47 Ursae Majoris

47 Ursae Majoris
Name	47 Ursae Majoris
Other names	47 UMa, HD 95128
Epoch	J2000
Constellation	Ursa Major
Appmag v	5.03
Class	G1V
Parallax	71.39
Dist pc	13.99
Mass	1.03
Radius	1.15
Luminosity	1.12
Age	6–8 Gyr

47 Ursae Majoris is a Sun-like G-type main-sequence star located in the constellation Ursa Major with visual magnitude near 5.0, making it visible to the unaided eye under dark skies. The system is notable for hosting a multi-planet system detected by radial-velocity surveys and has been the subject of studies by observatories and missions concerned with exoplanet demographics and dynamical evolution. Its proximity to the Sun places it within catalogs maintained by institutions such as the Hipparcos and Gaia missions.

Introduction

Situated approximately 14 parsecs from the Solar System, the star appears on charts compiled by the Hipparcos and Henry Draper Catalogue projects and has been observed by facilities including the Keck Observatory, the Lick Observatory, and the European Southern Observatory. As a G1V object its spectral properties have been compared with the Sun and benchmark stars used in the calibration of spectrographs on telescopes like Subaru Telescope and Very Large Telescope. The system’s planets have been analyzed in the context of surveys such as the California Planet Survey and programs using the High Resolution Echelle Spectrometer.

Stellar characteristics

Spectroscopy classifies the star as a G1V main-sequence dwarf; its parameters—mass near 1.03 solar masses and radius about 1.15 solar radii—have been determined via models tied to the Yonsei-Yale and Padova isochrones. Metallicity measurements place it slightly above solar, a trait discussed in statistical studies by teams at University of California, Berkeley and institutes such as the European Southern Observatory. Age estimates, often derived using gyrochronology calibrated against clusters like M67 and isochrone fitting practiced at Harvard–Smithsonian Center for Astrophysics, typically fall in the multi-gigayear range, implying stellar evolution comparable to older field dwarfs cataloged by Mount Wilson Observatory chromospheric activity surveys. Its chromospheric activity has been monitored in datasets associated with programs led by researchers at Carnegie Institution for Science and the Max Planck Institute for Astronomy.

Planetary system

Radial-velocity monitoring revealed at least three giant planets in long-period orbits; these companions have masses in the range of Saturn- to multiple-Jupiter masses when projected (msini) and receive attention in comparative exoplanetology alongside systems like 47 Ursae Majoris's contemporaries such as Upsilon Andromedae and 51 Pegasi. Data from instruments including the High Resolution Echelle Spectrometer, the HIRES instrument, and the ELODIE spectrograph have been used to fit Keplerian models produced by software packages influenced by methods developed at California Institute of Technology and University of Geneva. The architecture—widely spaced, low-eccentricity gas giants—has been compared to models of the Solar System produced by groups at Princeton University and University of Cambridge studying giant planet formation and migration. Studies published through collaborations with researchers at Pennsylvania State University and the University of Hawaii examined potential additional low-mass planets using high-precision radial velocities.

Observational history and discovery

The first planet candidates were reported after long-baseline radial-velocity surveys by teams at Lick Observatory and Keck Observatory; the system featured in early exoplanet catalogs maintained by researchers at Harvard–Smithsonian Center for Astrophysics and the Anglo-Australian Observatory. Follow-up observations using instruments at the Very Large Telescope and comparative analyses by groups at the Max Planck Institute for Astronomy refined orbital parameters. The system’s detection history intersects with milestone surveys such as the California Planet Search and discussion at conferences hosted by organizations like the American Astronomical Society and the International Astronomical Union.

Dynamics and orbital stability

N-body integrations performed by teams at University of California, Santa Cruz and Northwestern University indicate that the planetary configuration is dynamically stable over gigayear timescales for a range of inclinations, though resonant interactions similar to cases studied in GJ 876 and HD 45364 analyses have been explored. Numerical studies using codes developed at Princeton University and the Institut d’Astrophysique de Paris test scenarios of planet–planet scattering and disk-driven migration analogous to models from groups at MIT and University of Arizona. The low eccentricities and wide separations reduce close-encounter probabilities, akin to stability arguments used to explain the architecture of the Solar System and systems examined by the NASA Exoplanet Science Institute.

Habitability and potential for additional planets

Assessments of habitable-zone prospects by researchers at Penn State and the University of California, Santa Cruz consider the system’s habitable zone boundaries derived from models by Kasting and collaborators and later refinements at NASA Goddard Institute for Space Studies. Dynamical studies by teams at Cornell University and University of Arizona explore whether terrestrial planets or moons could exist in stable orbits between or interior to the giant planets, drawing parallels to moon habitability work from Jet Propulsion Laboratory investigators. Direct-imaging prospects with facilities like James Webb Space Telescope, the Very Large Telescope Interferometer, and future missions conceptualized at European Space Agency have been evaluated for detecting additional companions or circumstellar debris analogous to the Kuiper belt detections around nearby stars cataloged by surveys at Spitzer Space Telescope and Herschel Space Observatory.

Category:Stars with exoplanets Category:G-type main-sequence stars