Key parameters at a glance
- A radius of 2.12 Earth radii
- A mass of 8.30 Earth masses
- Surface gravity around 1.85 g
- An orbital period of 9.490 days
- Semi-major axis 0.0805 AU
- Equilibrium temperature 751 K (478 °C)
- Distance from Earth 70.33 light-years
- Earth Similarity Index 0.377
- Travel time at Voyager 1 speed 1,240,183 years
- Almost certainly tidally locked to its host star given the close orbit
HD 97658 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1782of 1978
top 90.0%
This planet
2.12R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | HD 97658 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.12 | 11.21 |
| Mass (M⊕) | 1.00 | 8.30 | 317.83 |
| Density (g/cm³) | 5.51 | 4.80 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.85 | 2.53 |
| Insolation (S⊕) | 1.00 | 41.92 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 8.300 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 7.850 M⊕ | Lower bound from radial-velocity fitting. |
| Computed mass | 7.860 M⊕ | Model-computed mass (e.g. from mass-radius relation). |
Star Catalogue Identifiers
HD
HD 97658
HIP
HIP 54906
TIC
TIC 82308728
Gaia DR2
Gaia DR2 3997075206232885888
Gaia DR3
Gaia DR3 3997075206232885888
System
HD 97658
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 9.49 Earth days (2.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0805 AU.
Transit Fingerprint
Depth
0.071 %
Duration
2.849 h
Impact parameter b
0.390
Rp / R★
0.026700
Transit midpoint (BJD)
2,458,904.9366
Photometric dip
Transit produces a flux drop of 712 ppm lasting ≈ 2.85 h.
Extended Orbital Architecture
Planet / star radius ratio
0.026700
Semi-major axis / stellar radius
24.200
Impact parameter (b)
0.390
RV semi-amplitude (K)
2.800 m/s
Transit mid-time (BJD)
2,458,904.9366
Long. of periastron (ω)
-10.00°
Angular separation (arcsec)
3.73000
Eq. Temperature
751K
(478 °C)
Insolation (S⊕)
41.92
Earth = 1.00
Earth Similarity (ESI)
0.377
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.
Detection Signatures
Transit photometry
A transit dip has been observed from at least one telescope.
Radial velocity
Stellar wobble has been measured spectroscopically.
Discovery Paper
Primary reference
Howard et al. 2011Instrument
HIRES Spectrometer
Publication
2011-03
Observation locale
Ground
Discovery cohort
Planets confirmed in 2010 at W. M. Keck Observatory (12 shown).
Host System: HD 97658
Spectral Class
K-type orange
Effective Temperature
5,212 K — cooler than the Sun (5,778 K)
Estimated Age
3.90 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.728 R☉
Stellar Mass
0.850 M☉
Metallicity [Fe/H]
-0.23
Extended Stellar Properties
Surface gravity (log g)
4.640 dex
Stellar density
3.100 g/cm³
Systemic radial velocity
-1.39 km/s
Rotational v·sin i
0.50 km/s
Activity index (log R'HK)
-4.920
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
46.349 mas
Total Proper Motion
118.032 mas/yr
PM Right Ascension
-107.53 mas/yr
PM Declination
48.66 mas/yr
Galactic Cartesian (pc)
x = -0.883 · y = 0.178 · z = 0.434
Equatorial (J2000)
RA 168.63766° · Dec 25.71060°
Galactic ℓ, b
211.161° · 68.295°
Ecliptic λ, β
159.203° · 19.112°
HTM-20 index
455912135
Observation Record
Photometric series
1
Stellar spectra
3
Transmission spectra
2
Archive notes
2
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