ALMA reveals hour-scale radio variability from accreting protoplanet PDS70c

Star system: PDS 70 | Distance from the Sun: 370 light years

PDS70c is a young, forming planet still accreting material from its surrounding disk. Using ALMA radio observations at 343 GHz, scientists studied how the planet's radio brightness changes over time. By carefully subtracting the average background signal and analyzing the data in short time intervals, they found that PDS70c's radio emission can vary significantly on hour-long timescales.

In the 2017 data, the planet's radio brightness increased by over 200% during one observation, while other sessions showed no significant change. In 2023, the overall flux was steady, but splitting the data into 20-minute intervals revealed variability at the 2.6-sigma level. This kind of variability is expected if the radio emission comes from hydrogen free-free emission produced by accretion shocks on the planet's circumplanetary disk. The results suggest that the planet's environment is not massive enough to smooth out these rapid changes, supporting the idea that the emission is linked to ongoing accretion.

These findings provide new insights into the physical processes around forming planets and demonstrate the power of time-resolved radio observations for studying planet formation.

Key findings
- PDS70c shows hour-scale variability in radio emission
- Brightness increased by over 200% during one observation
- Variability is consistent with accretion shocks on a circumplanetary disk
- The planet's environment is not massive enough to smooth out rapid changes
- Time-resolved radio data reveal dynamic processes in planet formation

Scientific study

Hourly radio variability of PDS70c from time-differential photometry (external link)