estimated that most of them will end their lives as white dwarfs. Theoretical models indicate that these planetary systems, including our Solar System, can survive the metamorphosis of the stars that host them.
The discovery, which was made collaboratively by astronomers from the IFA of the UV, the NPF and the Department of Physics of the University of Warwick in England, who used the Very Large Telescope (VLT) of the European Southern Observatory, installed in Chile, suggests that there might be other planets around those stars, waiting to be discovered.
“It is known that the heavy elements we see in white dwarf atmospheres come from the accretion of planetary material such as comets and asteroids. For that reason, they became famous since they allow to study the chemical composition of rocky planets. However, we now find that a white dwarf can also add material from the atmosphere of a gaseous planet and we can see it falling into it, ”said the astronomer.
Matthias Schreiber showed that the hot white dwarf (28 thousand degrees Celsius), produces the slow evaporation of this giant ice cream by bombarding it with high-energy photons and converting its lost mass into a gas disk around the star, which gets more than three thousand tons of material per second.
Future of our solar system
Schreiber warned that “in a sense the finding gives us a vision of the very distant future of our own solar system.” Finally, taking this case to the solar system, the astrophysicist said: “when our star runs out of fuel, in approximately 4.5 billion years, it will eliminate its outer layers, which will destroy Mercury, Venus and, probably, the Earth, leaving the white dwarf to the center of the system. ”
In a complementary article directed by Schreiber and astronomer Boris Gaensicke, published in Astrophysical Journal Letters, astrophysicists detail how this white dwarf will radiate enough high-energy photons to evaporate Jupiter, Saturn, Uranus and Neptune. As in the present finding, part of that atmospheric gas will end up in the white dwarf left by the Sun and will be observable for future generations.
Astronomers argue that this planetary evaporation, and the subsequent accumulation of young white dwarfs, is probably a relatively common process that could open a new window to study the chemical composition of atmospheres.