New study suggests planets could form more easily than we thought

This artist’s impression shows a young star surrounded by a protoplanetary disk, where dust grains gather together to form planetesimals—the building blocks of new planets. Credit: ESO/L. Calçada.

Have you ever wondered how planets like Earth came into being?

It all starts in the cosmic nurseries of space, where young stars are surrounded by swirling clouds of dust and gas.

Scientists have been trying to piece together this cosmic puzzle for years, and a recent study by a team of astrophysicists from RIKEN and Tohoku University in Japan has brought us one step closer to understanding the process.

When we look at the space around young stars, we see something called protoplanetary disks. These are like the construction sites for future planets.

Tiny dust particles in these disks slowly come together to form bigger chunks, and these chunks can grow into even bigger objects called planetesimals, which are the building blocks of planets.

But how do these dust particles stick together in the first place? This is a question that has puzzled astronomers for a long time.

There are a couple of ways this might happen. One idea is that the dust grains simply crash into each other and stick together, a process known as coagulation.

Another possibility is that the movement of dust through the disk creates dense clumps of dust through a mechanism called streaming instability.

If these clumps get big enough, they can collapse under their own gravity and form planetesimals.

Ryosuke Tominaga and Hidekazu Tanaka, the scientists leading this study, wanted to figure out which of these processes is more important for forming planetesimals.

They built a model to simulate how dust behaves in these protoplanetary disks, taking into account how fast and how sticky the dust grains are.

They discovered that if dust grains collide too fast, they might break apart instead of sticking together, which could be a major obstacle in the growth of planetesimals.

However, their model showed something exciting: both the sticking together and the clumping processes happen at about the same rate and actually help each other out.

This creates a sort of teamwork effect, where the growth of dust grains makes clumps form more easily, and these clumps, in turn, help more dust grains stick together.

This discovery is great news for our understanding of how planets form, suggesting that it might be easier for planetesimals to form than we previously thought. This applies to both icy grains and silicate grains, which are more like the sand on our beaches.

The study, published in The Astrophysical Journal, is still in its early stages, and the model used is quite basic.

Tominaga hopes to use more detailed simulations in the future to get a clearer picture of how planets start their journey from tiny dust grains to the complex worlds we see today.

This research not only sheds light on the mysteries of our universe but also brings us closer to understanding our own place within it.