CandidateTeegarden's Star system
Teegarden's Star d
A proposed cold outer world reported in 2024: too faint and distant to be confirmed with confidence, and still awaiting independent verification.
- Orbital period
- Proposed 26.1 days
- Distance from the star
- Proposed 0.0791 AU · 11.8 million km
- Minimum mass
- Proposed 0.82 Earth masses
- Radius
- Unknown; no transit detected
- Equilibrium temperature
- About 159 K without an atmosphere
- Status
- Candidate · not yet independently confirmed
- Reported
- 2024 · radial velocity
- Host star
- M7.0V red dwarf · about 0.09 solar masses
- Distance from the Sun
- 12.5 light-years
A tentative outer world
Teegarden's Star d was proposed in a 2024 re-analysis of radial-velocity data, which suggested a small signal on a 26-day orbit beyond the two confirmed planets. The evidence is suggestive but not conclusive, and the planet remains a candidate.
If real, it would have a minimum mass near 0.8 Earth masses and orbit well outside the habitable zone, receiving too little heat for surface liquid water. Its equilibrium temperature would be around 159 K.
Why candidates stay uncertain
Radial-velocity searches look for periodic wobbles in a star's motion, but stars also vary on their own through magnetic activity, spots, and pulsation. A weak planet signal near the star's rotation period or activity cycle can be confused with stellar noise.
That is why astronomers label such detections as candidates until more data arrive from independent instruments or the signal strengthens. Teegarden's Star d is exactly this kind of provisional finding.
What would confirm it
Confirming the planet would require additional radial-velocity observations over several more orbits, preferably with independent instruments and careful activity modelling. A transit would provide size information, but none has been seen, and a 26-day planet this small is unlikely to be caught easily.
- Is the signal a planet or stellar activity?
- If real, what is its true mass and composition?
- Could there be even more planets further out?
Key publications
| Year | Paper | Venue | Link |
|---|---|---|---|
| 2019 | Zechmeister et al., Two temperate Earth-mass planet candidates around Teegarden's Star | A&A 627, A49 | DOI |
| 2024 | Dreizler et al., updated radial-velocity analysis reporting Teegarden's Star d | A&A 684, A117 | ADS |
Values compiled from the NASA Exoplanet Archive and the papers listed above. Teegarden's Star d is listed as a candidate.
Worth knowing
It was reported in 2024 and remains a candidate.
It would be too cold for surface liquid water.
Its proposed year lasts about 26 Earth days.