if a star is moving away from you at constant speed, the absorption lines in its spectrum will.
LectureNotes is correct. If a star is moving away from you at a constant speed, the absorption lines in its spectrum will undergo a specific phenomenon known as “redshift”.
Redshift occurs when there is a shift in the wavelength of light from an object that is moving away from an observer. This phenomenon is a result of the Doppler Effect, which is the change in the observed frequency or wavelength of a wave due to the relative motion between the source of the wave and the observer.
In the case of a star moving away at a constant speed, the absorption lines in its spectrum will be shifted towards longer wavelengths. This means that the wavelengths of light corresponding to specific elements or molecules in the star’s atmosphere will be stretched, resulting in a displacement towards the red end of the electromagnetic spectrum. Hence, the term “redshift”.
By measuring the amount of redshift in the absorption lines of a star’s spectrum, astronomers can determine the speed at which the star is moving away from the observer. This information is crucial for understanding the motion and behavior of celestial objects in the universe, as well as for measuring the expansion of the universe itself.
It’s important to note that the phenomenon of redshift is also observable in other astronomical objects, such as galaxies. The observation of redshift played a critical role in the discovery of the expanding universe and the formulation of the Big Bang theory.