Young Stars can Evaporate Nearby Disks Before They can Form Planets

Many planetary systems may get snuffed out before they even get a chance to form, according to new research. The culprit: nearby stars, capable of evaporating entire protoplanetary disks just when they begin to form.

Stars tend to form in clusters as a single giant nebula fragments into many smaller pieces. Naturally, some stars will form first. Among those stars will be large, hot ones, capable of pumping out tons of intense high-energy radiation.

And where does all that radiation go? Right into the disks of gas and dust that swirl around neighboring, less-developed stars.

Francisca Concha-Ramírez, a graduate student at the University of Leiden, led research involving large numbers of computer simulations of newly-forming planetary systems. The simulations took into account the complicating effects of radiation from nearby stars.

They found that when neighboring stars are too close, the radiation from those stars blows away dust from young protoplanetary systems. This deprives those systems of the crucial building blocks for constructing planets, potentially robbing those stars of planetary systems.

Concha-Ramírez then compared her simulations to observations of nearby star-forming regions, like the Orion Nebula. “Our simulations matched the observations. We saw that discs with many neighboring stars were lighter than discs with few neighboring stars. The radiation from stars evaporates the dust in the discs in a process that we call photoevaporation. Photoevaporation is the biggest cause of the discs’ weight loss.”

The results suggest that for a protoplanetary disk to survive, it has to get away from its neighbors. One way to do that it through a collision, which may have happened in the early days of our own solar system.

“A collision may have taken place between our circumstellar disc and another disc,” says Concha-Ramírez. “We can see proof of this at the edge of our solar system, in the region of the planet Neptune. Here there are suddenly much fewer asteroids, which suggests that another disc could have nabbed material. And there is another interesting clue that there might have been a collision between discs: asteroids that, in relation to the Earth, orbit the sun on a different plane. These asteroids probably come from another disc.”