Evidence for long-term brightness changes of solar-type stars
Abstract
CHANGES in the brightness of the Sun may introduce further uncertainties into forecasts of global warming by the greenhouse effect. The Sun is known to vary in brightness, on a timescale of years, by 0.1% in phase with changes in magnetic activity during the solar cycle1-3, and variations of up to 0.4%, also correlated with surface magnetic activity, have been found in stars similar to the Sun4. To delimit the magnitude of solar luminosity variations on a timescale of centuries, we have looked at the magnetic behaviour of a number of solar-type stars over several years. Observed in random phases of their long-term variability, they give a sample of the behaviour of a solar-type star over a long period of time. We find indirect evidence that these stars undergo brightness changes of more than the 0.1% observed during the last solar cycle, a result that calls into question the assumption of a constant Sun in calculations using general circulation models for climate forecasting.
- Publication:
-
Nature
- Pub Date:
- December 1990
- DOI:
- 10.1038/348520a0
- Bibcode:
- 1990Natur.348..520B
- Keywords:
-
- Brightness;
- Solar Cycles;
- Stellar Activity;
- Stellar Magnetic Fields;
- Stellar Mass;
- Global Warming;
- Greenhouse Effect;
- Statistical Analysis;
- Astrophysics