Search results
Results From The WOW.Com Content Network
In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. [7] In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre.
A-F shell stars ranging from A0 to F5. The vast majority of known shell stars are of spectral class B. However, partly because of this many cooler shell stars have remained undetected. [1] The Be phenomenon, and hence the term Be star itself, is now widely applied to similar stars not only of spectral class B, but also A and sometimes O and F.
Comparison of the habitable zones of the Solar System and TRAPPIST-1, an ultracool red dwarf star known to have seven terrestrial planets in stable orbits around the star. Comparison of the habitable zones for different stellar temperatures, with a sample of known exoplanets plus the Earth, Mars, and Venus.
Johannes Kepler's (1571–1630) cosmology eliminated the celestial spheres, but he held that the planets were moved both by an external motive power, which he located in the Sun, and a motive soul associated with each planet. In an early manuscript discussing the motion of Mars, Kepler considered the Sun to cause the circular motion of the planet.
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution
The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red-giant branch in stars whose masses are similar to the Sun's. Horizontal-branch stars are powered by helium fusion in the core (via the triple-alpha process) and by hydrogen fusion (via the CNO cycle) in a shell surrounding the core.
Dynamics of the celestial spheres concerns pre-Newtonian explanations of the causes of the motions of the stars and planets. Dynamical time scale; Ephemeris is a compilation of positions of naturally occurring astronomical objects as well as artificial satellites in the sky at a given time or times. Gravitation
NGC 3923 is an example of a shell galaxy where the stars in its halo are arranged in layers. NGC 3923 has up to 42 shells, the highest number among all shell galaxies, [3] and its shells are much more subtle than those of other shell galaxies. The shells of this galaxy are also symmetrical, while other shell galaxies are more skewed and ...