Question: describe the process of spectroscopy to determine the chemical composition of astronomical objects

title: Astronomical spectroscopy
text: z = λ o b s v − λ e m i t λ e m i t ( \ displaystyle z = ( \ frac ( \ lambda _ ( \ mathrm ( obsv ) ) - \ lambda _ ( \ mathrm ( emit ) ) ) ( \ lambda _ ( \ mathrm ( emit ) ) ) ) ) z = f e m i t − f o b s v f o b s v ( \ displaystyle z = ( \ frac ( f_ ( \ mathrm ( emit ) ) - f_ ( \ mathrm ( obsv ) ) ) ( f_ ( \ mathrm ( obsv ) ) ) ) )