Proxima Centauri is the nearest star to the Sun (4.2 light-years). At least three planets orbit it. A new study based on high-quality optical observations has found that two of them — Proxima d and Proxima b — magnetically interact with their star, each in a different way.
Proxima d is the inner Mars-mass planet. The analysis shows that stellar flares are statistically phase-locked to its orbit (confidence >99.8%). In simpler terms: when Proxima d is at a certain orbital position, the star flares more often. This is a sign of direct magnetic interaction — the planet's magnetic field "hooks" onto the star's field, triggering reconnection events and energy release.
Based on this, scientists produced the first-ever magnetic field estimate for a terrestrial exoplanet: ~16 Gauss for Proxima d (assuming a Mars-sized radius), with a plausible range of 3–280 Gauss depending on stellar field configuration and planetary size. For comparison, Earth's magnetic field is about 0.5 Gauss.
Proxima b — the outer Earth-mass planet — interacts differently. Its signature appears not through phase-locked flare clustering but through modulation of flare intensities depending on its orbital position.
Analysis of chromospheric lines (Halpha, NaI, CaII) revealed clear periodic signals: half the stellar rotation, Proxima b's orbital period, the full stellar rotation, and Proxima d's orbital period. All evidence points to both planets orbiting in the same direction as the star rotates.