Question

Evidence of massive amounts of hydrogen gas surrounding some stars comes from

A) observation of the reddening of the spectra of these stars because of absorption of blue light by hydrogen.
B) observation of emission of characteristic red Balmer light from nebulosity around them.
C) theoretical calculations that correctly describe stellar formation by the gravitational contraction of hydrogen gas.
D) observation of the blue glow from scattered light in their reflection nebulae.

Answer 1

The observation of characteristic red Balmer emission lines in nebulae indicates the presence of massive amounts of hydrogen gas around some stars, which is a result of the ionization and recombination processes near hot, young stars.

Step-by-step explanation:

Evidence of massive amounts of hydrogen gas surrounding some stars comes from the observation of emission of characteristic red Balmer light from nebulosity around them. The strongest line in the visible region of the hydrogen spectrum is the red line in the Balmer series. The characteristic red glow in images like those of the Orion Nebula is due to hydrogen emission, indicating that there are hot young stars nearby that ionize the clouds of gas. This process occurs when electrons recombine with protons and move back down into lower energy orbits, at which point emission lines are produced in the Balmer series.