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You've probably heard the old classical description of the Doppler effect; if you're standing still near a train track, you can hear the sound of the moving train shifted to a higher frequency as the train is coming toward you, and as the train passes by, you can hear the sound shift down in pitch. The sound waves are bunched up a bit as the train is coming toward you, and you hear the train at an increased tone; when the train passes by and moves away from you, the sound waves are stretched out so you hear the sound at a lower pitch. By measuring the change in the sound, you can calculate quite accurately how fast the train was moving when it passed by.
For stars, we're not listening to a tone; we're measuring the light spectrum, but the principle is the same.
We know what the "normal" frequencies in the starlight would be, for a star not moving towards us or away from us.
We measure specific spectrum patterns called "absorption lines".
We can detect shifts in these patterns.
So, we can measure whether the star is coming toward us (spectral lines at higher frequencies than normal) or is headed away from us (spectrum showing lower frequencies than normal).
When we measure the light - and the Doppler shift - of other stars in our Galaxy, we see a mix of stars moving toward us, and stars moving away from us. This is perfectly normal.
But when we measure the Doppler shift of the light from other galaxies, we see that most of the other galaxies are moving away from us, and that the farther away they are, the faster they are moving!
Note: For those who like a bit of extra detail: The change in the light from distant galaxies is not a true Doppler shift. It's similar, but is caused by the expansion if space itself.
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Explain why some stars in the milky way galaxy have a blue shift Doppler effect and other stars in the milky way have a red shift Doppler?
A blue-shift means an object is moving towards us, a red-shift means it is moving away from us. Blue-shift and red-shift are changes in frequency of the light we receive, due to the relative movement. This is called the Doppler effect.
What are the stars the three stars on this hunters belt?
The three stars that compose the hunters belt in the constellation of Orion are: Alnitak, Alnilam and Mintaka. They are 800 light-years, 1340 light-years and 915 light-years away from us respectively (but, of course, from earths perspective they are in a neat line).
When should you use light years?
Light years are used to measure distance from Earth to distant stars and planets.
Which event formed the galaxies stars and planets?
"And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also."-Genesis 1:16
Are all stars in a constellation the same shape from earth?
They didn't always, but now they do. This is to make charting and reference more universal and easily understood. There are constellations now that cover the entire sky, and the borders between constellations have been defined. There are no gaps of the sky that fall outside of a defined consellation. So any star or other heavenly body can be named starting with the constellation name.
What shift of color do you receive from stars as you get closer?
Blue shift as you get closer because by the Doppler effect, the frequency of the light increases, so the light seems more blue. Using the same logic, there is a red shift for light as you move away from stars.
How can you use Doppler shift in a sentence?
Doppler shift is the change in frequency of a wave that seems to occur as it moves. Scientists study the doppler shift to see whether stars are moving away from or toward our galaxy.
What is the for the change in a stars spectrum when it moves away from earth?
Doppler shift
How is the Doppler effect related to star?
Stars moving toward our solar system display blue shift as the light waves are compressed because their motion relative to us is a positive vector. Stars moving away from us create red shift, as the waves are stretched. This is similar to the Doppler Effect in sound waves.
Explain why some stars in the milky way galaxy have a blue shift Doppler effect and other stars in the milky way have a red shift Doppler?
A blue-shift means an object is moving towards us, a red-shift means it is moving away from us. Blue-shift and red-shift are changes in frequency of the light we receive, due to the relative movement. This is called the Doppler effect.
What is the name for the change in a stars spectrum when it moves away from the earth?
It is called The Doppler Shift
What causes reddening of stars?
Three things: 1. Some stars are of such a temperature that much of the energy is in the form of red light (we call these "M" stars); 2. Doppler effects of rapidly receding stars shift their light towards the red of the spectrum (hence, "red shift"); 3. obscuring dust, either in space or the atmosphere (happens every sundown).
Does the Doppler shift of a Stars proper motion and its distance give us its space velocity?
True
Interstellar reddening is caused by what?
A downward shift in frequency of radiation (perceived as reddening in the visible spectrum) is observed in most stars outside the Milky Way Galaxy. This red shift is assumed to be caused by the stars moving away from our galaxy at a sizable fraction of the speed of light. This shift is similar to the Doppler effect in sound.
How do the spectra of some stars shift?
There is a Doppler shift which results from the relative motion of the star in question, either toward or away from us as we observe it.
How can you measure the time using the stars?
light years
What information using the Doppler shift have you found about the movement of stars and galaxies within your universe?
The universe is expanding.
