Radio aurora in LSPM J0036+1821 shows Jupiter-like magnetic activity

Observations of the L3.5 dwarf LSPM J0036+1821 (also 2MASS 0036+1821) reveal persistent radio auroras similar to those found on Jupiter. By combining radio and optical data over four years, researchers confirmed a rotation period of approximately 3.08 hours and identified complex magnetic processes driven by electron interactions within the star's magnetosphere, shedding light on the magnetic activity of ultracool dwarfs.

Star system: 2MASS 0036+1821 | Distance from the Sun: 28.5 light years

The ultracool dwarf LSPM J0036+1821 produces strong radio pulses that mirror the auroral activity seen in our own solar system. Just as Jupiter's powerful magnetic field accelerates electrons to create brilliant polar lights and radio waves, this star exhibits a structured magnetosphere where magnetic fields guide high-energy particles. These emissions provide a way to map the invisible magnetic terrain of stars that are far cooler and smaller than the Sun.

To study this behavior, researchers monitored the star between 2019 and 2023 using the Very Large Array and TESS telescope. By comparing radio signals with optical light measurements, they precisely calculated the star's rotation period and mapped its radio output. The data show stable, repeating pulses that change slightly over time, which experts explain by small shifts in the shape of the magnetic field or the location of active energy zones.

The findings show that the radio emissions are caused by a process known as electron cyclotron maser instability. This occurs when electrons spiral along magnetic field lines, releasing energy in specific patterns. The system exhibits a hybrid structure where a main stable region creates constant emission, while specific active field lines produce the intense, variable bursts observed. This behavior is consistent with processes driven by either internal magnetic dynamics or interactions with an unseen companion, placing this star among the most active magnetic environments known for its type.

Key findings
LSPM J0036+1821 has a rotation period of approximately 3.08 hours.
Radio emissions are highly polarized and show stable, rotationally modulated pulse patterns.
The magnetic activity is driven by electron cyclotron maser instability, similar to Jupiter's magnetosphere.
Short-term radio bursts result from geometric changes in the star's active magnetic field lines.

Scientific study

A Jupiter-like radio aurora in the L3.5 dwarf LSPM J0036+1821 (external link)