Key parameters at a glance

A radius of 2.60 Earth radii
A mass of 6.89 Earth masses
Surface gravity around 1.02 g
An orbital period of 15.572 days
Equilibrium temperature 959 K (686 °C)
Distance from Earth 346.67 light-years
Earth Similarity Index 0.256
Travel time at Voyager 1 speed 6,113,489 years

5 siblings around HIP 41378

HIP 41378 b shares its host star with 5 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HIP 41378 b this	Sub-Neptune	2.60	6.89	15.572	959	2016
HIP 41378 c	Sub-Neptune	2.73	4.40	31.706	757	2016
HIP 41378 g	Sub-Neptune	2.54	7.00	62.060	605	2025
HIP 41378 d	Sub-Neptune	3.54	4.60	278.362	367	2016
HIP 41378 e	Neptune-like	4.92	12.00	369.000	335	2016
HIP 41378 f	Neptune-like	9.20	12.00	542.080	294	2016

HIP 41378 b Planet Profile

Physical Specs

Radius

2.60 R⊕

Radius (Jupiter)

0.232 R♃

Mass

6.89 M⊕

Mass (Jupiter)

0.022 M♃

Density

2.17 g/cm³

Surface Gravity

1.02 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.256

HZ Position Inner

Controversial No

Discovery

Year 2016

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#1040of 1978

top 52.5%

This planet

2.60R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

K2-395 b 2.60 R⊕ Kepler-1821 b 2.59 R⊕ K2-110 b 2.59 R⊕

Metric	Earth	HIP 41378 b	Jupiter
Radius (R⊕)	1.00	2.60	11.21
Mass (M⊕)	1.00	6.89	317.83
Density (g/cm³)	5.51	2.17	1.33
Surface Gravity (g)	1.00	1.02	2.53
Insolation (S⊕)	1.00	140.00	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	6.890 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HIP

HIP 41378

TIC

TIC 366443426

Gaia DR2

Gaia DR2 600698184764497664

Gaia DR3

Gaia DR3 600698184764497664

System

HIP 41378

Percentile among Sub-Neptune cohort

Radius 2.595 R⊕ · percentile 47 / cohort 1978

Mass 6.890 M⊕ · percentile 39 / cohort 1978

Orbital period 15.57 d · percentile 52 / cohort 1946

Distance 106.29 pc · percentile 21 / cohort 1975

ESI 0.256 · percentile 18 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

15.572 days

Semi-major axis

— AU

Eccentricity

—

Inclination

88.80 °

Year Length

A year here lasts approximately 15.57 Earth days (4.3% of a terrestrial year).

Transit Fingerprint

Depth

0.038 %

Duration

4.931 h

Impact parameter b

0.550

Rp / R★

0.018430

Transit midpoint (BJD)

2,457,152.2818

Photometric dip

Transit produces a flux drop of 380 ppm lasting ≈ 4.93 h.

Extended Orbital Architecture

Planet / star radius ratio

0.018430

Semi-major axis / stellar radius

21.000

Impact parameter (b)

0.550

Transit mid-time (BJD)

2,457,152.2818

Eq. Temperature

959K

(686 °C)

Insolation (S⊕)

140.00

Earth = 1.00

Earth Similarity (ESI)

0.256

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.

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

Vanderburg et al. 2016

Instrument

Kepler CCD Array

Publication

2016-08

Observation locale

Space

Discovery cohort

Planets confirmed in 2016 at K2 (12 shown).

K2-72 d · Rocky Terrestrial K2-72 b · Rocky Terrestrial K2-91 b · Rocky Terrestrial K2-72 c · Rocky Terrestrial K2-102 b · Super-Earth K2-90 c · Super-Earth K2-72 e · Super-Earth K2-83 b · Rocky Terrestrial K2-88 b · Rocky Terrestrial K2-80 c · Super-Earth K2-83 c · Super-Earth K2-65 b · Super-Earth

Host System: HIP 41378

Spectral Class

F-type yellow-white

Effective Temperature

6,320 K — hotter than the Sun (5,778 K)

Estimated Age

4.28 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.273 R☉

Stellar Mass

1.160 M☉

Metallicity [Fe/H]

-0.10

Extended Stellar Properties

Surface gravity (log g)

4.294 dex

Stellar density

0.680 g/cm³

Systemic radial velocity

50.42 km/s

Rotational v·sin i

5.60 km/s

Activity index (log R'HK)

-4.780

Metallicity ratio

[Fe/H]

Distance

106.29 parsec

Light-years 346.67 ly

V-band magnitude

8.93 mag

Voyager-speed travel 6,113,489 yr

Multi-band Host Photometry — 12 bands

Astrometric Data

Parallax

9.380 mas

Total Proper Motion

48.143 mas/yr

PM Right Ascension

-48.14 mas/yr

PM Declination

0.06 mas/yr

Galactic Cartesian (pc)

x = -0.587 · y = 0.790 · z = 0.175

Equatorial (J2000)

RA 126.61583° · Dec 10.08037°

Galactic ℓ, b

214.526° · 25.646°

Ecliptic λ, β

126.459° · -8.845°

HTM-20 index

1036383337