Key parameters at a glance

A radius of 1.98 Earth radii
A mass of 3.80 Earth masses
Surface gravity around 0.97 g
An orbital period of 5.974 days
Semi-major axis 0.0687 AU
Equilibrium temperature 1,309 K (1036 °C)
Distance from Earth 104.25 light-years
Earth Similarity Index 0.200
Travel time at Voyager 1 speed 1,838,493 years

2 siblings around HR 858

HR 858 c 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 this	Super-Earth	1.98	3.80	5.974	1,309	2019
HR 858 d	Sub-Neptune	2.00	7.10	11.231	1,061	2019

HR 858 c Planet Profile

Physical Specs

Radius

1.98 R⊕

Radius (Jupiter)

0.177 R♃

Mass

3.80 M⊕

Mass (Jupiter)

0.012 M♃

Density

2.90 g/cm³

Surface Gravity

0.97 g (Earth)

Classification

Planet Type

Super-Earth

ESI Score 0.200

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

#35of 1176

top 2.9%

This planet

1.98R⊕

Super-Earth median

1.60R⊕

Nearest-size peers

GJ 9827 d 1.98 R⊕ Kepler-59 c 1.98 R⊕ Kepler-85 c 1.98 R⊕

Metric	Earth	HR 858 c	Jupiter
Radius (R⊕)	1.00	1.98	11.21
Mass (M⊕)	1.00	3.80	317.83
Density (g/cm³)	5.51	2.90	1.33
Surface Gravity (g)	1.00	0.97	2.53
Insolation (S⊕)	1.00	512.00	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	3.800 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 Super-Earth cohort

Radius 1.979 R⊕ · percentile 97 / cohort 1176

Mass 3.800 M⊕ · percentile 68 / cohort 1176

Orbital period 5.97 d · percentile 47 / cohort 1164

Distance 31.96 pc · percentile 7 / cohort 1171

ESI 0.200 · percentile 12 / cohort 1176

Orbit & Habitability

Orbital Dynamics

Period

5.974 days

Semi-major axis

0.0687 AU

Eccentricity

0.000

Inclination

86.59 °

Year Length

A year here lasts approximately 5.97 Earth days (1.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0687 AU.

Transit Fingerprint

Depth

0.021 %

Duration

2.843 h

Impact parameter b

0.701

Rp / R★

0.013580

Transit midpoint (BJD)

2,458,415.6334

Photometric dip

Transit produces a flux drop of 209 ppm lasting ≈ 2.84 h.

Extended Orbital Architecture

Planet / star radius ratio

0.013580

Semi-major axis / stellar radius

11.770

Impact parameter (b)

0.701

RV semi-amplitude (K)

1.200 m/s

Transit mid-time (BJD)

2,458,415.6334

Long. of periastron (ω)

90.00°

Angular separation (arcsec)

2.15000

Eq. Temperature

1,309K

(1036 °C)

Insolation (S⊕)

512.00

Earth = 1.00

Earth Similarity (ESI)

0.200

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.

Transit timing variations

Gravitational interactions from neighbours have been detected.

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