Breakthrough Tracker record

JWST timing variations point to a possible third planet around LP 890-9

Kevin Stevenson and collaborators report statistically significant timing variations across 20 JWST/NIRSpec transits of LP 890-9 b and c. The known two-planet model cannot reproduce the signal, while three-planet models fit substantially better and favor a possible interior planet near 4.4 days.

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Stable ID: astronomy-lp-890-9d-ttv-evidence-2026
Revision: astronomy-lp-890-9d-ttv-evidence-2026.v1
Field: Astronomy · Exoplanet dynamics and transit-timing variations
Evidence: Tier 1 · Peer reviewed: No
Record state: Provisional · Provisional planet candidate
Last checked: 2026-09-07

AI role

The authors report using ChatGPT to assist with Python code, tables, figures and clarity. They do not credit it with originating the planet interpretation.

Record details

Problem or result: Evidence for an additional non-transiting planet in the LP 890-9 system
Authors: Kevin B. Stevenson and twelve collaborators
Institutions: Johns Hopkins APL and University; University of Bristol; UNLV; University of Washington; Space Telescope Science Institute
Result date: Preprint submitted September 4, 2026; submitted to ApJ Letters

Why it matters

A third rocky-system companion would revise the architecture of a nearby temperate M-dwarf system and demonstrates that repeated atmospheric-transit programs can also reveal unseen planets dynamically.

Limits

No transit of LP 890-9 d was detected. The present data do not uniquely determine the architecture, periods from 4.0 to 6.9 days remain plausible, and more high-precision transit times are required.

Sources

Primary: Stevenson et al., evidence for LP 890-9 d via timing variations

Correction and revision history

2026-09-07 — Added after primary-source, scope, status, AI-role and limitation review.

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