This article was accepted into the corpus but its outbound wikilinks were never NER-processed — typical at the deepest BFS hop or when the run's entity cap was reached. No expansion funnel to show.
| Alpha Serpentis | |
|---|---|
| Name | Alpha Serpentis |
| Other names | Rasalgethi, Ras Algethi, α Ser, Alpha Ser |
| Epoch | J2000 |
| Constellation | Serpens |
| Ra | 15h 30m 00s |
| Dec | +26° 43′ 18″ |
| App mag v | 2.59 |
| Class | K0III |
| B-V | +0.97 |
| U-B | +0.74 |
| Radial v | −22.7 km/s |
| Parallax | 36.78 mas |
| Mass | 1.5–2.0 M☉ |
| Radius | 11–13 R☉ |
| Luminosity | 60–90 L☉ |
| Temperature | 4,700–4,900 K |
| Names | HR 5825, HD 139663, HIP 76669, SAO 83171, FK5 3188 |
Alpha Serpentis is a bright K-type giant star in the constellation Serpens, traditionally known by the names Rasalgethi and Ras Algethi. It is one of the most luminous stars in Serpens, visible to the naked eye and frequently included in historical star catalogs and modern astrometric surveys. Alpha Serpentis serves as a nearby laboratory for studies of stellar evolution, spectroscopy, and circumstellar dynamics.
The traditional proper name Rasalgethi derives from medieval Arabic astronomical nomenclature preserved in works associated with Ptolemy, Al-Sufi, and later European catalogers such as Johann Bayer and John Flamsteed. The Bayer designation α Ser associates the star with the constellation depiction standardized in Bayer's Uranometria and later star atlases by Hevelius and Flamsteed. In modern catalogs the star appears under many catalog identifiers including HD 139663, HIP 76669, HR 5825, and entries in the SAO Catalogue and the FK5 Catalogue. Professional literature also cites astrometric data from the Hipparcos and Gaia missions and spectroscopic parameters from surveys such as the Geneva Observatory compilations and the LAMOST project.
Alpha Serpentis has an apparent visual magnitude near 2.6, making it one of the brighter objects recorded in the Uranometria tradition and observed by visual observers including Tycho Brahe and Galileo Galilei in early modern astronomy. Its precise celestial coordinates place it in Serpens Caput as defined by the International Astronomical Union constellation boundaries adopted in the 20th century. Photometric colors (B−V, U−B) and multiband magnitudes have been measured by missions and observatories such as Johnson photometric system surveys, the Hipparcos photometry pipeline, and the 2MASS. High-resolution spectroscopy from instruments at Keck Observatory, ESO Very Large Telescope, and the McDonald Observatory yields radial velocity, metallicity, and rotational line broadening, while long-term proper motion is tracked by Hipparcos and successive Gaia data releases.
Spectroscopic analyses assign Alpha Serpentis an effective temperature approximately between 4,700 K and 4,900 K and a surface gravity typical of giant stars. Interferometric angular diameter measurements from facilities such as the CHARA Array and the Palomar Testbed Interferometer combined with Hipparcos parallaxes yield a physical radius of order 11–13 solar radii and bolometric luminosity in the range ~60–90 L☉. Mass estimates derived from evolutionary tracks and asteroseismic constraints place the mass roughly 1.5–2.0 times the mass of the Sun; metallicity determinations compare its photospheric abundances to solar values as in studies published by researchers at institutions like Cerro Tololo Inter-American Observatory and the Geneva Observatory. Measured rotational velocities are low, consistent with expansion to the giant phase, and chromospheric activity indicators have been examined in context with surveys conducted by Mount Wilson Observatory and X-ray observatories such as ROSAT.
The spectral classification K0III identifies Alpha Serpentis as a K-type (orange) giant on the Hertzsprung–Russell diagram; researchers reference canonical models by Eddington, Schwarzschild, and modern stellar evolution codes like MESA and PARSEC when interpreting its position. It is generally considered to be on the red giant branch or possibly in a core-helium-burning phase, depending on detailed asteroseismic diagnostics from missions such as Kepler and constraints from Gaia parallaxes. Surface abundance patterns and isotopic ratios, compared against theoretical yields from Iben and contemporary nucleosynthesis studies, inform its prior history of convective mixing and dredge-up events typical of post-main-sequence evolution.
Alpha Serpentis has been examined for multiplicity through radial velocity monitoring, adaptive optics imaging at facilities like Keck and ESO, and speckle interferometry performed at observatories including Calar Alto. Historical catalogs listed possible visual companions recorded by observers such as William Herschel, but modern high-resolution surveys find no bright, close stellar companion; any putative companion would be low-mass or substellar and constrained by limits from radial velocity residuals and direct imaging sensitivity sets. Catalog cross-matches in the Washington Double Star Catalog and astrometric accelerations in Hipparcos and Gaia data provide upper limits on unseen companions.
The traditional name Rasalgethi appears in medieval Islamic star lore preserved in works by Al-Sufi and later Latin translations influential on Renaissance astronomers such as Copernicus and Tycho Brahe. European celestial cartographers including Johann Bayer and John Flamsteed incorporated the star into atlases and catalogs that shaped navigation and early modern astronomy, influencing observers aboard ships of explorers like Ferdinand Magellan and James Cook whose voyages relied on stellar navigation traditions. In modern times Alpha Serpentis features in educational planetarium programming managed by institutions such as the Smithsonian Institution and the Royal Astronomical Society and appears in cultural references preserved in star charts distributed by observatories including Royal Greenwich Observatory.
Category:K-type giants Category:Stars