Key parameters at a glance

A radius of 13.20 Earth radii
A mass of 804.08 Earth masses
Surface gravity around 4.61 g
An orbital period of 1,078.000 days
Semi-major axis 2.1000 AU
Distance from Earth 45.00 light-years
Earth Similarity Index 0.385
Travel time at Voyager 1 speed 793,553 years

2 siblings around 47 UMa

47 UMa b 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
47 UMa b this	Gas Giant	13.20	804.08	1,078.000	—	1996
47 UMa c	Gas Giant	14.20	171.62	2,391.000	—	2001
47 UMa d	Gas Giant	13.50	521.22	14,002.000	—	2009

47 UMa b Planet Profile

Physical Specs

Radius

13.20 R⊕

Radius (Jupiter)

1.180 R♃

Mass

804.08 M⊕

Mass (Jupiter)

2.530 M♃

Density

1.92 g/cm³

Surface Gravity

4.61 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.385

HZ Position Unknown

Controversial No

Discovery

Year 1996

Method Radial Velocity

Facility Lick Observatory

Telescope 3.0 m C. Donald Shane Telescope

Size rank in cohort

Rank by radius

#847of 1771

top 47.8%

This planet

13.20R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

HD 12661 c 13.20 R⊕ HD 37605 b 13.20 R⊕ MOA-2009-BLG-387L b 13.20 R⊕

Metric	Earth	47 UMa b	Jupiter
Radius (R⊕)	1.00	13.20	11.21
Mass (M⊕)	1.00	804.08	317.83
Density (g/cm³)	5.51	1.92	1.33
Surface Gravity (g)	1.00	4.61	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	804.080 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 95128

HIP

HIP 53721

TIC

TIC 21535479

Gaia DR2

Gaia DR2 777254360337133312

Gaia DR3

Gaia DR3 777254360337133312

System

47 UMa

Percentile among Gas Giant cohort

Radius 13.200 R⊕ · percentile 49 / cohort 1771

Mass 804.080 M⊕ · percentile 62 / cohort 1747

Orbital period 1,078.00 d · percentile 78 / cohort 1533

Distance 13.80 pc · percentile 2 / cohort 1759

ESI 0.385 · percentile 81 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

1,078.000 days

Semi-major axis

2.1000 AU

Eccentricity

0.032

Inclination

— °

Year Length

A year here lasts about 2.95 Earth years on a nearly circular orbit at a mean orbital distance of 2.1000 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

48.400 m/s

Transit mid-time (BJD)

2,454,415.6000

Long. of periastron (ω)

334.00°

Angular separation (arcsec)

152.00000

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.385

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Butler Marcy 1996

Instrument

Hamilton Echelle Spectrograph

Publication

1996-06

Observation locale

Ground

Discovery cohort

Planets confirmed in 1996 at Lick Observatory (4 shown).

tau Boo b · Gas Giant 70 Vir b · Gas Giant ups And b · Gas Giant 55 Cnc b · Gas Giant

Host System: 47 UMa

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,872 K — hotter than the Sun (5,778 K)

Estimated Age

6.48 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.213 R☉

Stellar Mass

1.060 M☉

Metallicity [Fe/H]

0.04

Extended Stellar Properties

Surface gravity (log g)

4.295 dex

Stellar density

0.837 g/cm³

Systemic radial velocity

11.22 km/s

Rotational v·sin i

2.80 km/s

Activity index (log R'HK)

-5.020

Metallicity ratio

[M/H]

Distance

13.80 parsec

Light-years 45.00 ly

V-band magnitude

5.03 mag

Voyager-speed travel 793,553 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

72.453 mas

Total Proper Motion

322.371 mas/yr

PM Right Ascension

-317.64 mas/yr

PM Declination

55.01 mas/yr

Galactic Cartesian (pc)

x = -0.735 · y = 0.199 · z = 0.649

Equatorial (J2000)

RA 164.86476° · Dec 40.43049°

Galactic ℓ, b

175.783° · 63.368°

Ecliptic λ, β

149.064° · 31.061°

HTM-20 index

-1763902354

Observation Record

Photometric series

RV measurements

Stellar spectra