Editing Vega (section)

=== Infrared excess ===
One of the early results from the [[Infrared Astronomy Satellite]] (IRAS) was the discovery of [[infrared excess|excess infrared flux]] coming from Vega, beyond what would be expected from the star alone. This excess was measured at [[wavelength]]s of 25, 60 and {{val|100|ul=μm}}, and came from within an angular radius of {{val|10|u=arcseconds}} ({{val|10|u="}}) centered on the star. At the measured distance of Vega, this corresponded to an actual radius of {{val|80|ul=astronomical units}} (AU), where an AU is the average radius of the Earth's orbit around the Sun. It was proposed that this radiation came from a field of orbiting particles with a dimension on the order of a millimetre, as anything smaller would eventually be removed from the system by radiation pressure or drawn into the star by means of [[Poynting–Robertson effect|Poynting–Robertson drag]].<ref name="apj285_808"/> The latter is the result of radiation pressure creating an effective force that opposes the orbital motion of a dust particle, causing it to spiral inward. This effect is most pronounced for tiny particles that are closer to the star.<ref name="mnras_97_423"/>

Subsequent measurements of Vega at {{val|193|u=μm}} showed a lower than expected flux for the hypothesized particles, suggesting that they must instead be on the order of {{val|100|u=μm}} or less. To maintain this amount of dust in orbit around Vega, a continual source of replenishment would be required. A proposed mechanism for maintaining the dust was a disk of coalesced bodies that were in the process of collapsing to form a planet.<ref name=apj285_808/> Models fitted to the dust distribution around Vega indicate that it is a 120-astronomical-unit-radius circular disk viewed from nearly pole-on. In addition, there is a hole in the center of the disk with a radius of no less than {{val|80|u=AU}}.<ref name=mnras314_4_702/>

Following the discovery of an infrared excess around Vega, other stars have been found that display a similar anomaly that is attributable to dust emission. As of 2002, about 400 of these stars have been found, and they have come to be termed "Vega-like" or "Vega-excess" stars. It is believed that these may provide clues to the origin of the [[Solar System]].<ref name=apj124_1_514/>