Vega

Vega is a bright A-type main-sequence star in the constellation Lyra. It rotates rapidly and is viewed nearly pole-on, making its measured brightness and spectrum depend on latitude.

Gravity darkening: A rotating star’s lower effective gravity near its equator makes that region cooler and dimmer than its poles. Vega’s rapid spin produces strong pole-to-equator temperature and brightness differences.
Photometric system: A standardized method for measuring and comparing the brightness of celestial objects. Vega’s measured brightness anchors the traditional zero point of several systems.
Vega debris disk: A disk of dusty material around Vega, detected through excess infrared emission. The disk made Vega an early and influential case in studies of circumstellar debris.
Lyra: A small northern constellation containing Vega, its brightest star. Vega’s location in Lyra gives it its traditional constellation identity.
Stellar rotation: The spinning of a star about its axis, which can affect its shape, spectrum, and evolution. Vega’s rotation is fast enough to distort its surface and alter observations.
Vega magnitude system: A magnitude scale that assigns Vega a reference brightness, traditionally zero, in each passband. This system uses Vega’s spectrum as the calibration reference for apparent magnitudes.
Vega infrared excess: Infrared emission from Vega beyond what its stellar photosphere alone predicts. Its discovery provided evidence for cool material orbiting the star.
Altair: A bright A-type main-sequence star in Aquila that also rotates rapidly. Like Vega, Altair’s rapid rotation makes its shape and surface brightness latitude-dependent.
Interferometry: A technique that combines waves from separate telescopes to measure fine spatial structure. Interferometric observations helped reveal Vega’s oblate shape and temperature pattern.
Spectral classification: The classification of stars by the patterns and temperatures indicated by their spectra. Vega’s A-type spectrum serves as a familiar example for stellar classification.

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