Zth2

Zth2 is a designation used for a hypothetical exoplanet candidate identified during a 2022 survey conducted by the European Southern Observatory’s HARPS spectrograph. The object was detected through periodic Doppler shifts in the spectrum of the nearby K-type star HD 219134, suggesting the presence of a planetary mass body with an orbital period of approximately 47.3 days.

Physical characteristics of Zth2 are inferred from limited data. Preliminary mass estimates, based on radial-velocity amplitude, place the planet at roughly 8.5 Earth masses, situating it in the super‑Earth to mini‑Neptune regime. Its semi‑major axis is calculated to be about 0.28 astronomical units, implying a relatively warm environment with an equilibrium temperature estimated near 500 K, assuming a low albedo. No transit events have been observed, so radius and atmospheric composition remain unconstrained.

The scientific interest in Zth2 stems from its position within the transitional mass range where planetary formation models predict a diversity of bulk compositions and atmospheric retention capabilities. Follow‑up observations using high‑resolution spectroscopy and potential direct imaging are planned to refine orbital parameters and assess atmospheric signatures.

Zth2 currently has no confirmed status as an exoplanet, as the detection remains awaiting independent verification. It is catalogued in the Extrasolar Planets Encyclopaedia under provisional entries, pending further observational confirmation.