Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-11-09
Astronomy and Astrophysics
Astrophysics
14 pages, 9 figures, Oral Contribution to IAU 26th General Assembly Joint Discussion 4 - The Ultraviolet Universe: Stars from
Scientific paper
The evolution over time of the magnetic activity and the resulting X-ray and UV coronal and chromospheric emissions of main-sequence dG, dK, and dM stars with widely different ages are discussed. Young cool stars spin rapidly and have correspondingly very robust magnetic dynamos and strong coronal and chromospheric X-ray - UV (XUV) emissions. However, these stars spin-down with time as they lose angular momentum via magnetized winds and their magnetic generated activity and emissions significantly decrease. Studies of dK-dM stars over a wide range of ages and rotations show similar (but not identical) behavior. Particular emphasis is given to discussing the effects that XUV emissions have on the atmospheres and evolution of solar system planets as well as the increasing number of extrasolar planets found hosted by dG-dM stars. The results from modeling the early atmospheres of Venus, Earth and Mars using recently determined XUV irradiances and inferred winds of the young Sun are also briefly discussed. For example, the loss of water from juvenile Venus and Mars can be explained by action of the strong XUV emissions and robust winds of the young Sun. We also examine the effects of strong X-ray and UV coronal and chromospheric emissions (and frequent flares) that dM stars have on possible planets orbiting within their shrunken habitable zones (HZs) - located close to the low luminosity host stars (HZ < ~0.4 AU). Dwarf M stars make interesting targets for further study because of their deep outer convective zones (CZs), efficient dynamos, frequent flares and strong XUV emissions. Furthermore, a large fraction of dM stars are very old (>5 Gyr), which present intriguing possibilities for the development of highly advanced modes of intelligent life on planets that may orbit them.
Engle Scott G.
Guinan Edward F.
No associations
LandOfFree
Evolution over Time of Magentic Dynamo Driven UV & X-ray Emissions of dG-M Stars and Effects on Hosted Planets does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Evolution over Time of Magentic Dynamo Driven UV & X-ray Emissions of dG-M Stars and Effects on Hosted Planets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evolution over Time of Magentic Dynamo Driven UV & X-ray Emissions of dG-M Stars and Effects on Hosted Planets will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-702823