ASTR 1102 Chapter : ASTR 1102 Clem Lect 5
Document Summary
Lines in visible called balmer lines or balmer series . Balmer lines arise due to transitions to/from n=2 orbit. Each element will produce characteristic absorption/emission lines. Astronomers classify stars based on different absorption lines. Spectroscopy measures the precise position of spectral lines. Higher pitch (frequency) when approaching, lower when receding (example: police siren) Approaching waves are squashed, receding are stretched. R: it is shifted slightly to the blue. Y: it is shifted slightly to the red. Light from receding objects is stretched to longer wavelengths (redshift) Light from approaching objects is compressed to shorter wavelengths (blueshift) Fractional change in wavelength equals ratio of relative velocity to speed of light v c. Example: a star approaches us at 0. 1% the speed of light (300 km/s fast!). Redshift v = +300 m/s v = +150 m/s v = 0 m/s. Blueshift v = -300 m/s v = -150 m/s v = 0 m/s.
