Key parameters at a glance

A radius of 12.78 Earth radii
A mass of 263.80 Earth masses
Surface gravity around 1.62 g
An orbital period of 3.942 days
Semi-major axis 0.0488 AU
Equilibrium temperature 1,210 K (937 °C)
Distance from Earth 533.44 light-years
Earth Similarity Index 0.110
Travel time at Voyager 1 speed 9,407,177 years

XO-1 b Planet Profile

Physical Specs

Radius

12.78 R⊕

Radius (Jupiter)

1.140 R♃

Mass

263.80 M⊕

Mass (Jupiter)

0.830 M♃

Density

0.64 g/cm³

Surface Gravity

1.62 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.110

HZ Position Inner

Controversial No

Discovery

Year 2006

Method Transit

Facility XO

Telescope Canon 200mm f/1.8L

Size rank in cohort

Rank by radius

#1118of 1771

top 63.1%

This planet

12.78R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

WASP-97 b 12.78 R⊕ TOI-1820 b 12.78 R⊕ TOI-5232 b 12.78 R⊕

Metric	Earth	XO-1 b	Jupiter
Radius (R⊕)	1.00	12.78	11.21
Mass (M⊕)	1.00	263.80	317.83
Density (g/cm³)	5.51	0.64	1.33
Surface Gravity (g)	1.00	1.62	2.53
Insolation (S⊕)	1.00	321.85	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	263.799 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 236312126

Gaia DR2

Gaia DR2 1316708918505350528

Gaia DR3

Gaia DR3 1316708918505350528

System

XO-1

Percentile among Gas Giant cohort

Radius 12.778 R⊕ · percentile 37 / cohort 1771

Mass 263.799 M⊕ · percentile 28 / cohort 1747

Orbital period 3.94 d · percentile 28 / cohort 1533

Distance 163.55 pc · percentile 46 / cohort 1759

ESI 0.110 · percentile 29 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

3.942 days

Semi-major axis

0.0488 AU

Eccentricity

0.000

Inclination

88.81 °

Year Length

A year here lasts approximately 3.94 Earth days (1.1% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0488 AU.

Transit Fingerprint

Depth

1.800 %

Duration

2.971 h

Impact parameter b

0.240

Rp / R★

0.132600

Transit midpoint (BJD)

2,455,385.5198

Photometric dip

Transit produces a flux drop of 18,000 ppm lasting ≈ 2.97 h.

Extended Orbital Architecture

Planet / star radius ratio

0.132600

Semi-major axis / stellar radius

11.370

Impact parameter (b)

0.240

RV semi-amplitude (K)

116.000 m/s

Transit mid-time (BJD)

2,455,385.5198

Angular separation (arcsec)

0.29800

Eq. Temperature

1,210K

(937 °C)

Insolation (S⊕)

321.85

Earth = 1.00

Earth Similarity (ESI)

0.110

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

Mccullough et al. 2006

Instrument

Apogee CCD Array

Publication

2006-09

Observation locale

Ground

Host System: XO-1

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,750 K — cooler than the Sun (5,778 K)

Estimated Age

0.90 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.880 R☉

Stellar Mass

0.880 M☉

Metallicity [Fe/H]

0.02

Extended Stellar Properties

Surface gravity (log g)

4.510 dex

Stellar density

1.790 g/cm³

Systemic radial velocity

2.56 km/s

Rotational v·sin i

1.11 km/s

Metallicity ratio

[Fe/H]

Distance

163.55 parsec

Light-years 533.44 ly

V-band magnitude

11.25 mag

Voyager-speed travel 9,407,177 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

6.085 mas

Total Proper Motion

22.873 mas/yr

PM Right Ascension

-17.42 mas/yr

PM Declination

14.82 mas/yr

Galactic Cartesian (pc)

x = -0.433 · y = -0.768 · z = 0.472

Equatorial (J2000)

RA 240.54927° · Dec 28.16962°

Galactic ℓ, b

45.853° · 48.021°

Ecliptic λ, β

229.994° · 47.602°

HTM-20 index

-435916487

Observation Record

Photometric series

RV measurements

Transmission spectra

Emission spectra

Archive notes