
This is the sharpest image ever taken by ALMA — sharper than is routinely achieved in visible light with the NASA/ESA Hubble Space Telescope. It shows the protoplanetary disc surrounding the young star HL Tauri. These new ALMA observations reveal substructures within the disc that have never been seen before and even show the possible positions of planets forming in the dark patches within the system.
In a new Paper, published in Nature, published on 22 Jan 2025, on J. Teiser, J., Penner, J., Joeris, K. et al. The growth of super-large pre-planetary pebbles to an impact erosion limit. Nat Astron (2025) investigate how tiny particles in space, called “pebbles,” grow into larger clusters, which are critical in the formation of planets. Understanding this process helps scientists uncover how planets like Earth formed billions of years ago.
Scientists used a suborbital flight experiment to study how small particles interact and grow under conditions mimicking space. They focused on basalt grains (tiny volcanic rock particles) and observed how they stick together or break apart when colliding. Importantly, these particles were electrically charged, which helped them overcome barriers that normally prevent growth.
Process used.
- Microgravity Environment – This was essential to simulate the weightlessness of space, allowing particles to interact naturally without gravity’s interference.
- Collisional Behaviour – They tested how particles stick or erode depending on their collision speed.
- Numerical Simulations – Computer models were used to support experimental findings, showing how particle charges influence growth.
What they discovered.
- New Insights into Planet Formation – The experiments showed that clusters of particles could grow larger , by several centimetres, thanks to their electrical charges, bypassing a “bouncing barrier” where particles normally fail to stick.
- Conditions for Growth – The team identified a critical collision speed (~0.5 m/s) that determines whether particles stick or cause erosion.
- Foundation for Planetesimals – These findings highlight how small “pebbles” might gather into dense clumps, leading to the formation of planetesimals—the building blocks of planets.
The study revealed that charged particles in protoplanetary disks (the regions around young stars where planets form) can grow larger than previously thought. This mechanism helps explain how early planetary materials overcame significant challenges in sticking together. These results bridge the gap between tiny dust grains and the much larger bodies that eventually form planets.
This research builds our understanding of the early stages of planet formation, showcasing the interplay between physics, chemistry, and the unique conditions found in space.