Key parameters at a glance

A radius of 4.35 Earth radii
A mass of 15.20 Earth masses
Surface gravity around 0.80 g
An orbital period of 21.057 days
Semi-major axis 0.1536 AU
Equilibrium temperature 886 K (613 °C)
Distance from Earth 356.66 light-years
Earth Similarity Index 0.221
Travel time at Voyager 1 speed 6,289,723 years

1 sibling around HD 106315

HD 106315 c shares its host star with 1 other confirmed planet. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HD 106315 b	Sub-Neptune	2.44	12.60	9.552	1,153	2017
HD 106315 c this	Neptune-like	4.35	15.20	21.057	886	2017

HD 106315 c Planet Profile

Physical Specs

Radius

4.35 R⊕

Radius (Jupiter)

0.388 R♃

Mass

15.20 M⊕

Mass (Jupiter)

0.048 M♃

Density

1.01 g/cm³

Surface Gravity

0.80 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.221

HZ Position Inner

Controversial No

Discovery

Year 2017

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#481of 574

top 83.6%

This planet

4.35R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

Kepler-1668 b 4.35 R⊕ Kepler-413 b 4.35 R⊕ TOI-470 b 4.34 R⊕

Metric	Earth	HD 106315 c	Jupiter
Radius (R⊕)	1.00	4.35	11.21
Mass (M⊕)	1.00	15.20	317.83
Density (g/cm³)	5.51	1.01	1.33
Surface Gravity (g)	1.00	0.80	2.53
Insolation (S⊕)	1.00	97.00	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	15.200 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 106315

TIC

TIC 56815340

Gaia DR2

Gaia DR2 3698307419878650240

Gaia DR3

Gaia DR3 3698307419878650240

System

HD 106315

Percentile among Neptune-like cohort

Radius 4.350 R⊕ · percentile 16 / cohort 574

Mass 15.200 M⊕ · percentile 7 / cohort 574

Orbital period 21.06 d · percentile 53 / cohort 524

Distance 109.35 pc · percentile 26 / cohort 572

ESI 0.221 · percentile 32 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

21.057 days

Semi-major axis

0.1536 AU

Eccentricity

0.220

Inclination

88.61 °

Year Length

A year here lasts approximately 21.06 Earth days (5.8% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.1536 AU.

Transit Fingerprint

Depth

0.101 %

Duration

4.638 h

Impact parameter b

0.520

Rp / R★

0.030860

Transit midpoint (BJD)

2,457,569.0173

Photometric dip

Transit produces a flux drop of 1,007 ppm lasting ≈ 4.64 h.

Extended Orbital Architecture

Planet / star radius ratio

0.030860

Semi-major axis / stellar radius

25.500

Impact parameter (b)

0.520

RV semi-amplitude (K)

3.430 m/s

Transit mid-time (BJD)

2,457,569.0173

Long. of periastron (ω)

96.00°

Sky-projected obliquity (λ)

-2.68°

Angular separation (arcsec)

1.40000

Eq. Temperature

886K

(613 °C)

Insolation (S⊕)

97.00

Earth = 1.00

Earth Similarity (ESI)

0.221

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.

Transit timing variations

Gravitational interactions from neighbours have been detected.

Discovery Paper

Primary reference

Crossfield et al. 2017

Instrument

Kepler CCD Array

Publication

2017-06

Observation locale

Space

Discovery cohort

Planets confirmed in 2017 at K2 (12 shown).

K2-129 b · Rocky Terrestrial K2-130 b · Super-Earth K2-133 b · Super-Earth K2-128 b · Super-Earth K2-133 c · Super-Earth K2-116 b · Rocky Terrestrial K2-125 b · Sub-Neptune K2-118 b · Sub-Neptune K2-136 d · Super-Earth K2-123 b · Sub-Neptune K2-136 c · Sub-Neptune K2-124 b · Sub-Neptune

Host System: HD 106315

Spectral Class

F-type yellow-white

Effective Temperature

6,327 K — hotter than the Sun (5,778 K)

Estimated Age

4.48 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.296 R☉

Stellar Mass

1.091 M☉

Metallicity [Fe/H]

-0.31

Extended Stellar Properties

Surface gravity (log g)

4.252 dex

Stellar density

0.977 g/cm³

Systemic radial velocity

-3.34 km/s

Rotational v·sin i

12.71 km/s

Metallicity ratio

[Fe/H]

Distance

109.35 parsec

Light-years 356.66 ly

V-band magnitude

8.95 mag

Voyager-speed travel 6,289,723 yr

Multi-band Host Photometry — 15 bands

Astrometric Data

Parallax

9.116 mas

Total Proper Motion

12.280 mas/yr

PM Right Ascension

-2.66 mas/yr

PM Declination

11.99 mas/yr

Galactic Cartesian (pc)

x = -0.998 · y = -0.061 · z = -0.007

Equatorial (J2000)

RA 183.47247° · Dec -0.39344°

Galactic ℓ, b

283.250° · 61.035°

Ecliptic λ, β

183.339° · 1.019°

HTM-20 index

-1618145783