Key parameters at a glance

A radius of 2.00 Earth radii
A mass of 7.10 Earth masses
Surface gravity around 1.77 g
An orbital period of 11.231 days
Semi-major axis 0.1046 AU
Equilibrium temperature 1,061 K (788 °C)
Distance from Earth 104.25 light-years
Earth Similarity Index 0.266
Travel time at Voyager 1 speed 1,838,493 years

2 siblings around HR 858

HR 858 d shares its host star with 2 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HR 858 b	Sub-Neptune	2.00	3.55	3.585	1,552	2019
HR 858 c	Super-Earth	1.98	3.80	5.974	1,309	2019
HR 858 d this	Sub-Neptune	2.00	7.10	11.231	1,061	2019

HR 858 d Planet Profile

Physical Specs

Radius

2.00 R⊕

Radius (Jupiter)

0.179 R♃

Mass

7.10 M⊕

Mass (Jupiter)

0.022 M♃

Density

4.90 g/cm³

Surface Gravity

1.77 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.266

HZ Position Inner

Controversial No

Discovery

Year 2019

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#1954of 1978

top 98.7%

This planet

2.00R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-32 c 2.00 R⊕ Kepler-238 f 2.00 R⊕ Kepler-242 c 2.00 R⊕

Metric	Earth	HR 858 d	Jupiter
Radius (R⊕)	1.00	2.00	11.21
Mass (M⊕)	1.00	7.10	317.83
Density (g/cm³)	5.51	4.90	1.33
Surface Gravity (g)	1.00	1.77	2.53
Insolation (S⊕)	1.00	217.00	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	7.100 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 17926

HIP

HIP 13363

TIC

TIC 178155732

Gaia DR2

Gaia DR2 5064574720469473792

Gaia DR3

Gaia DR3 5064574724769475968

System

HR 858

Percentile among Sub-Neptune cohort

Radius 2.001 R⊕ · percentile 1 / cohort 1978

Mass 7.100 M⊕ · percentile 42 / cohort 1978

Orbital period 11.23 d · percentile 39 / cohort 1946

Distance 31.96 pc · percentile 8 / cohort 1975

ESI 0.266 · percentile 20 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

11.231 days

Semi-major axis

0.1046 AU

Eccentricity

0.000

Inclination

87.72 °

Year Length

A year here lasts approximately 11.23 Earth days (3.1% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1046 AU.

Transit Fingerprint

Depth

0.021 %

Duration

3.470 h

Impact parameter b

0.712

Rp / R★

0.015140

Transit midpoint (BJD)

2,458,409.7324

Photometric dip

Transit produces a flux drop of 213 ppm lasting ≈ 3.47 h.

Extended Orbital Architecture

Planet / star radius ratio

0.015140

Semi-major axis / stellar radius

17.930

Impact parameter (b)

0.712

RV semi-amplitude (K)

1.780 m/s

Transit mid-time (BJD)

2,458,409.7324

Long. of periastron (ω)

90.00°

Angular separation (arcsec)

3.27000

Eq. Temperature

1,061K

(788 °C)

Insolation (S⊕)

217.00

Earth = 1.00

Earth Similarity (ESI)

0.266

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

Vanderburg et al. 2019

Instrument

TESS CCD Array

Publication

2019-08

Observation locale

Space

Discovery cohort

Planets confirmed in 2019 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

LP 791-18 c · Sub-Neptune LTT 1445 A b · Super-Earth TOI-270 d · Sub-Neptune L 98-59 d · Super-Earth GJ 357 b · Rocky Terrestrial GJ 143 b · Sub-Neptune HD 23472 c · Super-Earth L 98-59 c · Super-Earth LP 791-18 b · Rocky Terrestrial TOI-270 c · Sub-Neptune HD 23472 b · Sub-Neptune TOI-270 b · Super-Earth

Host System: HR 858

Spectral Class

F-type yellow-white

Effective Temperature

6,354 K — hotter than the Sun (5,778 K)

Estimated Age

2.00 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.258 R☉

Stellar Mass

1.204 M☉

Metallicity [Fe/H]

0.03

Extended Stellar Properties

Surface gravity (log g)

4.300 dex

Stellar density

0.853 g/cm³

Systemic radial velocity

10.07 km/s

Rotational v·sin i

7.50 km/s

Rotation period

6.70 days

Activity index (log R'HK)

-4.926

Metallicity ratio

[Fe/H]

Distance

31.96 parsec

Light-years 104.25 ly

V-band magnitude

6.38 mag

Voyager-speed travel 1,838,493 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

31.257 mas

Total Proper Motion

162.408 mas/yr

PM Right Ascension

123.23 mas/yr

PM Declination

105.79 mas/yr

Galactic Cartesian (pc)

x = 0.628 · y = 0.586 · z = -0.512

Equatorial (J2000)

RA 42.98498° · Dec -30.81406°

Galactic ℓ, b

228.140° · -63.469°

Ecliptic λ, β

27.955° · -44.661°

HTM-20 index

1783300971