73.Bok globules small, dark fragments of the interstellar medium.74.The thermal : 1777243
73.Bok globules are small, dark fragments of the interstellar medium.
74.The thermal motions of the atoms in a gas cloud can make it collapse to form a protostar.
75.Molecular clouds are mapped using CO instead of hydrogen because CO is much more abundant than hydrogen in molecular clouds.
76.HII regions are found near stars cooler than 25,000 K because large amounts of ultraviolet photons would totally destroy the hydrogen atoms in the gas.
77.The pressure of a gas depends on the temperature and density of the gas.
78.Some massive stars only live a few million years.
79.Pre-main sequence stars are above and to the right of the main sequence.
80.High mass stars evolve more slowly to the main sequence than lower mass stars.
81.One solar mass stars produce their energy by the set of nuclear reactions called the CNO cycle.
82.The nucleus of the hydrogen atom consists of a single neutron.
83.Stars of spectra type K have strong Balmer lines.
84.The solar neutrino experiments detect about twice as many neutrinos as theory predicts should be detected.