51 Pegasi b
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| 51 Pegasi b | |
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| Name | 51 Pegasi b |
| Discoverer | Michel Mayor; Didier Queloz |
| Discovered | 1995 |
| Discovery site | Observatoire de Haute-Provence |
| Semimajor | 0.052 AU |
| Period | 4.23 days |
| Mass | ~0.46 M_J |
| Mean radius | ~1.2 R_J (estimated) |
| Surface temp | ~1200–1300 K |
| Star | 51 Pegasi |
51 Pegasi b is a gas giant exoplanet orbiting the Sun-like star 51 Pegasi in the constellation Pegasus. It was the first exoplanet discovered orbiting a main-sequence star, marking a turning point in modern astronomy and exoplanetary science. The detection catalyzed follow-up studies across observatories, institutions, and theoretical groups worldwide.
Discovery
The planet was announced in 1995 by Swiss astronomers Michel Mayor and Didier Queloz using the radial velocity method at the Observatoire de Haute-Provence, a result that influenced projects at the European Southern Observatory and motivated programs at the Keck Observatory, the Anglo-Australian Observatory, and the Hubble Space Telescope community. The finding intersected with work on precision spectroscopy at Geneva Observatory, instrumental development by the European Space Agency, and renewed interest from NASA grants and the Royal Society. The discovery contributed to awards and recognition for Mayor and Queloz, and spurred proposals for missions such as COROT and later Kepler (spacecraft), which broadened exoplanet detection strategies.
Physical characteristics
Observations and models place the planet in the class of hot Jupiters, with a minimum mass comparable to Jupiter as determined from Doppler spectroscopy in Geneva and California Institute of Technology analyses. Radius estimates draw on theoretical models developed at institutions like the Max Planck Institute for Astronomy and the University of Cambridge, constrained by atmospheric retrieval work used for planets studied with the Hubble Space Telescope and the Very Large Telescope. Comparisons have been made with Solar System giants studied by the Jet Propulsion Laboratory and with other exoplanets cataloged by the NASA Exoplanet Archive and the Extrasolar Planets Encyclopaedia. Stellar parameters for 51 Pegasi, refined through spectroscopy at Mount Wilson Observatory and Palomar Observatory, inform mass and radius inferences via stellar evolution models from institutes such as the Harvard–Smithsonian Center for Astrophysics and the University of Geneva.
Orbit and dynamics
With an orbital period of about 4.23 days and a semimajor axis of ~0.052 AU, the planet's close-in orbit was unexpected compared to formation locations predicted by models from the California Institute of Technology and the University of Arizona. Dynamical analyses referencing work by institutions like MIT and Princeton have examined tidal interactions and orbital circularization, while comparisons to multi-planet systems discovered by the Kepler mission and radial velocity surveys at Lick Observatory and Observatory of Haute-Provence have informed migration scenarios. Studies by teams affiliated with the European Southern Observatory and the Carnegie Institution have explored angular momentum exchange, Kozai mechanisms considered in Harvard and Yale dynamical studies, and long-term stability analyses used in N-body simulations developed by groups at Cornell University and the University of California, Berkeley.
Atmosphere and composition
Atmospheric characterization efforts have used high-resolution spectroscopy with instruments on the Very Large Telescope, Keck, and the Hubble Space Telescope to search for absorption signatures similar to those identified in studies of HD 209458 b at the Space Telescope Science Institute. Model atmospheres informed by work at the University of Exeter and the University of Leicester consider molecular absorbers studied by laboratory groups at the Royal Society and spectroscopy databases maintained by NASA. Thermal emission and albedo constraints draw on methods used in analyses by the Spitzer Science Center and studies of irradiation effects led by researchers at the University of Oxford. Proposed detections and upper limits for species such as sodium and carbon monoxide have been discussed in literature from the European Southern Observatory teams and US National Academies workshops on exoplanet atmospheres.
Formation and migration theories
The presence of a close-in giant prompted development of migration theories by groups at the University of Cambridge, University of California, Santa Cruz, and University of Toronto, including disk-driven Type II migration and high-eccentricity migration scenarios explored in reviews from the Max Planck Institute for Astrophysics and Princeton University. Comparisons to planet formation frameworks advanced at the Institute for Advanced Study and observational constraints from submillimeter arrays like ALMA and the Submillimeter Array have informed models of protoplanetary disk interactions. Work by researchers at the University of Michigan and the Carnegie Institution has contrasted in situ formation hypotheses with migration models cited in major review articles and textbooks used at Stanford University and the California Institute of Technology.
Observational studies and methods
Key methods include precision radial velocity pioneered at Geneva Observatory and expanded at observatories such as Lick and Keck, transit searches used by missions like Kepler (spacecraft) and follow-ups with the Hubble Space Telescope, and high-resolution spectroscopy techniques developed at the European Southern Observatory and the Subaru Telescope. Interferometry efforts at the CHARA Array and imaging attempts at the Palomar Observatory employed instruments designed in collaboration with institutions such as Caltech and the Jet Propulsion Laboratory. The planet's discovery and subsequent monitoring influenced instrumentation roadmaps at ESO, NASA, and ESA, and motivated statistical surveys by teams at the Space Telescope Science Institute and the Harvard–Smithsonian Center for Astrophysics.
Cultural and scientific significance
The detection reshaped public and scientific perceptions, influencing outreach by organizations like the Royal Astronomical Society, media coverage by the BBC and The New York Times, and educational programs at universities including Oxford, Cambridge, and Harvard. Scientifically, it catalyzed fields represented by Nobel committees and prize-awarding bodies, led to new collaborations across institutions such as the European Southern Observatory and NASA, and inspired conceptual designs for missions and facilities at ESA, NASA, and national academies. The planet remains a touchstone in exoplanet historiography discussed in works from historians at Columbia University and commentators at the Royal Society.
Category:Exoplanets