The early history of the solar wind has remained largely a mystery due to the difficulty of detecting winds around young stars that can serve as analogs for the young Sun. Here we report on the detection of a wind from the 500 Myr old solar analog π 1 UMa (G1.5 V), using spectroscopic observations from the Hubble Space Telescope. We detect H i Lyα absorption from the interaction region between the stellar wind and interstellar medium, i.e., the stellar astrosphere. With the assistance of hydrodynamic models of the π 1 UMa astrosphere, we infer a wind only half as strong as the solar wind for this star. This suggests that the Sun and solar-like stars do not have particularly strong coronal winds in their youth.

We present new Hubble Space Telescope observations of H i Lyα absorption toward the F8 V star HD 35296. This line of sight is only a few degrees from the downwind direction of the local interstellar medium flow vector. As a consequence, Lyα absorption from the heliotail is detected in the spectrum, consistent with three previous downwind detections of heliotail absorption. The clustering of the heliotail absorption detections around the downwind direction demonstrates that the heliotail is pointed close to that direction, limiting the extent to which the interstellar magnetic field might be distorting and deflecting the heliotail. We explore this issue further using three-dimensional MHD models of the global heliosphere. The three computed models represent the first three-dimensional MHD models with both a kinetic treatment of neutrals and an extended grid in the tail direction, both of which are necessary to model Lyα absorption downwind. The models indicate only modest heliotail asymmetries and deflections, which are not large enough to be inconsistent with the clustering of heliotail absorption detections around the downwind direction. The models are reasonably successful at reproducing the observed absorption, but they do overpredict the Lyα opacity by a factor of 2-3. We discuss implications of these results in light of observations of the heliotail region from the Interstellar Boundary Explorer mission.

We analyze high-resolution ultraviolet spectra of three nearby exoplanet host stars (HD 192310, HD 9826, and HD 206860) to study interstellar properties along their lines of sight and to search for the presence of astrospheric absorption. Using HST/STIS spectra of the Lyman-α, Mg II, and Fe II lines, we identify three interstellar velocity components in the lines of sight to each star. We can reliably assign eight of the nine components to partially ionized clouds found by Redfield & Linsky (2008) on the basis of the star's location in Galactic coordinates and agreement of measured radial velocities with velocities predicted from the cloud velocity vectors. None of the stars show blue-shifted absorption indicative of an astrosphere, implying that the stars are in regions of ionized interstellar gas. Coupling astrospheric and local interstellar medium measurements is necessary to evaluate the host star electromagnetic and particle flux, which have profound impacts on the atmospheres of their orbiting planets. We present a table of all known exoplanets located within 20 pc of the Sun listing their interstellar properties and velocities predicted from the local cloud velocity vectors.

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