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Gaia Points to a Fifth HR 8799 Companion
Stellar wobble points to a close-in companion inside the system’s four imaged outer planets.
Summary
Stellar wobble points to a close-in companion inside the system’s four imaged outer planets.
A team combined Gaia absolute astrometry and Hipparcos–Gaia proper-motion anomalies with radial velocities and high-contrast imaging to infer another substellar companion in the HR 8799 system. The allowed orbits span roughly 0.3 to 6 astronomical units, with solutions peaking around 2 to 3 AU and masses near 10 to 14 Jupiters. Dynamical modeling says a low-eccentricity object in that range can coexist with the long-lived resonant chain of the four directly imaged outer planets and may shape the inner edge of the warm debris belt. It is an indirect astrometric inference, not a fifth planet photograph.
Why it matters
Stellar wobble points to a close-in companion inside the system’s four imaged outer planets.
Limits and context
- It is an indirect astrometric inference, not a fifth planet photograph.
Key claims
Stellar wobble points to a close-in companion inside the system’s four imaged outer planets.
Qualification: It is an indirect astrometric inference, not a fifth planet photograph.
Evidence: source-2026-09-21-001
Sources
- arXiv preprint 2609.20996arXiv · primary research
Corrections
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