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The Doppler effect
I would think that current evidence suggests that the stars moving away from earth, some of them in far distant galaxies moving at unimaginably high speeds, are going much faster than stars moving toward us. The entire Andromeda galaxy is moving toward us and will collide with us in roughly 5 billion years, and it is not moving anywhere near as fast as the distant retreating galaxies.
Analyzing the spectrum of a star, or galaxy, can provide some useful information, including the temperature of a star, whether a star or galaxy is moving towards us or away from us, and the chemical composition.
If a star is moving towards Earth. The light is seen as 'blue shifted'. As we look at our sun, on the colour spectrum, black lines appear. When looking at distant stars, we can tell if they are moving away from us (Red shift) or getting closer to us (Blue shift). This is because the black lines shift to the red or blue end of the spectrum depending on which direction the star is travelling.
It tells us whether a star (or galaxy, or other object) is moving towards us, or away from us; and how fast.
Astronomers determine whether a star is moving toward or away from the Earth via the Doppler effect. Imagine a motorcycle moving past you. As it drives towards you, it has a higher frequency, and a lower frequency when it drives away. The same thing happens with light. As an object moves towards us, its light has a higher frequency and lower wavelength - this is called blueshift. As an object moves away from us, its light has a lower frequency and higher wavelength - this is called redshift.
Astronomers determine whether a star is moving toward or away from the Earth via the Doppler effect. Imagine a motorcycle moving past you. As it drives towards you, it has a higher frequency, and a lower frequency when it drives away. The same thing happens with light. As an object moves towards us, its light has a higher frequency and lower wavelength - this is called blueshift. As an object moves away from us, its light has a lower frequency and higher wavelength - this is called redshift.
With respect to light, the Doppler effect refers to the apparent change in the frequency (and wavelength) of electromagnetic radiation due to the relative motion of the source relative to the observer. When the source (i.e. a star) moves AWAY from the observer, there is an apparent rarefaction (expansion) in the wavelength of emitted light (i.e. frequency decreases), causing a shift in the emission spectrum towards the red side. This is known as redshifting --> the star is moving away from the observer. The opposite happens in blueshift, when the source moves towards the observer.
Our solar system
47km/h
If a star is moving away from you, the emission lines in its spectrum will be shiftedtoward longer wavelengths/lower frequency/the red end of the spectrum, since theyoriginate on the star itself.But there's no effect on the absorption lines, because those are caused by materialthat's unrelated to the star, and just happens to be in the line of sight between thestar and you.
The star's chemical composition; the star's rotation; pulsations of the star; planets or other invisible objects moving around the star; how quickly the star is moving towards us or away from us.
The Doppler effect
The doppler effect is the change in frequency of a wave for an observer moving relative to the source of the wave. You can measure the location and velocity of a locomotive moving towards or away from your. You can measure a star's location and velocity vector regarding the shift and color emanating from the star light. This is calculated via doppler light equations.
They use a tool called a SPECTROSCOPE.
Yes. If the star is moving away from the Earth, its spectral lines will shift towards the red end of the spectrum. If it is moving towards the Earth, its spectral lines will shift towards the violet end of the spectrum. This is due to Doppler effect.
They can obtain information about what elements are in the star; about the star's temperature; about whether the star is moving towards us or away from us; and partial information about the star's rotation.