Key parameters at a glance

A radius of 13.90 Earth radii
A mass of 242.82 Earth masses
Surface gravity around 1.26 g
An orbital period of 3.243 days
Semi-major axis 0.0391 AU
Equilibrium temperature 1,457 K (1184 °C)
Distance from Earth 3,392.94 light-years
Earth Similarity Index 0.084
Travel time at Voyager 1 speed 59,834,417 years

NGTS-17 b Planet Profile

Physical Specs

Radius

13.90 R⊕

Radius (Jupiter)

1.240 R♃

Mass

242.82 M⊕

Mass (Jupiter)

0.764 M♃

Density

0.50 g/cm³

Surface Gravity

1.26 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.084

HZ Position Inner

Controversial No

Discovery

Year 2021

Method Transit

Facility Next-Generation Transit Survey (NGTS)

Telescope 20 cm NGTS telescope

Size rank in cohort

Rank by radius

#504of 1771

top 28.4%

This planet

13.90R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

WASP-18 b 13.90 R⊕ WASP-124 b 13.90 R⊕ WASP-180 A b 13.90 R⊕

Metric	Earth	NGTS-17 b	Jupiter
Radius (R⊕)	1.00	13.90	11.21
Mass (M⊕)	1.00	242.82	317.83
Density (g/cm³)	5.51	0.50	1.33
Surface Gravity (g)	1.00	1.26	2.53
Insolation (S⊕)	1.00	1,160.00	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	242.821 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 1309019

Gaia DR2

Gaia DR2 4873225513593736960

Gaia DR3

Gaia DR3 4873225513593736960

System

NGTS-17

Percentile among Gas Giant cohort

Radius 13.899 R⊕ · percentile 71 / cohort 1771

Mass 242.821 M⊕ · percentile 26 / cohort 1747

Orbital period 3.24 d · percentile 19 / cohort 1533

Distance 1,040.28 pc · percentile 87 / cohort 1759

ESI 0.084 · percentile 20 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

3.243 days

Semi-major axis

0.0391 AU

Eccentricity

0.000

Inclination

— °

Year Length

A year here lasts approximately 3.24 Earth days (0.9% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0391 AU.

Transit Fingerprint

Duration

3.391 h

Impact parameter b

0.688

Rp / R★

0.095000

Transit midpoint (BJD)

2,458,442.5219

Extended Orbital Architecture

Planet / star radius ratio

0.095000

Semi-major axis / stellar radius

6.280

Impact parameter (b)

0.688

RV semi-amplitude (K)

93.000 m/s

Transit mid-time (BJD)

2,458,442.5219

Angular separation (arcsec)

0.03760

Eq. Temperature

1,457K

(1184 °C)

Insolation (S⊕)

1,160.00

Earth = 1.00

Earth Similarity (ESI)

0.084

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

Tilbrook et al. 2021

Instrument

NGTS CCD array

Publication

2021-03

Observation locale

Ground

Discovery cohort

Planets confirmed in 2021 at Next-Generation Transit Survey (NGTS) (5 shown).

NGTS-14 A b · Neptune-like NGTS-15 b · Gas Giant NGTS-13 b · Gas Giant NGTS-16 b · Gas Giant NGTS-18 b · Gas Giant

Host System: NGTS-17

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,650 K — cooler than the Sun (5,778 K)

Estimated Age

9.22 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.337 R☉

Stellar Mass

1.025 M☉

Metallicity [Fe/H]

0.15

Extended Stellar Properties

Surface gravity (log g)

4.000 dex

Stellar density

0.616 g/cm³

Systemic radial velocity

34.81 km/s

Rotational v·sin i

4.10 km/s

Metallicity ratio

[Fe/H]

Distance

1,040.28 parsec

Light-years 3,392.94 ly

V-band magnitude

14.41 mag

Voyager-speed travel 59,834,417 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

0.932 mas

Total Proper Motion

11.814 mas/yr

PM Right Ascension

-0.19 mas/yr

PM Declination

-11.81 mas/yr

Galactic Cartesian (pc)

x = 0.243 · y = 0.790 · z = -0.562

Equatorial (J2000)

RA 72.90057° · Dec -34.22621°

Galactic ℓ, b

236.488° · -38.605°

Ecliptic λ, β

64.126° · -56.140°

HTM-20 index

1002215164