Discovery of a first planet orbiting a white dwarf

At least one exoplanet has been able to survive the violent transitions that a solar-type star experiences during its lifetime, to the final stage.

In several billion years, when the Sun has swollen to the point of encompassing the orbit of Mars, or even that of Earth, becoming a giant red, will have exhausted all its nuclear fuel, then deflated until it becomes a white dwarf d 'a diameter comparable to that of Earth, will there always be planets around it to testify to it? Astronomers have just made a discovery which proves that this is not impossible! For the first time ever, these scientists have unearthed a giant gas planet orbiting a white dwarf. However, its detection was indirect since what the researchers saw was the evaporation of the outer layers of the planet under the effect of the powerful ultraviolet radiation from the star. In fact, if most of the gases thus torn from the exoplanet escape into space, part of them feed a disc which wraps around the white dwarf and grows at a speed of around 3,000 tonnes per second. The composition of this disc betrays the phenomenon.

The star baptized WDJ0914 + 1914 is located about 1,500 light years from Earth, in the constellation of Cancer. Small, this white dwarf is, however, extremely hot since its temperature is around 28,000 degrees Celsius (about five times the temperature of our Sun). As for the surviving planet, probably quite similar to Neptune, it would be two to four times larger than the star around which it orbits in just ten days and at a distance of about 10 million km. This proximity (on an astronomical scale) is astonishing since the current orbit of the planet is located in the perimeter formerly occupied by the star in the red giant stage. This therefore implies that the giant planet got closer to its star once it became white dwarf, due to gravitational interactions, perhaps with other planets of the system which would also have survived ...

For the moment, obviously, there is nothing to confirm this. However, this unprecedented discovery could lead to other detections of exoplanets orbiting such end-of-life stars. Some, orbiting much cooler white dwarfs, might not be stripped of their atmosphere in this way. And, if others suffered the same fate, the study of the disc forming around the dwarf star could provide valuable information on their atmospheres. These two perspectives are therefore as interesting as the other from a scientific point of view.