The Milky Way and Andromeda are on a Collision Course (it will take a few billion years..). From the persepective of Earth, the approaching Andromeda must have a _____ effect.
a
Redshift
b
Blueshift
c
Elliptical
d
Galactic
b
Blueshift
The correct answer is b) Blueshift.
When two galaxies are on a collision course, the light coming from the approaching galaxy gets compressed, causing a blueshift effect. This means that the wavelength of the light appears shorter, shifting towards the blue end of the electromagnetic spectrum.
The approaching Andromeda must have a blueshift effect from the perspective of Earth.
To understand why, let's first talk about redshift and blueshift. These terms are used to describe the shift in the wavelengths of light from distant objects due to the relative motion between those objects and an observer.
When an object is moving away from the observer, the wavelengths of light it emits appear to be stretched out, causing a shift towards longer wavelengths. This is known as redshift. On the other hand, when an object is moving towards the observer, the wavelengths of light appear compressed, resulting in a shift towards shorter wavelengths. This is called blueshift.
Given that the Milky Way and Andromeda are on a collision course, it means they are moving towards each other. As a result, the light coming from Andromeda will be compressed, causing a shift towards shorter wavelengths, which is referred to as blueshift.