When we talk about stellar flares, we usually imagine a brief increase in a star’s brightness that quickly fades away. But for FU Orionis (FU Ori), a star located 1,200 light-years from Earth, the flare turned into an 85-year radiation burst that is a trillion times more powerful than the largest solar radiation. The flash is still going on, and researchers have finally solved the mystery of this incredible event: the intense evaporation of the planet.
According to scientists, the planet, about 10 times larger than Jupiter, came too close to its young star. The young star vaporizes the planet into pieces, and the material lost in this literal inferno is ejected onto the star, causing this continuous and violent outburst.
Protostars, the initial stages of stellar life, feed on the protoplanetary disks around them. However, the details of how something as extreme as FU Ori could be produced from these disks were not clear.
“These disks feed the growing stars with large amounts of material, but they also feed the planets. Previous observations have given tantalizing hints of a young massive planet orbiting this star very closely. Several ideas have been put forward as to how a planet might have triggered such an outburst, but the details have never been clarified. “We have discovered a new process that can be called the ‘disk hell’ of young planets,” says Professor Sergei Nayakshina of the University of Leicester.
Simulations built by the researchers showed that the planet forms far away from the star and migrates inward. Once the distance between the planet and the star is less than one-tenth the distance from Earth to the Sun, things go badly. The disk material at that distance around such a young star is so hot that it sets the entire planet on fire, burning through its atmosphere. The planet itself becomes food for the star.
“This was the first star to experience such an outburst. We now have a couple dozen examples of such flares from other young stars forming in our corner of the Galaxy. Although FU Ori events are extreme compared to normal young stars, based on the duration and observability of such events, observers have concluded that most forming solar systems flare about a dozen times while around the protoplanetary disk,” added study co-author Dr. Vardan Elbakian of Leicester.
The team believes that if the model is correct, it could change the way we think about young star systems. They are no longer places of quiet growth, with planets slowly increasing in size. They will be violent and chaotic, and many young planets will burn for their stars.