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Science 5 January 1990:
Vol. 247. no. 4938, pp. 39 - 44
DOI: 10.1126/science.247.4938.39
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Articles

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

Richard R. Radick 1, G. W. Lockwood 2, and Sallie L. Baliunas 3

1 Solar Research Branch of the Geophysics Laboratory (Air Force Systems Command), Sunspot, NM 88349
2 Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001
3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138

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.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Stellar Variability and Global Warming.
R. R. Radick (1994)
Science 266, 1072
   PDF »
Response.
P. Foukal (1994)
Science 266, 1073
   PDF »
Stellar Luminosity Variations and Global Warming.
P. Foukal (1994)
Science 264, 238-239
   Abstract »    PDF »


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