Final answer:
An emission spectrum is present in an emission nebula, the sun, and a planetary nebula. These spectra are visible due to the excitation and subsequent release of energy by atoms in the form of light. The Orion Nebula, NGC1763, and the Ring Nebula are examples where this phenomenon is observed.
Step-by-step explanation:
Which of the following are in the emission spectrum? The objects that would display an emission spectrum include a. emission nebula, b. sun, and d. planetary nebula. An emission spectrum is characterized by bright lines or bands on a dark background, which are produced when the electrons in an atom or molecule absorb energy and then release it as light as they return to lower energy states. These spectra are emitted by hot, gaseous objects where the atoms are excited by an energy source.
A. Starlight reflected by dust typically results in a continuous spectrum like that of the original light source, since the dust mainly scatters the light rather than absorbs particular wavelengths to re-emit them. B. A star behind invisible interstellar gas leads to an absorption spectrum, where specific wavelengths are absorbed by the gas, leaving dark lines in the star's continuous spectrum. C. An emission nebula, such as the Orion Nebula or NGC1763, exhibits an emission spectrum because the ultraviolet light from hot stars ionizes the hydrogen atoms in the nebula, and when protons and electrons recombine, they emit light in the visible range. D. Planetary nebulae, like the Ring Nebula (M57) or NGC 7027, also display emission spectra, highlighted by distinct colors representing various elements such as helium, nitrogen, and oxygen, which are at different temperatures and distances from the central star.