blue+shift

blue shift is the shortening of a transmitted signal's wavelength and/or an increase in its frequency,due to the relativistic,Doppler effect which indicates that the object is moving toward the observer. The name comes from the fact that the shorter-wavelength end of the optical spectrum is the blue (or violet) end, hence, when visible light is compacted in wavelength,

The Andromeda Galaxy is moving towards our own Milky Way Galaxy within the Local Gourp thus, when observed from earth, its light is undergoing a blue shift

Cause of blueshift in astronomy These are the known possible causes of blue shift in astronomy:
 * 1) Movement of the source towards us, as seen in
 * 2) the edge of a rotating galaxy moving towards us
 * 3) In blazars which propel relativistic jets towards us
 * 4) Some galaxies and quasarsmedia type="youtube" key="PFreZA5iaMU?fs=1" height="385" width="640"