The Sun in Time: Age, Rotation, and Magnetic Activity of the Sun and Solar-type Stars and Effects on Hosted Planets

Abstract

Multi-wavelength studies of solar analogs (G0-5 V stars) with ages from ~50 Myr to 9 Gyr have been carried out as part of the "Sun in Time" program for nearly 20 yrs. From these studies it is inferred that the young (ZAMS) Sun was rotating more than 10x faster than today. As a consequence, young solar-type stars and the early Sun have vigorous magnetohydrodynamic (MHD) dynamos and correspondingly strong coronal X-ray and transition region / chromospheric FUV-UV emissions. To ensure continuity and homogeneity for this program, we use a restricted sample of G0-5 V stars with masses, radii, T(eff), and internal structure (i.e. outer convective zones) closely matching those of the Sun. From these analogs we have determined reliable rotation-age-activity relations and X-ray - UV (XUV) spectral irradiances for the Sun (or any solar-type star) over time. These XUV irradiance measures serve as input data for investigating the photo-ionization and photo-chemical effects of the young, active Sun on the paleo-planetary atmospheres and environments of solar system planets. These measures are also important to study the effects of these high energy emissions on the numerous exoplanets hosted by solar-type stars of different ages. Recently we have extended the study to include lower mass, main-sequence (dwarf) dK and dM stars to determine relationships among their rotation spin-down rates and coronal and chromospheric emissions as a function of mass and age. From rotation-age-activity relations we can determine reliable ages for main-sequence G, K, M field stars and, subsequently, their hosted planets. Also inferred are the present and the past XUV irradiance and plasma flux exposures that these planets have endured and the suitability of the hosted planets to develop and sustain life.

12 pages, 6 figures; to appear in the proceedings of IAU 258: The Ages of Stars

References in corpus (8)

• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Ages for illustrative field stars using gyrochronology: viability, limitations and errors
• A Re-appraisal of the Habitability of Planets Around M Dwarf Stars
• Patterns of photometric and chromospheric variation among Sun-like stars: A 20-year perspective
• The Differential Rotation of Kappa1 Ceti as Observed by MOST
• A Survey of Chromospheric Activity in the Solar-Type Stars in the Open Cluster M67
• The "Living with a Red Dwarf" Program
• Paradigm shifts in solar dynamo modeling

Cited by in corpus (5)

• Lithium depletion in solar-like stars: no planet connection
• Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"
• The solar wind in time: a change in the behaviour of older winds?
• Modeling the Young Sun's Solar Wind and its Interaction with Earth's Paleomagnetosphere
• The Evolution of the Solar-Stellar Activity