IAU Rejects 2024 Planet Definition as 73-Light-Year System Exposes Classification Gaps
Updated
Updated · National Geographic · Aug 24
IAU Rejects 2024 Planet Definition as 73-Light-Year System Exposes Classification Gaps
1 articles · Updated · National Geographic · Aug 24
Summary
The IAU declined at its 2024 General Assembly to adopt a new planet definition proposed by Jean-Luc Margot and colleagues, leaving astronomers without a broader rule for newly discovered worlds.
The pressure comes from odd systems such as CD-35 2722, 73 light-years away, where a Jupiter-scale object circles a brown dwarf every 171 days while the brown dwarf orbits its star every 5,000 years.
That discovery, reported last month, prompted its team to label the object an "exosatellite" after debate over whether a Jupiter-size body around a brown dwarf should count as a moon or a planet.
Margot's 2024 framework would judge orbit-clearing quantitatively from mass and distance, separating planets from Pluto-like bodies and counting known exoplanets—including the CD-35 2722 object—as planets.
The dispute traces back to the IAU's 2006 Pluto downgrade and still affects edge cases such as rogue planets and Jupiter-mass binaries, with researchers undecided on whether to resubmit a definition in 2027.