stars on the main sequence produce energy by fusing hydrogen into helium.
stars on the main sequence produce energy by fusing hydrogen into helium.
stars on the main sequence produce energy by fusing hydrogen into?
helium
main-sequence stars employ two types of hydrogen fusion processes, and the rate of energy generation from each type depends on the temperature in the core region. astronomers divide the main sequence into upper and lower parts, based on which of the two is the dominant fusion process. in the lower main sequence, energy is primarily generated as the result of the proton-proton chain, which directly fuses hydrogen together in a series of stages to produce helium. stars in the upper main sequence have sufficiently high core temperatures to efficiently use the cno cycle. (see the chart.) this process uses atoms of carbon, nitrogen and oxygen as intermediaries in the process of fusing hydrogen into helium.
main sequence
theory predicts that a young cluster of this size should give birth to stars and substellar objects of all spectral types, from huge, hot o stars down to dim brown dwarfs. however, studies of the hyades show that it is deficient in stars at both extremes of mass. at an age of 625 million years, the cluster's main sequence turn-off is about , meaning that all heavier stars have evolved into subgiants, giants, or white dwarfs, while less massive stars continue fusing hydrogen on the main sequence. extensive surveys have revealed a total of 8 white dwarfs in the cluster core, corresponding to the final evolutionary stage of its original population of b-type stars (each about ). the preceding evolutionary stage is currently represented by the cluster's four red clump giants. their present spectral type is k0 iii, but all are actually "retired a stars" of around . an additional "white giant" of type a7 iii is the primary of θ² tauri, a binary system that includes a less massive companion of spectral type a; this pair is visually associated with θ¹ tauri, one of the four red giants, which also has an a-type binary companion.
hyades (star cluster)