An astronomer takes a spectrum of a nearby star.She finds that its absorption lines all appear at shorter wavelengths than expected from laboratory measurements.She should conclude that the star is:
A) moving toward her.
B) composed of elements not seen on Earth.
C) hotter than her laboratory analogs.
D) obscured by dust.

Question

An astronomer takes a spectrum of a nearby star.She finds that its absorption lines all appear at shorter wavelengths than expected from laboratory measurements.She should conclude that the star is:
A) moving toward her.
B) composed of elements not seen on Earth.
C) hotter than her laboratory analogs.
D) obscured by dust.

Quizplus · Accepted Answer

The shift of the absorption lines towards the blue side of the spectrum indicates that the star is moving towards us, which is known as a blue-shift. This result is due to the Doppler effect.

An Astronomer Takes a Spectrum of a Nearby Star