Astronomers retract polar planet claim around binary brown dwarf 2M1510 after clock error

September 1, 2026 at 07:30 AM2 min

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Astronomers have withdrawn the April 2025 claim of a planet orbiting the binary brown dwarf system 2M1510 at nearly 90 degrees. A later analysis found that inconsistent timestamps in Doppler data created the signal. The backward orbital precession disappeared after correcting the times, leaving the polar planet unconfirmed.

Key Facts

The system 2M1510 lies about 120 light-years from Earth and contains two brown dwarfs, each about 35 times Jupiter's mass.
The two brown dwarfs orbit each other every 20.9 days with an eccentricity of about 0.36.
2M1510 is one of only two known eclipsing double-brown-dwarf systems.
A third brown dwarf, 2M1510 C, lies about 250 astronomical units from the inner pair and was ruled out as the cause of the orbital change.
The 2025 discovery team used radial velocities from the UVES spectrograph on the European Southern Observatory's Very Large Telescope.

The Retracted Signal

In April 2025, astronomers reported that the system 2M1510 might contain the first planet orbiting two brown dwarfs at nearly 90 degrees. The proposed planet was inferred from the elongated orbit of the two brown dwarfs appearing to turn backwards. A later analysis found that inconsistent timestamps in the Doppler data created the signal. After correcting those times, the backward rotation disappeared, leaving the polar planet unconfirmed.

The Binary System

2M1510, short for 2MASS J15104786-2818174, lies about 120 light-years away. Its central pair consists of two young brown dwarfs, each close to 35 times Jupiter's mass. The two bodies travel around their common centre of mass every 20.9 days on an orbit with an eccentricity of about 0.36. From Earth, the geometry allows one brown dwarf to eclipse the other, making 2M1510 one of only two known bona fide eclipsing double-brown-dwarf systems. Eclipses give astronomers unusually direct information about radii and orbital inclination, while spectral lines allow masses to be measured.

The 2025 Analysis

Thomas Baycroft and colleagues used archival and newly collected radial velocities from UVES, the high-resolution spectrograph on the European Southern Observatory's Very Large Telescope. Their paper in Science Advances refined the motion of both brown dwarfs and reported that a model allowing the orbit to precess fitted better than a fixed Keplerian orbit. Apsidal precession is a rotation of an orbit within its own plane, where the ellipse slowly turns so that the direction of closest approach changes over time. General relativity, tidal distortion, rotation and the pull of another body can all contribute to apsidal precession. The unusual part was the direction of the precession, which later turned out to be an artifact of timing errors.