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| HD 172167 | |
|---|---|
| Epoch | J2000 |
| Constellation | Lyra |
| Apparencemagnitude | 0.03 |
| Spectraltype | A0V |
| Ra | 18h 36m 56.336s |
| Dec | +38° 47′ 1.29″ |
| Distance | 25.0 ly |
| Mass | 2.1 M☉ |
| Radius | 2.36 R☉ |
| Luminosity | 40 L☉ |
| Temperature | 9,650 K |
| Age | ~450 Myr |
| Othernames | Vega, Alpha Lyrae, HR 7001, HIP 91262 |
HD 172167
HD 172167, commonly known by its traditional name Vega, is a bright A-type main-sequence star in the constellation Lyra. It serves as a fundamental photometric and spectrophotometric standard for systems developed by Friedrich Bessel, Henrietta Swan Leavitt, and institutions such as the International Astronomical Union and Hipparcos. Vega has been central to studies spanning stellar astrophysics, infrared astronomy, and the development of absolute flux calibrations by observatories like Mount Wilson Observatory and Palomar Observatory.
Vega is cataloged under many historical and modern identifiers used by surveys and missions: Henry Draper Catalogue entry HD 172167, Harvard Revised Catalog HR 7001, Hipparcos entry HIP 91262, and identifiers in the Smithsonian Astrophysical Observatory Star Catalog and the Two Micron All-Sky Survey. Its traditional name "Vega" derives from Arabic through medieval translations associated with al-Nasr al-Waqi' and entered European usage during the era of navigators and catalogers like Tycho Brahe and Johannes Hevelius. The star also appears in navigational and astrometric records compiled during expeditions by James Cook and measurements by Friedrich Wilhelm Bessel.
Vega is classified spectrally as A0V and has been used as a baseline for the A0V spectral type used by classifiers such as Annie Jump Cannon and the Harvard Classification Scheme. Its mass and radius estimates derive from models developed by groups at Max Planck Institute for Astronomy and the Geneva Observatory; Vega has roughly 2.1 times the mass of the Sun and a radius about 2.36 times solar. Vega's effective temperature near 9,650 K produces a blue-white spectrum that was characterized in seminal spectrophotometry by George Ellery Hale and colleagues. Its luminosity, on the order of 40 times solar, and surface gravity estimates were refined with interferometric observations from facilities including the Very Large Telescope Interferometer and the Center for High Angular Resolution Astronomy.
In the mid-1980s Vega became the first main-sequence star discovered to exhibit a significant infrared excess by observations with the IRAS mission, provoking follow-up by Spitzer Space Telescope and ground-based observatories like Keck Observatory and Subaru Telescope. The excess emission indicates a circumstellar debris disk composed of dust particles likely produced by collisions of planetesimals analogous to the Kuiper belt in the Solar System. Imaging at submillimeter wavelengths by arrays such as the James Clerk Maxwell Telescope and Atacama Large Millimeter/submillimeter Array has constrained disk structure and asymmetries that informed dynamical models involving perturbations by unseen planetary companions, similar in approach to studies of disks around Fomalhaut and Beta Pictoris.
Vega is a rapid rotator seen nearly pole-on, a conclusion supported by high-resolution spectroscopy and interferometry undertaken by teams at Observatoire de la Côte d'Azur and the CHARA Array. This geometry produces gravity darkening effects described by von Zeipel's theorem and modeled by researchers connected to Geneva stellar evolution models and the MESA code community. Photometric and spectroscopic monitoring by missions and projects such as MOST, TESS, and ground-based campaigns have searched for low-amplitude variability and asteroseismic signals; such investigations connect Vega to broader asteroseismology programs at Harvard-Smithsonian Center for Astrophysics and European Southern Observatory groups seeking nonradial pulsation modes comparable to those in stars observed by Kepler.
Parallax and proper motion for Vega were precisely measured by the Hipparcos mission and later reanalyzed in the context of Gaia astrometry and catalogs maintained by the U.S. Naval Observatory. At a distance of roughly 7.7 parsecs (25 light-years), Vega is one of the nearest luminous A-type stars and is a member of the Local Bubble region of the Milky Way. Kinematic studies have examined Vega's possible membership or association with moving groups studied by teams at Max Planck Institute for Extraterrestrial Physics and the CfA, comparing space motion to groups such as the Ursa Major Moving Group and other nearby young associations investigated in surveys by R. D. Oudmaijer and collaborators.
Vega's role in the history of observational astronomy is extensive: it was among the primary standard stars for magnitude systems formalized by Norman Pogson and later flux standards used by C. A. Müller and the Royal Greenwich Observatory. Its visibility and prominence in northern skies made it important in navigation for explorers like Ferdinand Magellan and surveyors using instruments developed by John Flamsteed and Edmond Halley. Vega features in cultural artifacts, literature, and music, appearing in works connected to authors such as Jules Verne and in science fiction contexts alongside objects like Sirius and Altair. Modern outreach and planetarium programs at institutions like the Smithsonian Institution and American Museum of Natural History continue to present Vega as an exemplar of stellar astrophysics and circumstellar disk research.
Category:Stars Category:A-type main-sequence stars Category:Vega