Hot Jupiter Discovered Around 12.3B-Year-Old Metal-Poor Star
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- NASA's TESS satellite identified a transit signal in the light curve of TOI-7169, with planetary nature confirmed by follow-up ground-based imaging and spectroscopy, as detailed in a March 26 arXiv paper
- TOI-7169 b measures 1.475 Jupiter radii and roughly 0.41 Jupiter masses, yielding an extremely low density of 0.159 g/cm³ and earning the inflated-hot-Jupiter classification
- The host star TOI-7169 has a metallicity of −0.72 dex and is estimated at 12.3 billion years old — possibly the oldest and most metal-poor star known to host a transiting giant planet
- The planet completes an orbit every 3.44 days at just 0.043 AU from its star, producing an equilibrium temperature of 1,631 K
- Joshua D. Simon of the Carnegie Institution for Science led the international team that confirmed the discovery, adding to TESS's tally of nearly 8,000 candidate and 765 confirmed exoplanets
- TOI-7169 b is a promising target for future transmission spectroscopy, with its star's brightness and the planet's large radius enabling atmospheric probing to test how heavy-element abundance shapes giant planet properties
Why it matters: TOI-7169 b orbits a star with metallicity of −0.72 dex — far below the metal-rich threshold typically linked to planet formation — potentially establishing a new lower bound for planet-hosting capability and giving astronomers a 12.3-billion-year-old laboratory to test how heavy elements shape giant planet atmospheres and interiors.
