Key parameters at a glance

A radius of 5.44 Earth radii
A mass of 25.50 Earth masses
Surface gravity around 0.86 g
An orbital period of 17.050 days
Semi-major axis 0.1200 AU
Distance from Earth 59.37 light-years
Earth Similarity Index 0.453
Travel time at Voyager 1 speed 1,047,039 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

83 Leonis Bb, also catalogued as HD 99492 b or abbreviated 83 Leo Bb, is an extrasolar planet with a minimum mass of 1.5 Neptune mass. It is located approximately 59 light-years away in the constellation of Leo. The planet was discovered in January 2005 by the California and Carnegie Planet Search team, who use the Doppler spectroscopy method to detect planets. It orbits in a close orbit around the star, completing one orbit in about 17 days. The HARPS-N spectrograph discovered a second Neptune-like exoplanet in 2022 orbiting at 95 days.

Excerpted from Wikipedia · full article

1 sibling around HD 99492

HD 99492 b shares its host star with 1 other confirmed planet. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HD 99492 b this	Neptune-like	5.44	25.50	17.050	—	2004
HD 99492 c	Neptune-like	4.42	17.90	95.233	—	2023

HD 99492 b Planet Profile

Physical Specs

Radius

5.44 R⊕

Radius (Jupiter)

0.486 R♃

Mass

25.50 M⊕

Mass (Jupiter)

0.080 M♃

Density

0.87 g/cm³

Surface Gravity

0.86 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.453

HZ Position Unknown

Controversial No

Discovery

Year 2004

Method Radial Velocity

Facility W. M. Keck Observatory

Telescope 10 m Keck I Telescope

Size rank in cohort

Rank by radius

#322of 574

top 55.9%

This planet

5.44R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

HD 105618 b 5.44 R⊕ KOI-1783.02 5.44 R⊕ HD 190360 c 5.44 R⊕

Metric	Earth	HD 99492 b	Jupiter
Radius (R⊕)	1.00	5.44	11.21
Mass (M⊕)	1.00	25.50	317.83
Density (g/cm³)	5.51	0.87	1.33
Surface Gravity (g)	1.00	0.86	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	25.500 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 99492

HIP

HIP 55848

TIC

TIC 363549734

Gaia DR2

Gaia DR2 3812355294261019904

Gaia DR3

Gaia DR3 3812355294262255104

System

HD 99492

Percentile among Neptune-like cohort

Radius 5.440 R⊕ · percentile 43 / cohort 574

Mass 25.500 M⊕ · percentile 43 / cohort 574

Orbital period 17.05 d · percentile 48 / cohort 524

Distance 18.20 pc · percentile 5 / cohort 572

ESI 0.453 · percentile 81 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

17.050 days

Semi-major axis

0.1200 AU

Eccentricity

0.034

Inclination

— °

Year Length

A year here lasts approximately 17.05 Earth days (4.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1200 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

7.050 m/s

Transit mid-time (BJD)

2,454,297.9400

Long. of periastron (ω)

154.30°

Angular separation (arcsec)

6.59000

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.453

0 = alien, 1 = Earth-identical

Insufficient insolation data. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Marcy et al. 2005

Instrument

HIRES Spectrometer

Publication

2005-01

Observation locale

Ground

Discovery cohort

Planets confirmed in 2004 at W. M. Keck Observatory (6 shown).

HD 183263 b · Gas Giant HD 117207 b · Gas Giant HD 45350 b · Gas Giant HD 188015 b · Gas Giant GJ 436 b · Neptune-like HD 88133 b · Gas Giant

Host System: HD 99492

Spectral Class

K-type orange

Effective Temperature

4,929 K — cooler than the Sun (5,778 K)

Estimated Age

4.80 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.823 R☉

Stellar Mass

0.850 M☉

Metallicity [Fe/H]

0.30

Extended Stellar Properties

Surface gravity (log g)

4.570 dex

Stellar density

2.837 g/cm³

Systemic radial velocity

3.10 km/s

Rotational v·sin i

0.41 km/s

Activity index (log R'HK)

-4.930

Metallicity ratio

[Fe/H]

Distance

18.20 parsec

Light-years 59.37 ly

V-band magnitude

7.57 mag

Voyager-speed travel 1,047,039 yr

Multi-band Host Photometry — 12 bands

Astrometric Data

Parallax

54.906 mas

Total Proper Motion

752.283 mas/yr

PM Right Ascension

-728.28 mas/yr

PM Declination

188.53 mas/yr

Galactic Cartesian (pc)

x = -0.988 · y = 0.144 · z = 0.052

Equatorial (J2000)

RA 171.68969° · Dec 3.00713°

Galactic ℓ, b

259.274° · 58.507°

Ecliptic λ, β

171.178° · -0.532°

HTM-20 index

1625330463

Observation Record

Photometric series

RV measurements

Stellar spectra

Archive notes

Wikipedia → Image: Wikimedia Commons · Kirk39 · GPL

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Explore Related Categories

Neptune-like Planets Radial Velocity Discoveries W. M. Keck Observatory Mission K-type orange Hosts