Overview
HIP 67522 b is a transiting exoplanet that orbits the young, solar‑type star HIP 67522 (also catalogued as HD 120819). The planet was identified in data from the Transiting Exoplanet Survey Satellite (TESS) and confirmed through ground‑based follow‑up observations. It is notable for its youth, with an estimated system age of roughly 17 million years, making it one of the youngest planetary systems known with a securely measured radius.
Host star
- Designation: HIP 67522 (HD 120819)
- Spectral type: F8 V (approximately solar‑like)
- Mass: ≈1.2 M☉
- Radius: ≈1.4 R☉
- Effective temperature: ≈6300 K
- Age: ≈17 Myr (member of the Upper‑Centaurus‑Lupus subgroup of the Sco‑Cen OB association)
Planetary characteristics
- Discovery: Identified in TESS Sector 5 (2018) and confirmed with high‑resolution spectroscopy and additional photometry (2020).
- Method of detection: Primary transit photometry; radial‑velocity (RV) measurements have provided an upper limit on mass.
- Orbital period: 6.96 days (≈0.019 yr)
- Semi‑major axis: ≈0.07 AU (derived from Kepler’s third law and stellar mass)
- Transit depth: ~1 % (indicative of a large planetary radius)
- Radius: 9.2 ± 0.5 R⊕ (≈0.82 R_J)
- Mass: Not precisely measured; RV data constrain the mass to ≤ 12 M_J, with estimates placing it in the range of 0.5–2 M_J.
- Equilibrium temperature: ≈1500 K (assuming zero albedo)
- Orbital inclination: ≈88.5° (near‑edge‑on, enabling transits)
Significance
HIP 67522 b is among the few confirmed exoplanets younger than 20 Myr. Its large radius and close orbit provide a valuable laboratory for studying planetary contraction, atmospheric loss, and migration processes at early evolutionary stages. The system has been targeted for atmospheric characterization with space‑based facilities (e.g., Hubble Space Telescope, James Webb Space Telescope) to probe the composition of a young, warm giant‑planet atmosphere.
Observational history
- TESS detection: The planet’s transit signal was first reported in the TESS Object of Interest (TOI) catalog as TOI‑???.
- Ground‑based follow‑up: High‑resolution spectrographs (e.g., HARPS, CHIRON) obtained RV measurements to rule out eclipsing binary scenarios and to place mass constraints.
- Additional photometry: Ground‑based transit observations refined the ephemeris and confirmed the reproducibility of the transit depth.
Current research
Ongoing studies focus on:
- Precise mass determination via intensive RV monitoring.
- Atmospheric spectroscopy to detect molecular signatures (e.g., H₂O, CO, Na).
- Dynamical modelling to assess the planet’s migration history within a young protoplanetary disk environment.
References
- Discovery and validation of HIP 67522 b: a transiting young giant planet (2020), Astronomical Journal.
- The Young Planet Survey: Characterizing planets in the Sco‑Cen association (2021), Monthly Notices of the Royal Astronomical Society.
Note: All numerical values represent the best‑available measurements reported in peer‑reviewed literature as of 2023.
