Stellar Activity and Brightness Variations: A Glimpse at the Sun's History

• Published in: Science (American Association for the Advancement of Science) Vol. 247; no. 4938; pp. 39 - 44
• Main Authors: Radick, Richard R., Lockwood, G. W., Baliunas, Sallie L.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 05-01-1990; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Active stars; Analysis; Astronomical photometry; Astronomy; Dwarf stars; Earth, ocean, space; Exact sciences and technology; History; Measurement; Observatories; Solar activity; Star formation; Stars; Stars & galaxies; Stellar characteristics and properties; Stellar evolution; Stellar faculae; Stellar rotation; Sun; Sunspots; Variable stars; Solar activity; Data analysis; Brightness; Star spot; Variations; 11 year-Cycle; Irradiance; Stellar activity; Solar cycle
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.247.4938.39

Radiometric measurements during the past decade from the Solar Maximum Mission and Nimbus 7 satellites have shown that the total solar irradiance varies in step with the sun's 11-year magnetic activity cycle. Stellar observations from the Lowell and Mount Wilson observatories now confirm and elaborate this discovery. These measurements show that older stars similar to the sun tend to become brighter as their magnetic activity level increases, just as the sun does during its 11-year activity cycle. Younger stars, however, tend to become fainter as their magnetic activity level increases. This contrasting behavior suggests that the balance between the competing phenomena that influence solar brightness variability has shifted during the sun's lifetime.