Magnetic field of GJ 436 b revealed by planet-induced changes in its star's activity

Star system: Gliese 436 | Distance from the Sun: 31.9 light years

GJ 436 is a red dwarf star with a Neptune-sized planet, GJ 436 b, orbiting close by. Scientists have long suspected that magnetic interactions between such planets and their stars could produce detectable signals, but direct evidence has been rare. In this study, researchers analyzed 17 years of spectroscopic data and found repeated increases in the star's activity that match the planet's orbital period and the star's rotation.

The team developed a new model to explain these signals as the result of star-planet magnetic interactions. By studying the timing and strength of the activity enhancements, they estimated the magnetic field of GJ 436 b to be between 6 and 110 gauss. This is the first time such a measurement has been made for a warm Neptune, and it provides clues about how planetary magnetic fields can affect the ability of planets to keep their atmospheres.

These findings open new ways to study the magnetic fields of exoplanets and their effects on both the planets and their host stars, helping us understand the conditions that allow planets to retain their atmospheres over time.

Key findings
- GJ 436 b causes periodic increases in its star's activity
- Signals match the planet's orbit and the star's rotation
- Magnetic field of GJ 436 b estimated at 6–110 gauss
- First such measurement for a warm Neptune
- Results help explain how planets keep their atmospheres

Scientific study

Planet-induced Periodic Modulation of Stellar Activity in GJ~436: Insights into a Warm Neptune's Magnetic Field (external link)