Key parameters at a glance

A radius of 3.20 Earth radii
A mass of 0.39 Earth masses
Surface gravity around 0.04 g
An orbital period of 13.176 days
Semi-major axis 0.1189 AU
Equilibrium temperature 1,009 K (736 °C)
Distance from Earth 3,943.75 light-years
Earth Similarity Index 0.113
Travel time at Voyager 1 speed 69,547,990 years

4 siblings around Kepler-33

Kepler-33 c shares its host star with 4 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
Kepler-33 b	Super-Earth	1.74	3.68	5.668	1,336	2011
Kepler-33 c this	Sub-Neptune	3.20	0.39	13.176	1,009	2011
Kepler-33 d	Neptune-like	5.35	3.91	21.776	853	2011
Kepler-33 e	Neptune-like	4.02	5.57	31.784	752	2011
Kepler-33 f	Neptune-like	4.46	9.60	41.029	691	2011

Kepler-33 c Planet Profile

Physical Specs

Radius

3.20 R⊕

Radius (Jupiter)

0.285 R♃

Mass

0.39 M⊕

Mass (Jupiter)

0.001 M♃

Density

0.13 g/cm³

Surface Gravity

0.04 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.113

HZ Position Inner

Controversial No

Discovery

Year 2011

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#348of 1978

top 17.5%

This planet

3.20R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

TOI-4633 c 3.20 R⊕ Kepler-170 b 3.20 R⊕ TOI-332 b 3.20 R⊕

Metric	Earth	Kepler-33 c	Jupiter
Radius (R⊕)	1.00	3.20	11.21
Mass (M⊕)	1.00	0.39	317.83
Density (g/cm³)	5.51	0.13	1.33
Surface Gravity (g)	1.00	0.04	2.53
Insolation (S⊕)	1.00	241.76	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	0.390 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 158935283

Gaia DR2

Gaia DR2 2127355923723254272

Gaia DR3

Gaia DR3 2127355923723254272

System

Kepler-33

Percentile among Sub-Neptune cohort

Radius 3.200 R⊕ · percentile 82 / cohort 1978

Mass 0.390 M⊕ · percentile 0 / cohort 1978

Orbital period 13.18 d · percentile 45 / cohort 1946

Distance 1,209.16 pc · percentile 87 / cohort 1975

ESI 0.113 · percentile 0 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

13.176 days

Semi-major axis

0.1189 AU

Eccentricity

0.000

Inclination

88.19 °

Year Length

A year here lasts approximately 13.18 Earth days (3.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1189 AU.

Transit Fingerprint

Depth

0.030 %

Duration

6.700 h

Impact parameter b

0.440

Rp / R★

0.016020

Transit midpoint (BJD)

2,454,976.6764

Photometric dip

Transit produces a flux drop of 298 ppm lasting ≈ 6.70 h.

Extended Orbital Architecture

Planet / star radius ratio

0.016020

Semi-major axis / stellar radius

13.800

Impact parameter (b)

0.440

Transit mid-time (BJD)

2,454,976.6764

Angular separation (arcsec)

0.09830

Eq. Temperature

1,009K

(736 °C)

Insolation (S⊕)

241.76

Earth = 1.00

Earth Similarity (ESI)

0.113

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

Lissauer et al. 2012

Instrument

Kepler CCD Array

Publication

2012-05

Observation locale

Space

Discovery cohort

Planets confirmed in 2011 at Kepler (12 shown).

Kepler-22 b · Sub-Neptune Kepler-20 d · Sub-Neptune Kepler-26 c · Sub-Neptune Kepler-19 c · Sub-Neptune Kepler-26 b · Sub-Neptune Kepler-28 c · Super-Earth Kepler-10 c · Sub-Neptune Kepler-20 f · Rocky Terrestrial Kepler-42 d · Rocky Terrestrial Kepler-16 b · Neptune-like Kepler-28 b · Super-Earth Kepler-34 b · Neptune-like

Host System: Kepler-33

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,904 K — hotter than the Sun (5,778 K)

Estimated Age

4.27 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.820 R☉

Stellar Mass

1.291 M☉

Metallicity [Fe/H]

0.03

Extended Stellar Properties

Surface gravity (log g)

4.027 dex

Stellar density

0.300 g/cm³

Systemic radial velocity

14.09 km/s

Rotational v·sin i

3.40 km/s

Metallicity ratio

[Fe/H]

Distance

1,209.16 parsec

Light-years 3,943.75 ly

V-band magnitude

14.10 mag

Voyager-speed travel 69,547,990 yr

Multi-band Host Photometry — 16 bands

Astrometric Data

Parallax

0.798 mas

Total Proper Motion

13.130 mas/yr

PM Right Ascension

-1.11 mas/yr

PM Declination

-13.08 mas/yr

Galactic Cartesian (pc)

x = 0.227 · y = -0.656 · z = 0.719

Equatorial (J2000)

RA 289.07753° · Dec 46.00517°

Galactic ℓ, b

77.263° · 15.134°

Ecliptic λ, β

305.681° · 67.096°

HTM-20 index

1983176106