The vast, three-dimensional region of space around the Sun filled with the solar wind and the remnant of the solar magnetic field carried in it. It is bounded by the heliopause, which is estimated to
be 100 astronomical units or more from the Sun. The radius of the heliosphere is expected to vary with the solar cycle. The heliosphere may be very elongated owing to the presence of an interstellar wind of neutral hydrogen flowing from the direction of the Galactic center.
The vast, three-dimensional region of space around the Sun filled with the solar wind and the remnant of the solar magnetic field carried in it. It is bounded by the heliopause, which is estimated to
be 100 astronomical units or more from the Sun. The radius of the heliosphere is expected to vary with the solar cycle. The heliosphere may be very elongated owing to the presence of an interstellar wind of neutral hydrogen flowing from the direction of the Galactic center.
An instrument consisting of a mirror moved by clockwork for tracking the movement of the Sun and reflecting the sunlight into a stationary solar telescope. A heliostat is similar to a coelostat.
The stage in the evolution of a star, after the exhaustion of hydrogen, when the star produces its energy by the fusion of helium into carbon and oxygen.
The stage in the evolution of a star, after the exhaustion of hydrogen, when the star produces its energy by the fusion of helium into carbon and oxygen.
Chemically peculiar stars with very weak helium lines. Examples include 3 Sco, HD 176582, HD 217833, HR 2949, and HD 21699. The He-weak stars do not form a homogeneous group. Some of them display inte
nse Si, or Ti and Sr lines, and are considered a hot extension of the magnetic Ap/Bp stars. Others show overabundances of P and Ga, typically noted for HgMn stars. The star HD 139160 belongs to the non-magnetic subgroup of He-weak stars.