When starlight passes through a cold cloud of hydrogen gas, some hydrogen atoms absorb energy, then reradiate it in all directions. As a result, a spectrum of the star shows dark absorption lines at...

When starlight passes through a cold cloud of hydrogen gas, some hydrogen atoms absorb energy, then reradiate it in all

directions. As a result, a spectrum of the star shows dark absorption lines at the energies for which less energy from the star

reaches us. How does the spectrum of dark absorption lines for very cold hydrogen differ from the spectrum of bright

emission lines from very hot hydrogen?