Key parameters at a glance

A radius of 11.50 Earth radii
A mass of 131.90 Earth masses
Surface gravity around 1.00 g
An orbital period of 11.535 days
Semi-major axis 0.1097 AU
Equilibrium temperature 1,228 K (955 °C)
Distance from Earth 259.52 light-years
Earth Similarity Index 0.106
Travel time at Voyager 1 speed 4,576,688 years

HD 1397 b Planet Profile

Physical Specs

Radius

11.50 R⊕

Radius (Jupiter)

1.026 R♃

Mass

131.90 M⊕

Mass (Jupiter)

0.415 M♃

Density

0.48 g/cm³

Surface Gravity

1.00 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.106

HZ Position Inner

Controversial No

Discovery

Year 2018

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#1589of 1771

top 89.7%

This planet

11.50R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

TIC 4672985 b 11.50 R⊕ TOI-2384 b 11.49 R⊕ HATS-71 b 11.48 R⊕

Metric	Earth	HD 1397 b	Jupiter
Radius (R⊕)	1.00	11.50	11.21
Mass (M⊕)	1.00	131.90	317.83
Density (g/cm³)	5.51	0.48	1.33
Surface Gravity (g)	1.00	1.00	2.53
Insolation (S⊕)	1.00	356.00	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	131.899 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 1397

HIP

HIP 1419

TIC

TIC 394137592

Gaia DR2

Gaia DR2 4707634458245031552

Gaia DR3

Gaia DR3 4707634458245031552

System

HD 1397

Percentile among Gas Giant cohort

Radius 11.500 R⊕ · percentile 10 / cohort 1771

Mass 131.899 M⊕ · percentile 10 / cohort 1747

Orbital period 11.54 d · percentile 45 / cohort 1533

Distance 79.57 pc · percentile 31 / cohort 1759

ESI 0.106 · percentile 28 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

11.535 days

Semi-major axis

0.1097 AU

Eccentricity

0.251

Inclination

88.99 °

Year Length

A year here lasts approximately 11.54 Earth days (3.2% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.1097 AU.

Transit Fingerprint

Depth

0.204 %

Duration

8.602 h

Impact parameter b

0.170

Rp / R★

0.045130

Transit midpoint (BJD)

2,458,332.0826

Photometric dip

Transit produces a flux drop of 2,037 ppm lasting ≈ 8.60 h.

Extended Orbital Architecture

Planet / star radius ratio

0.045130

Semi-major axis / stellar radius

10.100

Impact parameter (b)

0.170

RV semi-amplitude (K)

32.000 m/s

Transit mid-time (BJD)

2,458,332.0826

Long. of periastron (ω)

2.10°

Angular separation (arcsec)

1.38000

Eq. Temperature

1,228K

(955 °C)

Insolation (S⊕)

356.00

Earth = 1.00

Earth Similarity (ESI)

0.106

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.

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

Nielsen et al. 2019

Instrument

TESS CCD Array

Publication

2019-03

Observation locale

Space

Discovery cohort

Planets confirmed in 2018 at Transiting Exoplanet Survey Satellite (TESS) (2 shown).

pi Men c · Sub-Neptune HD 219666 b · Neptune-like

Host System: HD 1397

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,521 K — cooler than the Sun (5,778 K)

Estimated Age

4.51 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

2.336 R☉

Stellar Mass

1.324 M☉

Metallicity [Fe/H]

0.29

Extended Stellar Properties

Surface gravity (log g)

3.823 dex

Stellar density

0.147 g/cm³

Systemic radial velocity

30.75 km/s

Rotational v·sin i

2.00 km/s

Metallicity ratio

[Fe/H]

Distance

79.57 parsec

Light-years 259.52 ly

V-band magnitude

7.79 mag

Voyager-speed travel 4,576,688 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

12.539 mas

Total Proper Motion

64.960 mas/yr

PM Right Ascension

64.76 mas/yr

PM Declination

-5.06 mas/yr

Galactic Cartesian (pc)

x = 0.400 · y = 0.031 · z = -0.916

Equatorial (J2000)

RA 4.44716° · Dec -66.35893°

Galactic ℓ, b

308.215° · -50.423°

Ecliptic λ, β

319.963° · -58.523°

HTM-20 index

358104736