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The Faint Young Sun Paradox: An observational test of an alternative solar model
Author(s) -
Gaidos Eric J.,
Güdel Manuel,
Blake Geoffrey A.
Publication year - 2000
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl010740
Subject(s) - physics , solar mass , astrophysics , astronomy , luminosity , mars exploration program , planet , stars , minimum mass , solar system , galaxy
We report the results of deep observations at radio (3.6 cm) wavelengths of the nearby solar‐type star π 01 Ursa Majoris with the Very Large Array (VLA) intended to test an alternative theory of solar luminosity evolution. The standard model predicts a solar luminosity only 75% of the present value and surface temperatures below freezing on Earth and Mars at 4 Ga, seemingly in conflict with geologic evidence for liquid water on these planets. An alternative model invokes a compensatory mass loss through a declining solar wind that results in a more consistent early luminosity. The free‐free emission from an enhanced wind around nearby young Sun‐like stars should be detectable at microwave frequencies. Our observations of π 01 UMa, a 300 million year‐old solar‐mass star, place an upper limit on the mass loss rate of 4–5 × 10 −11 M⊙yr −1 . Total mass loss from such a star over 4 Gyr would be less than 6%. If this star is indeed an analog of the early Sun, it casts doubt on the alternative model as a solution to the faint young Sun paradox, particularly for Mars.