Key parameters at a glance

A radius of 12.50 Earth radii
A mass of 2,926.25 Earth masses
Surface gravity around 18.73 g
An orbital period of 982.850 days
Semi-major axis 2.4760 AU
Distance from Earth 248.60 light-years
Earth Similarity Index 0.394
Travel time at Voyager 1 speed 4,384,107 years

18 Del b Planet Profile

Physical Specs

Radius

12.50 R⊕

Radius (Jupiter)

1.120 R♃

Mass

2,926.25 M⊕

Mass (Jupiter)

9.207 M♃

Density

8.23 g/cm³

Surface Gravity

18.73 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.394

HZ Position Unknown

Controversial No

Discovery

Year 2008

Method Radial Velocity

Facility Okayama Astrophysical Observatory

Telescope 1.88 m Telescope

Size rank in cohort

Rank by radius

#1235of 1771

top 69.7%

This planet

12.50R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

HD 156279 c 12.50 R⊕ HD 33283 b 12.50 R⊕ HD 156279 b 12.50 R⊕

Metric	Earth	18 Del b	Jupiter
Radius (R⊕)	1.00	12.50	11.21
Mass (M⊕)	1.00	2,926.25	317.83
Density (g/cm³)	5.51	8.23	1.33
Surface Gravity (g)	1.00	18.73	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	2,926.246 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 199665

HIP

HIP 103527

TIC

TIC 354489950

Gaia DR2

Gaia DR2 1756741374681702784

Gaia DR3

Gaia DR3 1756741374681702784

System

18 Del

Percentile among Gas Giant cohort

Radius 12.500 R⊕ · percentile 28 / cohort 1771

Mass 2,926.246 M⊕ · percentile 86 / cohort 1747

Orbital period 982.85 d · percentile 77 / cohort 1533

Distance 76.22 pc · percentile 30 / cohort 1759

ESI 0.394 · percentile 84 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

982.850 days

Semi-major axis

2.4760 AU

Eccentricity

0.024

Inclination

— °

Year Length

A year here lasts about 2.69 Earth years on a nearly circular orbit at a mean orbital distance of 2.4760 AU.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.394

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Sato et al. 2008

Instrument

HIDES Echelle Spectrograph

Publication

2008-06

Observation locale

Ground

Discovery cohort

Planets confirmed in 2008 at Okayama Astrophysical Observatory (3 shown).

14 And b · Gas Giant 81 Cet b · Gas Giant 6 Lyn b · Gas Giant

Host System: 18 Del

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

4,980 K — cooler than the Sun (5,778 K)

Estimated Age

1.10 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

8.800 R☉

Stellar Mass

2.100 M☉

Metallicity [Fe/H]

-0.06

Extended Stellar Properties

Surface gravity (log g)

2.870 dex

Systemic radial velocity

4.35 km/s

Metallicity ratio

[Fe/H]

Distance

76.22 parsec

Light-years 248.60 ly

V-band magnitude

5.51 mag

Voyager-speed travel 4,384,107 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

13.092 mas

Total Proper Motion

60.604 mas/yr

PM Right Ascension

-50.03 mas/yr

PM Declination

-34.20 mas/yr

Galactic Cartesian (pc)

x = 0.690 · y = -0.699 · z = 0.188

Equatorial (J2000)

RA 314.60784° · Dec 10.83914°

Galactic ℓ, b

58.691° · -21.975°

Ecliptic λ, β

320.587° · 26.787°

HTM-20 index

96017776

Observation Record

Photometric series

RV measurements

Archive notes