Also found in: Dictionary, Thesaurus, Wikipedia.
Related to faculae: Facular
photosphere, luminous, apparently opaque layer of gases that forms the visible surface of the sun or any other star. The photosphere lies between the dense interior gases and the more attenuated gases of the chromosphere. The incandescent gases of the photosphere, estimated to be at temperatures near 6,000K, are so much brighter than the other layers of the sun that they seem to form a surface. These gases are in a constant state of agitation due to convection currents that reach down to 150,000 mi (241,000 km) below the photosphere. Differences in the density of the gases result in a grainy appearance of the photosphere; the small bright patches, or granules, are several hundred miles in diameter and are constantly shifting. Another feature of the photosphere, observed only near the sun's edge, is the appearance near sunspots of bright, veinlike regions known as faculae.
The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
faculae(fak -yŭ-lee) (singular: facula)
1. Bright patches in the upper part of the solar photosphere that have a higher temperature than their surroundings and occur in areas where there is an enhancement of the relatively weak vertical magnetic field. With the exception of polar faculae, which consist of isolated granules and appear in high heliographic latitudes around the minimum of the sunspot cycle, they are intimately related to sunspots, forming shortly before the spots – in the same vicinity – and persisting for several weeks after their disappearance. Faculae are best seen when near the Sun's limb, where limb darkening renders them more readily visible. They are approximately coincident, albeit at a lower level, with the plages visible in monochromatic light.
2. Bright patches observed on the surface of planetary satellites, especially Ganymede.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006